Distribution of pine wood nematodes and their vectors

Distribution of pine wood nematodes and their vectors | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Distribution of pine wood nematodes and their vectors Chong Kyu Lee, Hyun Kim, Man-Leung Ha This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6261204/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 5 You are reading this latest preprint version Abstract In this study, we investigated the distribution and density of the pine wood nematode Bursaphelenchus xylophilus in recently dead pine trees in coastal and inland regions ofSouth Korea, as well as the mortality rate of pine trees affected by pine wilt disease (PWD). In addition, we examined the seasonal emergence patterns of the Japanese pine sawyer Monochamus alternatus , the primary PWD vector, by monitoring its attraction to aggregation pheromone traps,to assess climate-driven variations in emergence timing. Surveys were conducted in May and June, from 2021 to 2023,across the three PWD-affected regions. In total, 35, 39, and 35 female M. alternatus individuals were collected in 2021, 2022, and 2023, respectively, and47, 55, and 50 males were collected, respectively. A density comparison between B. xylophilus and the co-occurring low-pathogenic B . mucronatus in the felled trees revealed a strong negative correlation, suggesting a potential competitive interaction between the two nematode species. In addition, M. alternatus density was significantly positively correlated with thedaily average temperature ( r = 0.786, 0.744, and 0.755 at Sites 1, 2, and 3, respectively), indicating that rising temperatures are associated with earlier vector emergence. Bursaphelenchus xylophilus Monochamus alternatus nematode pine wood Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Introduction Pine trees (genus Pinus ) are the most cherished and symbolically significant trees in Korea, and are deeply rooted in their culture and history. In addition, they constitute the largest proportion of coniferous forests in the country. Pine trees play a crucial role in various ecological functions, including air purification, forest recreation, and water regulation as green dams (Korea Forest Service, 2023 ). However, global warming, the increasing frequency of large-scale wildfires, and the rapid spread of pine wilt disease (PWD) place pine trees and the entire coniferous forest ecosystem at risk. PWD is caused by the pine wood nematode (PWN; Bursaphelenchus xylophilus ), which enters the vascular system of pine trees, proliferates rapidly, and ultimately causes tree death (Kobayashi et al., 1984 ; Myers, 1988 ). Although pine species are native to North America, the presumed origin of the nematode is generally PWD resistance (Dwinell & Nickle 1989 ; Knowles et al., 1983 ; Sutherland et al., 1991 ). The disease has become a global forest epidemic since its introduction in South Korea, China, Japan, Portugal, and Spain (Abelleira et al., 2011 ; Cheng et al., 1983 ; Enda, 1989 ; Kobayashi et al., 1984 ; Mota et al., 1999 ; Xu et al., 2023 ; Yi et al., 1989 ). Considering that pine wood nematodes (PWN) cannot move on their own, they rely on insect vectors for dispersal. The nematode enters the body of its vector during its larval stage and spreads when vector beetles feed on healthy pine branches or lay eggs beneath the bark, creating entry points for infection (Dwinell & Nickle, 1989 ; Mamiya & Enda, 1972 ). In South Korea, the primary vectors of PWN are the Japanese pine sawyer ( Monochamus alternatus Hope) and northern pine sawyer ( M. saltuarius Gebler), which predominantly infest Pinus red pine ( Pinus densiflora ), black pine ( Pinus thunbergii ), and Korean pine ( Pinus koraiensis ) (Enda, 1989 ; Kishi, 1995 ; Yi et al., 1989 ). Therefore, the occurrence and spread of PWD are closely linked to the ecological dynamics of nematodes and their vectors. The occurrence and spread of PWD are strongly influenced by climatic and environmental factors, including the temperature, precipitation, topography, slope, and elevation of pine habitats (Futai, 2008 ; Park et al., 2013). Temperature plays a crucial role in PWD outbreaks and expansion as it significantly affects the growth, development, and distribution of both PWN and its insect vectors (Futai, 2008 ; Hirata et al., 2017 ; Lu et al., 2005 ). Studies in North America and Japan have shown that PWD occurs in regions where the average annual temperature exceeds 20°C (Rutherford & Webster, 1987 ). In South Korea, the northern and southern distribution limits of M. alternatus correspond to annual mean temperatures of approximately 10°C and 13.2°C, respectively (Kwon et al., 2006 ). To mitigate PWD damage, it is essential to monitor and control the populations of the vector beetles M. alternatus and M. saltuarius (Jung et al., 2018 ). Field surveys, which include monitoring oviposition sites and deploying aggregation pheromone traps, are widely used to track vector activity and population dynamics. These methods help determine the optimal timing for insecticide application and the removal of infected trees, which are crucial steps in controlling PWD outbreaks (Jung et al., 2020 ). To date, little research has been conducted in Korea on the timing of PWN and vector distributions in relation to abnormal high-temperature events and rising average temperatures caused by global warming. To minimize PWD damage to pine trees, it is essential to analyze the factors influencing its occurrence and spread, identify optimal prevention and control periods and high-risk regions, and implement coordinated measures to prevent further outbreaks and expansion. To achieve this goal, we examined the distribution and density of PWN in dead pine trees across coastal and inland regions as well as the mortality rates of infected trees. In addition, we investigated the seasonal emergence patterns of M. alternatus adults by analyzing their attraction to aggregation pheromone traps to determine the climate-driven variations in vector emergence timing. Materials and methods Selection of survey sites Survey sites were selected in areas that experienced moderate to severe PWD damage each year. Coastal sites were chosen from forested regions dominated by black pine trees in Jangseungpo-dong, Ilun-myeon, Geoje-si, Seopo-myeon, and Sacheon-si. Inland sites were selected in forested areas with recurring PWD in Jangjae-dong, Hachon-dong, and Jinju-si (Table 1 , Fig. 1 ). This survey was conducted between 2021 and 2023. Table 1 Geographical coordinates and pine wilt disease (PWD) damage levels at the survey sites. Site Area Location (GPS) PWD damage level Site 1 Geoje-si, Jangseungpo-dong, Irun-myeon 34° 84` 50" N 128° 73’ 02" E 34° 82’ 53" N 128° 71’ 56" E Severe Site 2 Sacheon-si, Seopo-myeon 34° 99’ 34" N 127° 94’ 51" E Severe Site 3 Jinju-si, Jangjae-dong, Hachon-dong 35° 20’ 36" N 128° 10’ 00" E 35° 21’ 98" N 128° 07’ 47" E Moderate Selection of tree species for investigation at each site Three survey plots measuring 20 × 20 m each were established in areas with severe PWD outbreaks. Five dead black pine trees ranging in age from 20 to 40 years were randomly selected from each plot for sampling. The distribution areas were located at elevations ranging from 50 to 200 m. Tree heights ranged from 8 to 14 m, with the diameter at breast height (DBH) varying between 20 and 34 cm. Distribution of PWN and B. mucronatus in felled trees Among the trees that had been felled to control PWD, dead trees were selected for sampling. Following the PWD Control Guidelines (Korea Forest Service, 2016), wood samples were collected from three sections of the tree to assess PWN density in felled trees: the upper canopy (stem and branches at the tree crown), middle canopy (stem in the middle portion of the crown), and lower trunk (stem at breast height). Sampling was conducted from February to March each year from 2021 to 2023 during felling operations for PWD control. The collected samples were processed in the laboratory using the Baermann funnel method (Baermann, 1917 ). Wood samples were finely chopped (< 5 mm), and 20 mL of the extract was obtained from the solution collected at the bottom after 24 h. Thereafter, 10 µL of each extract was placed on a glass slide and observed under a stereomicroscope (Olympus SZ61, Tokyo, Japan) at ×10–×20 magnification. Three replications were conducted for each wood sample to quantify the number of PWN and B. mucronatus . The densities of PWN and B. mucronatus measured throughout the study period were analyzed and compared. Monitoring the emergence of M. alternatus using aggregation pheromone traps Surveys were conducted using aggregation pheromone traps to investigate the emergence period of M . alternatus , the primary vector of PWN. Survey sites were selected in three cities that are heavily affected by PWD: Geoje, Sacheon, and Jinju. At each site, 20 × 20 m plots were established in areas containing dead pine trees, and trees with M. alternatus emergence holes were selected as sample trees. At each site, three multiple-funnel traps (KN, Iksan, Korea) were installed around dead and weakened trees within a 3 m radius, with 4 m spacing between traps. Each trap was baited with 2-(undecyloxy)ethanol, α-pinene, ethanol (EtOH) and an attractant. The survey was conducted biweekly from early May to late June of each year from 2021 to 2023, corresponding to the expected emergence period of M. alternatus . To analyze the effect of temperature on vector emergence time, daily average temperature data (Korea Meteorological Administration, 2023 ) for each survey site were obtained on eight dates in May and June at weekly intervals. Temperature data were analyzed in relation to the number of collected vectors (Table 2 ). Table 2 Daily average temperature (°C) recorded at each survey site on collection dates (2021–2023) Area Year Month/Day 5/6 5/13 5/19 5/27 6/2 6/10 6/17 6/24 Site 1 2021 18.0 19.7 20.1 17.7 21.3 23.2 20.0 21.1 2022 19.0 18.8 19.6 22.2 20.9 20.3 22.6 23.2 2023 15.6 17.1 18.2 22.0 22.8 22.5 23.4 22.1 Site 2 2021 17.9 20.6 20.0 19.2 21.2 22.5 21.5 21.3 2022 20.0 19.9 20.5 22.0 21.4 20.2 22.5 24.7 2023 16.3 18.2 20.0 21.8 23.3 22.1 23.6 22.4 Site 3 2021 13.8 21.0 20.8 17.5 20.9 22.4 21.5 21.8 2022 19.8 20.7 19.6 21.2 21.3 20.2 22.8 25.2 2023 16.5 16.8 20.3 21.9 22.7 22.8 23.8 23.2 Investigation of PWN presence in M. alternatus To investigate the presence of PWN within their vector insects, beetles collected from pheromone traps were brought to the laboratory for examination. After determining the sex of each beetle, their surfaces were rinsed with distilled water before dissection. Thereafter, nematodes within the beetles were isolated using the Baermann funnel method. This process was conducted in triplicate and the number of PWN was quantified. Data analysis All survey results were analyzed using one-way analysis of variance (ANOVA), followed by Duncan’s multiple range test for post hoc comparisons. In addition, correlations between survey results and average temperatures across years, months, and days at each survey site were analyzed (SAS Institute Inc., 2003). Statistical significance was set at 5% (α = 0.05) and all statistical analyses were performed using SAS Ver. 9.1. Results and discussion PWN density in felled black pine trees At each survey site, PWN density was measured in three sections of recently dead trees: the upper canopy, the middle canopy, and the lower trunk. In 2021, the highest PWN density was recorded in the middle canopy at Sites 1 (n = 679.4/g) and 2 (n = 601.3/g). In contrast, the highest density was recorded in the lower trunk of Site 3 (n = 564.9/g). As shown in Fig. 2 , the lowest PWN density was recorded in the lower trunk at Site 1 (n = 585.9/g), upper canopy at Site 2 (n = 567.3/g), and middle canopy at Site 3 (n = 430.5/g) (Site 1: F = 8,282.03, p < 0.001; Site 2: F = 325.71, p < 0.001; Site 3: F = 1,807.13, p < 0.001). In 2022, the highest PWN density was recorded in the lower trunk at Site 1 (n = 521.1/g), upper canopy at Site 2 (n = 672.2/g), and middle canopy at Site 3 (n = 617.1/g). As shown in Fig. 2 , the lowest PWN density was recorded in the middle canopy at Site 1 (n = 461.6/g), lower trunk at Site 2 (n = 600.9/g), and upper canopy at Site 3 (n = 574.0/g) (Site 1: F = 2,204.33, p < 0.001; Site 2: F = 1,589.18, p < 0.001; Site 3: F = 11,859.2, p < 0.001). In 2023, the highest PWN density was recorded in the lower trunk at Site 1 (n = 624.7/g), middle canopy at Site 2 (n = 733.7/g), and upper canopy at Site 3 (n = 713.4/g). As shown in Fig. 2 , the lowest PWN density was recorded in the upper canopy at Site 1 (n = 624.7/g), lower trunk at Site 2 (n = 688.9/g), and lower trunk at Site 3 (n = 681.0/g) (Site 1: F = 1,531.38, p < 0.001; Site 2: F = 5,050.72, p < 0.001; Site 3: F = 771.38, p < 0.001). The PWN density in felled trees did not exhibit a consistent pattern of higher densities in any specific section of the tree. Instead, density varied with the time elapsed since tree death, consistent with previous research indicating that PWN density fluctuates based on moisture content and the tree decay stage (Lee et al., 2023 ; Mamiya, 1983 , 1988 ). Long-dead trees have a lower moisture content, thus offering a less favorable environment for PWN survival. During tree felling for PWD control, prioritizing recently dead trees over long-dead trees may be a more effective strategy for PWD management. Distribution of B. mucronatus in felled trees To investigate the distribution of B. mucronatus , a nematode species closely related to PWN, sampling was performed on three sections (the upper canopy, middle canopy, and lower trunk) of recently dead trees among those felled for PWD control at each survey site. In 2021, the highest B. mucronatus density was recorded in the middle canopy at Site 1 (n = 261.7/g), whereas the lowest density was recorded in the lower trunk (n = 235.7/g). The highest density was recorded at Sites 2 and 3 in the lower trunk (n = 310.7/g and 413.3/g, respectively). As shown in Fig. 3 , the lowest density was recorded in the middle canopy at Sites 2 (n = 225.4/g) and 3 (n = 384/g) (Site 1: F = 11.646, p < 0.009; Site 2: F = 471.92, p < 0.001; Site 3: F = 27.06, p < 0.001). In 2022, the highest B. mucronatus density was recorded in the middle canopy at Site 1 (n = 414.0/g) and Site 2 (n = 211.4/g), and in the upper canopy at Site 3 (n = 287.4/g). As shown in Fig. 3 , the lowest density was recorded in the lower trunk at Site 1 (n = 361.7/g) and Site 3 (n = 225.0/g), and in the upper canopy at Site 2 (n = 183.0/g) (Site 1: F = 87.54, p < 0.001; Site 2: F = 43.90, p < 0.003; Site 3: F = 2.887, p < 0.132). In 2023, the highest B. mucronatus density was observed in the lower trunk at Site 1 (n = 305.7/g), and in the middle canopy at Sites 2 and 3 (n = 227.0/g and n = 267.7/g, respectively). As shown in Fig. 3 , the lowest density was observed in the upper canopy at Site 1 (n = 132.0/g) and in the lower trunk at Site 2 (n = 191.4/g) and Site 3 (n = 225.0/g) (Site 1: F = 357.23, p < 0.001; Site 2: F = 21.35, p < 0.002; Site 3: F = 51.18, p < 0.002). Comparison of PWN and B. mucronatus densities in felled trees A comparative analysis of B. xylophilus (PWN) and B. mucronatus densities in felled trees during the entire survey period revealed a strong negative correlation ( r = ˗0.728, p < 0.01), indicating that B. mucronatus density decreased with increasing distribution of B. xylophilus (Fig. 4 ). These results suggest a potentially competitive interaction between the two species. B. xylophilus may outcompete B. mucronatus in newly infected trees, whereas B. mucronatus , a saprophytic nematode, may persist in later-stage decomposition when the conditions become less favorable for B. xylophilus . Similarly, Park et al. ( 2014 ) reported that nematodes isolated from trees that died within 3 months of PWD, as well as from trees showing disease progression, were all highly virulent, whereas those from felled trees 2–3 years post-mortem exhibited lower virulence. Density of M. alternatus, the PWN vector To investigate the distribution and density of M. alternatus , the primary vector of PWN, pheromone trap surveys were conducted at each site during the emergence period in May and June 2021–2023. 35, 39, and 35 females were collected across the three survey sites in 2021, 2022, and 2023, respectively, and 47, 55, and 50 males were captured, respectively (Fig. 5 ). In 2021, the first collection date was May 13 at all three sites. On this date, one female, one female and two males at Site 2, and one female were collected at Site 1, Site 2, and Site 3, respectively. The peak collection date was June 10, when the highest number of individuals was recorded at all sites. Specifically, three females and seven males were captured at Site 1, four females and seven males at Site 2, and three females and five males at Site 3 (Female: F = 9.36, p < 0.001; Male: F = 19.87, p < 0.001). In 2022, the first collection date was May 6 at all sites. On this date, one female was collected from Site 1, one female and one male from Site 2, and one female from Site 3. The peak collection date was May 27 for Sites 1 and 2, with three females and five males at Site 1, and three females and four males at Site 2. At Site 3, the highest numbers were collected on June 3 and June 17, with two females and four males recorded on both dates (Female: F = 2.21, p < 0.089; Male: F = 6.99, p < 0.006). In 2023, the first collection date was May 20 at all the three sites. One male was collected at Site 1, two females at Site 2, and two males at Site 3. The peak collection dates varied by site: June 17 for Site 1 (four females and five males), June 3 for Site 2 (four females and five males), and June 10 for Site 3 (three females and four males) (Female: F = 10.27, p < 0.001; Male: F = 6.76, p < 0.008). The emergence timing of M. alternatus varied based on the average temperature, supporting previous findings that rising annual average temperatures lead to earlier emergence (Kim et al., 2003 ). In addition, the variation in the first collection dates across the study years and sites was ascribed to temperature differences between the survey regions. Site 1, which experiences a marine climate, had lower average temperatures in April and May than the inland Site 3. This is attributable to cooler spring sea temperatures and frequent sea fog, which result in lower average temperatures in coastal areas. Consequently, emergence at Site 1 was delayed compared to that at Site 3. Across all survey sites, males were collected more frequently than females were. However, previous studies using pheromone traps have reported almost equal male-to-female ratios in M. alternatus (Lee et al., 2021 ; Pajares et al., 2010 ). In contrast, studies on M. saltuarius , another PWN vector, have shown either no sex-dependent differences in attraction (Kim et al., 2016 ) or even female predominance, with females being collected 2.54 times more frequently as males (Lee et al., 2017 ). These discrepancies suggest that environmental factors may play a role in these differences (Jung et al., 2020 ). The pheromone trap used in this study was a commercially available product, whereas previous studies used traps with different pheromone compositions and concentrations, which may account for the variation in the male-to-female collection ratios. In addition, some studies conducted controlled experiments in artificial rearing facilities rather than field conditions, which could also explain the discrepancies. Further field research in the affected forest areas is necessary to reduce the potential confusion arising from these differences. Density of PWN hosted by M. alternatus The number of M. alternatus beetles hosting B. xylophilus was examined based on the sex and collection date. In 2021, 29, 28, and 25 beetles were collected at Sites 1, 2, and 3, respectively, among which 17, 16, and 13 individuals, respectively, were found to host B. xylophilus . In addition, the mean numbers of B. xylophilus hosted per female and male at Site 1 were 2,083.6 (range: 380–5,780) and 3,041.9 (range: 187–7,354), respectively. At Site 2, the mean numbers of B. xylophilus hosted by female and male M. alternatus were 2,902.9 (range: 450–7,247) and 2,741.6 (range: 784–7,869), respectively. At Site 3, the mean numbers of B. xylophilus hosted by female and male M. alternatus were 5,804.4 (range: 587–9,744) and 4,014.4 (range: 254–8,757), respectively (Table 3 ). Table 3 Dates of Monochamus alternatus emergence and the number of Bursaphelenchus xylophilus hosted by male and female M . alternatus in 2021 Date Site 1 Site 2 Site 3 Mean ± SD z (n) Mean ± SD z (n) Mean ± SD z (n) Female Male Female Male Female Male May 6 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 13 5776.3 ± 4.7 c (1) 0 a (0) 0 a (0) 3870.7 ± 4.5 b (1) 3097.3 ± 8.1 b (1) 0 a (0) 20 2575.3 ± 4.5 a (1) 4540.7 ± 9.0 b (1) 4229.3 ± 1583.3 ab (2) 0 a (0) 5864.7 ± 12.9 b (1) 8756.0 ± 4.6 c (1) 27 1781.7 ± 10.2 b (1) 0 (0) 7243.7 ± 3.5c (1) 0 (0) 0 a (0) 0 (0) June 3 1576.3 ± 1312.3 a (2) 4072.2 ± 3594.0 a (2) 720.3 ± 0.6 a (1) 2580.0 ± 1120.0 a (2) 580.7 ± 5.7 a (1) 2603.8 ± 2103.8 a (3) 10 350.4 ± 286.3 a (2) 3497.0 ± 2278.3 a (3) 1723.7 ± 1144.4 a (2) 3200.4 ± 2844.7 a (4) 9743.0 ± 2.6 b (1) 2767.4 ± 2245.4 a (3) 17 1472.7 ± 4.6 a (1) 566.0 ± 3.6 a (1) 454.0 ± 3.6 a (1) 2062.7 ± 2.5 b (1) 7722.0 ± 3465.0 b (1) 7237.3 ± 5.5 c (1) 24 0 (0) 1819.4 ± 1790.3 a (2) 0 (0) 780.3 ± 3.5 a (1) 0 (0) 0 a (0) z Duncan’s multiple range test (DMRT). Means with the same letter within a column are not significantly different ( p < 0.05) In 2022, 32, 32, and 30 beetles were collected at Sites 1, 2, and 3, respectively, among which 20, 15, and 18 individuals, respectively, were found to host B. xylophilus . The mean number of nematodes hosted per female and male M. alternatus at Site 1 was 3,504.4 (range: 240–9,210) and 2,754.3 (range: 421–6,350), respectively. In addition, the mean numbers of nematodes hosted per female and male M. alternatus at Site 2 were 4,629.7 (range: 2,125–8,570) and 3,422.8 (range: 769–7,420), respectively. At Site 3, female and male M. alternatus hosted 3,589.7 (range: 240–7,890) and 4,100.0 (range: 547–9,880) nematodes, respectively (Table 4 ). Table 4 Dates of Monochamus alternatus emergence and the number of Bursaphelenchus xylophilus hosted by male and female M . alternatus in 2022 Date Site1 Site2 Site3 Mean ± SD z (n) Mean ± SD z (n) Mean ± SD z (n) Female Male Female Male Female Male May 6 4749.7 ± 4.5 b (1) 0 a (0) 0 a (0) 4007.7 ± 0.6 b (1) 5604.0 ± 3.6 c (1) 0 a (0) 13 0 a (0) 3581.0 ± 5.7 c (1) 2124.7 ± 4.5 c (1) 0 a (0) 242.4 ± 3.2 b (1) 2779.7 ± 6.5 b (1) 20 2994.0 ± 2641.9 a (2) 0 a (0) 7670.7 ± 1558.6 b (1) 0 a (0) 0 a (0) 9557.3 ± 6.4 b (1) 27 2171.2 ± 193.0 a (2) 3560.5 ± 3063.4 a (2) 4854.7 ± 2.3 a (1) 5332.3 ± 2290.2 a (2) 4298.5 ± 3936.8 a (2) 3254.3 ± 3.8 a (1) June 3 5122.0 ± 2.6 b (1) 2193.8 ± 1159.5 a (2) 3279.7 ± 433.1 a (2) 6565.7 ± 4.2b (1) 3764.3 ± 4.0 a (1) 7553.2 ± 3610.5 b (2) 10 9214.3 ± 4.0 c (1) 2264.3 ± 5.1 b (1) 0 a (0) 2992.3 ± 4.0 c (1) 4320.3 ± 704.4 b (2) 0 a (0) 17 1711.3 ± 3.5 c (1) 1491.8 ± 1171.9 a (1) 0 a (0) 1618.2 ± 182.1 a (2) 905.3 ± 2.9 b (1) 3432.0 ± 1808.9 b (2) 24 1959.8 ± 1890.9 a (2) 3600.0 ± 2112.8 b (2) 5664.3 ± 6.0 b (1) 1668.2 ± 990.5 a (2) 4563.3 ± 4.2 b (1) 837.0 ± 320.3 a (1) z Duncan’s multiple range test (DMRT). Means with the same letter within a column are not significantly different ( p < 0.05). In 2023, 32, 29, and 24 beetles were collected at Sites 1, 2, and 3, respectively, among which 20, 16, and 14 individuals, respectively, were found to host B. xylophilus . At Site 1, female and male M. alternatus hosted 2,646.1 (range: 240–8,080) and 2,576.6 (range: 185–7,160) nematodes, respectively. In addition, female and male M. alternatus hosted 2,949.4 (range: 919–6,280) and 2,797.6 (range: 210–8,870) nematodes, respectively, at Site 2. At Site 3, female M. alternatus hosted an average of 1,226.3 nematodes (range: 80–2,950), and male M. alternatus hosted an average of 4,554.3 nematodes (range: 120–11,260) (Table 5 ). Table 5 Dates of Monochamus alternatus emergence and the number of Bursaphelenchus xylophilus hosted by male and female M . alternatus in 2023 Date Site1 Site2 Site3 Mean ± SD z (n) Mean ± SD z (n) Mean ± SD z (n) Female Male Female Male Female Male May 6 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 13 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 20 0 a (0) 2234.7 ± 1.5 ab (1) 4359.5 ± 2101.2 b (2) 0 a (0) 0 a (0) 7430.3 ± 4175.1 b (2) 27 5565.7 ± 6.0 c (1) 1914.0 ± 1898.8 a (2) 2772.0 ± 2.6 a (1) 8865.3 ± 4.5 b (1) 2948.3 ± 2.9 b (1) 3146.7 ± 3313.0 a (2) June 3 1129.7 ± 352.4 a (2) 4632.3 ± 2742.3 a (2) 2238.2 ± 1449.8 a (2) 2586.3 ± 2445.7 a (3) 864.0 ± 3.6 a (1) 2814.3 ± 299.8 a (2) 10 7838.8 ± 467.9 c (1) 1469.2 ± 2063.0 a (3) 3483.0 ± 7.5 b (1) 2670.3 ± 0.6 ab (1) 658.0 ± 334.5 a (2) 5077.3 ± 15.0 b (1) 17 2372.0 ± 2101.2 a (2) 3508.3 ± 2841.7 b (3) 1158.7 ± 33.5 a (1) 1595.0 ± 900.5 ab (2) 1466.8 ± 1518.8 a (2) 0 a (0) 24 1053.5 ± 891.9 a (1) 2554.0 ± 18.5 c (1) 0 a (0) 1342.7 ± 735.8 b (2) 526.7 ± 6.1 a (1) 0 a (0) z Duncan’s multiple range test (DMRT). Means with the same letters within a column are not significantly different ( p < 0.05). The average proportion of M. alternatus individuals harboring B. xylophilus across all sites was 57%, which was significantly higher than that reported in a previous nationwide survey using pheromone traps (National Institute of Forest Science, 2023 ). This discrepancy is likely due to differences in sampling methods: randomly selected pine forests versus PWD-affected pine forests. Previous research has shown that the density of B. xylophilus hosted by M . alternatus varies by region, with a maximum of 298,000 nematodes per beetle (Kishi, 1995 ). In addition, the proportion of beetles that emerged from B. xylophilus -infested pine trees harboring B. xylophilus was 38.3%, with an average of 20,083.1 nematodes per beetle (range: 56–128,700) (Kim et al., 2009 ). In contrast, the maximum number of B. xylophilus per beetle in this study was 11,260. This difference may be because pheromone-trapped beetles are not captured immediately after emergence, but rather after feeding on healthy pine trees, potentially allowing for nematode loss before collection. The density of B. xylophilus in beetles peaks 2–3 weeks post-emergence before declining (Enda, 1972 ; Hosoda & Kobayashi, 1978 ; Kim et al., 2009 ; Mineo, 1975 ). Considering this pattern, pheromone traps should be used primarily for monitoring rather than for direct PWD control. Comparison of temperature-dependent vector distribution across the survey sites Considering that the daily average temperature varied among survey sites, a correlation analysis was performed to examine the relationship between temperature differences and the density of M. alternatus , the primary vector of PWD, at different collection dates. In addition, we examined the relationship between vector density and annual variations. A comparison of the average temperature and M. alternatus density at each site showed a significant positive correlation at all locations: Site 1 ( r = 0.786, p < 0.01), Site 2 ( r = 0.744, p < 0.01), and Site 3 ( r = 0.755, p < 0.01) (Fig. 6 ). Although correlation coefficients varied slightly among sites, all results indicated that M. alternatus emergence timing was closely associated with daily average temperatures, with higher temperatures leading to increased beetle densities. A year-on-year comparison of M. alternatus density and daily average temperature also revealed significant positive correlations for 2021 ( r = 0.717, p < 0.01), 2022 ( r = 0.751, p < 0.01), and 2023 ( r = 0.829, p < 0.01) (Fig. 7 ). Collectively, these findings suggest that the timing of emergence of M. alternatus is affected by yearly temperature fluctuations and daily average temperatures, with warm temperatures associated with earlier and higher-density emergence than cold temperatures. Conclusions Distribution of B. xylophilus and its vectors In this study, we investigated the distribution and density of PWN among dead pine trees ( Pinus densiflora and Pinus thunbergii ) across coastal and inland regions of South Korea, as well as the mortality rate of pine trees affected by PWD. In addition, the seasonal timing of Monochamus alternatus attraction to aggregation pheromone traps was examined to clarify the emergence period of vector beetles in response to climate change. A strong negative correlation was found between the densities of two nematode species in felled trees, Bursaphelenchus xylophilus and B. mucronatus , suggesting a potential competitive interaction between them. Previous studies have shown that B. mucronatus density is higher than B. xylophilus in long-dead trees (Ha & Lee, 2017 ; Park et al., 2014 ). Considering the relationship between the highly pathogenic B. xylophilus and the less pathogenic B. mucronatus , targeting recently dead trees for PWD control may be more effective than removing long-dead trees. During the three-year survey period (2021–2023), an average of 30.1 M. alternatus individuals were collected across all sites, among which 16.6 individuals (61.3%) were found to host B. xylophilus . The higher proportion of infected beetles in areas with recurring PWD outbreaks suggests that M. alternatus populations in these regions play a significant role in disease transmission. Considering that the average flight distance of M. alternatus is 8.0 km (National Institute of Forest Science, 2023 ), preventive tree injections and chemical vector control measures should be prioritized within an 8 km radius of infected forest areas, particularly during the M. alternatus emergence period. A significant positive correlation was found between daily average temperature and M. alternatus collection density across all survey sites. The first beetle collection occurred when the average temperature exceeded 20°C. In addition, the earlier the temperature increased in May, the earlier beetles were collected, suggesting that rising temperatures accelerate emergence. Considering the ongoing trend of rapid temperature increases due to climate anomalies in South Korea, continued monitoring of M. alternatus emergence timing is crucial for determining the optimal timing of control measures. Statements and Declarations Acknowledgements : None. Author contributions Chong Kyu Lee: Conceptualization, Project administration, Investigation, Supervision, Writing—review & editing, Resources, Methodology, Formal analysis Hyun Kim: Conceptualization, Methodology, Formal analysis, Writing—review & editing Man-Leung Ha: Conceptualization, Investigation, Writing—original draft, Resources, Software, Data curation, Formal analysis, Validation, Visualization, Writing—original draft Funding The authors did not receive support from any organization for the submitted work. Data availability The data that support the findings of this study are available from the corresponding author, [M-L Ha], upon reasonable request. Conflict of interest The authors declare that no known conflicts of interest exist. Ethical Approval Not applicable. References Abelleira, A., Picoaga, A., Mansilla, J. P., & Aguin, O. (2011). Detection of Bursaphelenchus xylophilus , causal agent of pine wilt disease on Pinus pinaster in northwestern Spain. Plant Disease , 95 (6), 776. https://doi.org/10.1094/PDIS-12-10-0902 Baermann, G. 1917. Eine einfache methode zur auffindung von Ancylostomum (Nematoden) larven in erdproben. Geneeskd Tijdschr Ned Indie, 57 , 131–137. Cheng, H. R., Lin, M., Li, W., & Fang, Z. (1983). The occurrence of a pine wilting disease caused by a nematode found in Nanjing. Forest Pest and Disease , 4 (1), 1–5. Dwinell, L. D., & Nickle, W. R. (1989). An overview of the pine wood nematode ban in North America . General Technical Report SE-55. USDA Forest Service. Enda, N. (1972). Removing dauer larvae of Bursaphelenchus lignicolus from the body of Monochamus alternatus . Transactions of the Annual Meeting of the Kanto Branch of the Japanese Forestry Society, 24 , 32. Enda, N. (1989). The status of pine wilt disease caused by Bursaphelenchus xylophilus (Steiner et Buhrer) Nickle and its control in Korea. Journal of Korean Society of Forest Science , 78 (2), 248–253. (in Korean) Futai, K. (2008). Pine wilt in Japan: From first incidence to the present. In B. G. Zhao, K. Futai, J. R. Sutherland, & Y. Takeuchi (Eds.). Pine wilt disease , (pp. 5–12). Tokyo, Japan: Springer. https://doi.org/10.1007/978-4-431-75655-2_2. Ha, M. L., & Lee, C. K. (2017). Study on the damage by pine wood nematode in black pine trees. Journal of Forest and Environmental Science , 33 , 105–112. Hirata, A., Nakamura, K., Nakao, K., Kominami, Y., Tanaka, N., Ohashi, H., Takano, K. T., Takeuchi, W., & Matsui, T. (2017). Potential distribution of pine wilt disease under future climate change scenarios. PLOS One , 12 (8), e0182837. https://doi.org/10.1371/journal.pone.0182837 Hosoda, R., & Kobayashi, K. (1978). Drop-off procedures of the pine wood nematode from the pine sawyer (II). Transactions of the Annual Meeting of the Kanto Branch of the Japanese Forestry Society , 29 , 131–133. Jung, J. K., Hong, E. J., Kim, T. G., & Jeong, J. C. (2018). Ground beetle (Coleoptera: Carabidae) assemblage structure in Taeanhaean national park: A comparison between coastal dune and windbreak forest. Korean Journal of Environment and Ecology , 32 (2), 147–153. https://doi.org/10.13047/KJEE.2018.32.2.147 Jung, J. K., Kwon, H. J., Kim, H., Kim, J. H., Nam, Y. W., Kim, D. S., & Jung, C. S. (2020). Changes in catch rate of Monochamus saltuarius (Coleoptera: Cerambycidae) relation to sexual maturation. Korean Journal of Applied Entomology , 59 (4), 295–301. Kim, D. S., Lee, S. M., Chung, Y. J., Choi, K. S., Moon, Y. S., & Park, C. G. (2003). Emergence ecology of Japanese pine sawyer, Monochamus alternatus (Coleoptera: Cerambycidae), a vector of pinewood nematode, Bursaphelenchus xylophilus . Korean Journal . Applied . Entomology , 42 , 307–313. Kim, D. S., Lee, S. M., Huh, H. S., Park, N. C., & Park, C. G. (2009). Escape of pine wood nematode, Bursaphelenchus xylophilus , through feeding and oviposition behavior of Monochamus alternatus and M. saltuarius (Coleoptera: Cerambycidae) adults. Korean Journal of Applied Entomology , 48 (4), 527–533. https://doi.org/10.5656/KSAE.2009.48.4.527 Kim, J., Lee, S. M., Jung, Y. H., Kwon, Y. D., Kim, D. S., Lee, D. W., & Park, C. G. (2016). Field evaluation on the synergistic attractiveness of 2-(1-undecyloxy)-1-ethanol and ipsenol to Monochamus saltuarius . Entomological Research , 46 (1), 31–35. https://doi.org/10.1111/1748-5967.12145 Kishi, Y. (1995). Pine wood nematode and the Japanese pine sawyer. Tokyo, Japan: Thomas Company Ltd . , p. 302. Knowles, K., Beaubien, Y., Wingfield, M. J., & French, D. W. (1983). The pinewood nematode new in Canada. Forestry Chronicle , 59 (1), 40. Kobayashi, F., Yamane, A., & Ikeda, T. (1984). The Japanese pine sawyer beetle as the vector of pine wilt disease. Annual Review of Entomology , 29 (1), 115–135. https://doi.org/10.1146/annurev.en.29.010184.000555 Korea Forest Service. (2023). Statistical yearbook of forestry No. 53 . Seoul, Republic of Korea: Korea Forest Service, p. 36. Korea Meteorological Administration. (2023). Climate statistics analysis . Retrieved March 26, 2024 from https://data.kma.go.kr/climate/RankState/selectRankStatisticsDivisionList.do?pgmNo=179 Kwon, T. S., Lim, J. H., Sim, S. J., Kwon, Y. D., Son, S. K., Lee, K. Y., Kim, Y. T., Park, J. W., Shin, C. H., Ryu, S. B., & Lee, C. K. (2006). Distribution patterns of Monochamus alternatus and M. saltuarius (Coleoptera: Cerambycidae) in Korea. Journal of Korean Forestry Society , 95 (5), 543. Lee, H. R., Lee, S. C., Lee, D. H., Choi, W. S., Jung, C. S., Jeon, J. H., Kim, J. E., & Park, I. K. (2017). Identification of the aggregation-sex pheromone produced by male Monochamus saltuarius , a major insect vector of the pine wood nematode. Journal of Chemical Ecology , 43 (7), 670–678. https://doi.org/10.1007/s10886-017-0864-6 Lee, M. Y., Lee, C. H., Ha, M. L., & Kim, H. (2023). The dynamics of pine wilt nematode ( Bursaphelenchus xylophilus ) in pine wilt disease infected trees on Gyeongsangnam-do, Sachun-City. The Journal of Korean Island , 35 (1), 213–227. https://doi.org/10.26840/JKI.35.1.213 Lee, S. M., Jung, Y. H., Seo, S. T., Kim, D. S., & Lee, D. W. (2021). Comparison of nematicidal effect and residual amount by injection time and number of holes using emamectin benzoate via tree injection against pine wood nematode, Bursaphelenchus xylophilus . Korean. Journal of Pesticide Sciences , 25 (4), 371–378. (in Korean) Lu, Q., Wang, W., Liang, J., Yan, D., Jia, X., & Zhang, X. (2005). Potential suitability assessment of Bursaphelenchus xylophilus in China. Forest Research Chinese Academy of Forestry, 18 (4), 460–464. Mamiya, Y. (1983). Pathology of the pine wilt disease caused by Bursaphelenchus xylophilus . Annual Review of Phytopathology , 21 (1), 201–220. https://doi.org/10.1146/annurev.py.21.090183.001221 Mamiya, Y. (1988). History of pine wilt disease in Japan. Journal of Nematology , 20 (2), 219–226. Mamiya, Y., & Enda, N. (1972). Transmission of Bursaphelenchus lignicolus (Nematoda: Aphelenchoididae) by Monochamus alternatus (Coleoptera: Cerrambycidae). Nematologica , 18 , 159–162. Mineo, K. (1975). Drop-off of pine wood nematodes from the pine sawyer and their invasion of pine trees. Transactions of the Annual Meeting of the Kanto Branch of the Japanese Forestry Society, 26 , 275–278. Mota, M. M., Braasch, H., Bravo, M. A., Penas, A. C., Burgermeister, W., Metge, K., & Sousa, E. (1999). First report of Bursaphelenchus xylophilus in Portugal and in Europe. Nematology , 1 (7), 727–734. https://doi.org/10.1163/156854199508757 Myers, R. F. (1988). Pathogenesis in pine wilt caused by pinewood nematode, Bursaphelenchus xylophilus . Journal of Nematology , 20 (2), 236–244. National Institute of Forest Science. (2023). A study on the establishment of a comprehensive management system for prevention of the spread of pine nematode damage. National Institute of Forest Science Research Report, 23 (28), 14–22. Pajares, J. A., Alvarez, G., Ibeas, F., Gallego, D., Hall, D. R., & Farman, D. I. (2010). Identification and field activity of a male-produced aggregation pheromone in the pine sawyer beetle, Monochamus galloprovincialis . Journal of Chemical Ecology , 36 (6), 570–583. https://doi.org/10.1007/s10886-010-9791-5 Park, M. H. (2013). Diversity and distribution of beetles ( Coleoptera Carabidae ) in Jangsan (Mt), Busan. M.D. Thesis, Kyeongnam National Univ. of Sci. and Tech. Jinju, p. 43. Park, S. C., Moon, Y. S., & Kim, D. S. (2014). Low-pathogenic pinewood nematode found in dead trees and resistance of pines induced by its pre-inoculation. Korean Journal of Applied Entomology , 53 (2), 141–147. https://doi.org/10.5656/KSAE..2014.03.0.013 Rutherford, T. A., & Webster, J. M. (1987). Distribution of pine wilt disease with respect to temperature in North America, Japan, and Europe. Canadian Journal of Forest Research , 17 (9), 1050–1059. https://doi.org/10.1139/x87-161 SAS Institute Inc. (2003). SAS/STAT statistical software . (version 9.1). Cary, NC: SAS Publishing. Sutherland, J. R., Ring, F. M., & Seed, J. E. (1991). Canadian conifers as hosts of the pinewood nematode ( Bursaphelenchus xylophilus ): Results of seedling inoculations. Scandinavian Journal of Forest Research , 6 (1–4), 209–216. https://doi.org/10.1080/02827589109382662 Xu, Q., Zhang, X., Li, J., Ren, J., Ren, L., & Luo, Y. (2023). Pine wilt disease in Northeast and Northwest China: A comprehensive risk review. Forests , 14 (2), 174. https://doi.org/10.3390/f14020174 Yi, C. K., Byun, B. H., Park, J. D., Yang, S. I., & Chang, K. H. (1989). First finding of the pine wood nematode. Bursaphelenchus xylophilus (Sterner et Buhrer) Nickle and its insect vector in Korea. Research Reports of the Forestry Research Institute (Seoul) , 38 , 141–149. (in Korean) Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 22 Apr, 2025 Reviewers invited by journal 14 Apr, 2025 Editor invited by journal 24 Mar, 2025 Editor assigned by journal 24 Mar, 2025 First submitted to journal 19 Mar, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6261204","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":442514047,"identity":"2608c2e4-5a8d-4e98-a1ea-22fe413c44f2","order_by":0,"name":"Chong Kyu Lee","email":"","orcid":"","institution":"Gyeongsang National University","correspondingAuthor":false,"prefix":"","firstName":"Chong","middleName":"Kyu","lastName":"Lee","suffix":""},{"id":442514048,"identity":"46c1c026-1dd0-47cb-a46e-fe4d86811880","order_by":1,"name":"Hyun Kim","email":"","orcid":"","institution":"Gyeongsang National University","correspondingAuthor":false,"prefix":"","firstName":"Hyun","middleName":"","lastName":"Kim","suffix":""},{"id":442514049,"identity":"7956beeb-3e9f-4418-a271-9236ecf64867","order_by":2,"name":"Man-Leung Ha","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA5klEQVRIiWNgGAWjYBACPjBpwCbHz94AFeIhoIUNTFbwGUv2HCBJyxm5xA03EojVwt5j9vBrm1nihpvPrz3mYbCTZ+A5+wC/Fp4z5saybWnGM2/nlBvzMCQbNvC2G+DXIpFjJi3Zdky273ZOmjQPA3MCAz8bAYfJvwFp+c/YcPMMSEs9EVokeMwkP5xhU5xwg/0YUMvhBAbeNgJaeNLKpBkq2ICBnMMmOcfguGEbzzH8WvjZD2+T/AGOyuPPJN5UVMvz86Th1wICzJCY4AEGlAEspggAxh9giv0BMYpHwSgYBaNgBAIA3io5ehtf4aAAAAAASUVORK5CYII=","orcid":"","institution":"Gyeongsang National University","correspondingAuthor":true,"prefix":"","firstName":"Man-Leung","middleName":"","lastName":"Ha","suffix":""}],"badges":[],"createdAt":"2025-03-19 11:43:08","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6261204/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6261204/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":81396679,"identity":"9898907a-4ff6-4902-af53-9f49595597e1","added_by":"auto","created_at":"2025-04-25 15:40:38","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":22505831,"visible":true,"origin":"","legend":"\u003cp\u003eSurvey areas.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;Site 1 (Geoje investigation area) – PWD damage level: “Severe”\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;Site 2 (Sacheon investigation area) – PWD damage level: “Severe”\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;Site 3 (Jinju investigation area) – PWD damage level: “Moderate”\u003c/p\u003e","description":"","filename":"Fig1.png","url":"https://assets-eu.researchsquare.com/files/rs-6261204/v1/229a01f0d093e7053f316951.png"},{"id":81394784,"identity":"21aeed39-3eaa-48a0-aebc-5f12333e34f6","added_by":"auto","created_at":"2025-04-25 15:24:38","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1255203,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eBursaphelenchus xylophilus \u003c/em\u003edensity in felled trees at the three survey sites. (Statistical differences were determined usingDuncan’s multiple range test [DMRT]. Means sharing the same letter above the bars are not significantly different [\u003cem\u003ep\u003c/em\u003e\u0026lt; 0.05])\u003cem\u003eBursaphelenchus xylophilus \u003c/em\u003edensity in felled trees at the three survey sites. (Statistical differences were determined usingDuncan’s multiple range test [DMRT]. Means sharing the same letter above the bars are not significantly different [\u003cem\u003ep\u003c/em\u003e\u0026lt; 0.05])\u003c/p\u003e","description":"","filename":"Fig2.png","url":"https://assets-eu.researchsquare.com/files/rs-6261204/v1/9509db15f920e9ce1ce11bb1.png"},{"id":81396678,"identity":"20efcebf-dff3-4549-a6ba-5f08b834ae59","added_by":"auto","created_at":"2025-04-25 15:40:38","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1221457,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eBursaphelenchus mucronatus\u003c/em\u003e density in felled trees at the three survey sites. (Statistical differences were determined usingDuncan’s multiple range test [DMRT]. Means with the same letter above the bars are not significantly different [\u003cem\u003ep\u003c/em\u003e\u0026lt; 0.05])\u003c/p\u003e","description":"","filename":"Fig3.png","url":"https://assets-eu.researchsquare.com/files/rs-6261204/v1/3a59010960b5ba5dee4fa172.png"},{"id":81395550,"identity":"a14acaca-0cf4-4cb7-ab3e-4dd995ddd0e8","added_by":"auto","created_at":"2025-04-25 15:32:38","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":4301910,"visible":true,"origin":"","legend":"\u003cp\u003eComparison of \u003cem\u003eBursaphelenchus xylophilus\u003c/em\u003e and \u003cem\u003eBursaphelenchus mucronatus\u003c/em\u003e densities in felled trees (\u003csup\u003e**\u003c/sup\u003e\u003cem\u003ep \u003c/em\u003e\u0026lt; 0.01)\u003c/p\u003e","description":"","filename":"Fig4.png","url":"https://assets-eu.researchsquare.com/files/rs-6261204/v1/430905a948b83ffc760f4d5d.png"},{"id":81394798,"identity":"7efc59b7-ef20-48e1-96c9-6d0566fd82a0","added_by":"auto","created_at":"2025-04-25 15:24:38","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":23899050,"visible":true,"origin":"","legend":"\u003cp\u003eDates of male and female \u003cem\u003eMonochamus alternatus\u003c/em\u003eemergence and densities at the three survey sites. (Statistical differences were determined using Duncan’s multiple range test [DMRT]. Means with the same letter above the bars are not significantly different [\u003cem\u003ep\u003c/em\u003e \u0026lt; 0.05])\u003c/p\u003e","description":"","filename":"Fig5.png","url":"https://assets-eu.researchsquare.com/files/rs-6261204/v1/be037d49e9c7cabc65654a49.png"},{"id":81394793,"identity":"77d01575-78c2-45b2-bec8-5235870c2440","added_by":"auto","created_at":"2025-04-25 15:24:38","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":6974220,"visible":true,"origin":"","legend":"\u003cp\u003eRelationship between \u003cem\u003eMonochamus alternatus\u003c/em\u003e adult collection dates and average temperatures at the three survey sites (**\u003cem\u003ep\u003c/em\u003e \u0026lt; 0.01)\u003c/p\u003e","description":"","filename":"Fig6.png","url":"https://assets-eu.researchsquare.com/files/rs-6261204/v1/fd65cd54a4e73f20def6c410.png"},{"id":81395554,"identity":"0456f6fb-5dcd-42d2-b0a0-02122de94ccc","added_by":"auto","created_at":"2025-04-25 15:32:38","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":6507632,"visible":true,"origin":"","legend":"\u003cp\u003eRelationship between the collection dates of \u003cem\u003eMonochamus alternatus \u003c/em\u003eadults and the average temperature on those dates during 2021–2023 (\u003csup\u003e**\u003c/sup\u003e\u003cem\u003ep\u003c/em\u003e \u0026lt; 0.01)\u003c/p\u003e","description":"","filename":"Fig7.png","url":"https://assets-eu.researchsquare.com/files/rs-6261204/v1/9d6b1e3ddaa83bc2b289cb6d.png"}],"financialInterests":"","formattedTitle":"Distribution of pine wood nematodes and their vectors","fulltext":[{"header":"Introduction","content":"\u003cp\u003ePine trees (genus \u003cem\u003ePinus\u003c/em\u003e) are the most cherished and symbolically significant trees in Korea, and are deeply rooted in their culture and history. In addition, they constitute the largest proportion of coniferous forests in the country. Pine trees play a crucial role in various ecological functions, including air purification, forest recreation, and water regulation as green dams (Korea Forest Service, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). However, global warming, the increasing frequency of large-scale wildfires, and the rapid spread of pine wilt disease (PWD) place pine trees and the entire coniferous forest ecosystem at risk.\u003c/p\u003e \u003cp\u003ePWD is caused by the pine wood nematode (PWN; \u003cem\u003eBursaphelenchus xylophilus\u003c/em\u003e), which enters the vascular system of pine trees, proliferates rapidly, and ultimately causes tree death (Kobayashi et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1984\u003c/span\u003e; Myers, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e1988\u003c/span\u003e). Although pine species are native to North America, the presumed origin of the nematode is generally PWD resistance (Dwinell \u0026amp; Nickle \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e1989\u003c/span\u003e; Knowles et al., \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e1983\u003c/span\u003e; Sutherland et al., \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e1991\u003c/span\u003e). The disease has become a global forest epidemic since its introduction in South Korea, China, Japan, Portugal, and Spain (Abelleira et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Cheng et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e1983\u003c/span\u003e; Enda, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e1989\u003c/span\u003e; Kobayashi et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1984\u003c/span\u003e; Mota et al., \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e1999\u003c/span\u003e; Xu et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Yi et al., \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e1989\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eConsidering that pine wood nematodes (PWN) cannot move on their own, they rely on insect vectors for dispersal. The nematode enters the body of its vector during its larval stage and spreads when vector beetles feed on healthy pine branches or lay eggs beneath the bark, creating entry points for infection (Dwinell \u0026amp; Nickle, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e1989\u003c/span\u003e; Mamiya \u0026amp; Enda, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e1972\u003c/span\u003e). In South Korea, the primary vectors of PWN are the Japanese pine sawyer (\u003cem\u003eMonochamus alternatus\u003c/em\u003e Hope) and northern pine sawyer (\u003cem\u003eM. saltuarius\u003c/em\u003e Gebler), which predominantly infest Pinus red pine (\u003cem\u003ePinus densiflora\u003c/em\u003e), black pine (\u003cem\u003ePinus thunbergii\u003c/em\u003e), and Korean pine (\u003cem\u003ePinus koraiensis\u003c/em\u003e) (Enda, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e1989\u003c/span\u003e; Kishi, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e1995\u003c/span\u003e; Yi et al., \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e1989\u003c/span\u003e). Therefore, the occurrence and spread of PWD are closely linked to the ecological dynamics of nematodes and their vectors.\u003c/p\u003e \u003cp\u003eThe occurrence and spread of PWD are strongly influenced by climatic and environmental factors, including the temperature, precipitation, topography, slope, and elevation of pine habitats (Futai, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; Park et al., 2013). Temperature plays a crucial role in PWD outbreaks and expansion as it significantly affects the growth, development, and distribution of both PWN and its insect vectors (Futai, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; Hirata et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Lu et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2005\u003c/span\u003e). Studies in North America and Japan have shown that PWD occurs in regions where the average annual temperature exceeds 20\u0026deg;C (Rutherford \u0026amp; Webster, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e1987\u003c/span\u003e). In South Korea, the northern and southern distribution limits of \u003cem\u003eM. alternatus\u003c/em\u003e correspond to annual mean temperatures of approximately 10\u0026deg;C and 13.2\u0026deg;C, respectively (Kwon et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2006\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eTo mitigate PWD damage, it is essential to monitor and control the populations of the vector beetles \u003cem\u003eM. alternatus\u003c/em\u003e and \u003cem\u003eM. saltuarius\u003c/em\u003e (Jung et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Field surveys, which include monitoring oviposition sites and deploying aggregation pheromone traps, are widely used to track vector activity and population dynamics. These methods help determine the optimal timing for insecticide application and the removal of infected trees, which are crucial steps in controlling PWD outbreaks (Jung et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eTo date, little research has been conducted in Korea on the timing of PWN and vector distributions in relation to abnormal high-temperature events and rising average temperatures caused by global warming. To minimize PWD damage to pine trees, it is essential to analyze the factors influencing its occurrence and spread, identify optimal prevention and control periods and high-risk regions, and implement coordinated measures to prevent further outbreaks and expansion.\u003c/p\u003e \u003cp\u003eTo achieve this goal, we examined the distribution and density of PWN in dead pine trees across coastal and inland regions as well as the mortality rates of infected trees. In addition, we investigated the seasonal emergence patterns of \u003cem\u003eM. alternatus\u003c/em\u003e adults by analyzing their attraction to aggregation pheromone traps to determine the climate-driven variations in vector emergence timing.\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eSelection of survey sites\u003c/h2\u003e \u003cp\u003eSurvey sites were selected in areas that experienced moderate to severe PWD damage each year. Coastal sites were chosen from forested regions dominated by black pine trees in Jangseungpo-dong, Ilun-myeon, Geoje-si, Seopo-myeon, and Sacheon-si. Inland sites were selected in forested areas with recurring PWD in Jangjae-dong, Hachon-dong, and Jinju-si (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). This survey was conducted between 2021 and 2023.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eGeographical coordinates and pine wilt disease (PWD) damage levels at the survey sites.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSite\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eArea\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLocation (GPS)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePWD damage level\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSite 1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGeoje-si,\u003c/p\u003e \u003cp\u003eJangseungpo-dong,\u003c/p\u003e \u003cp\u003eIrun-myeon\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e34\u0026deg; 84` 50\" N\u003c/p\u003e \u003cp\u003e128\u0026deg; 73\u0026rsquo; 02\" E\u003c/p\u003e \u003cp\u003e34\u0026deg; 82\u0026rsquo; 53\" N\u003c/p\u003e \u003cp\u003e128\u0026deg; 71\u0026rsquo; 56\" E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSevere\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSite 2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSacheon-si,\u003c/p\u003e \u003cp\u003eSeopo-myeon\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e34\u0026deg; 99\u0026rsquo; 34\" N\u003c/p\u003e \u003cp\u003e127\u0026deg; 94\u0026rsquo; 51\" E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSevere\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSite 3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eJinju-si,\u003c/p\u003e \u003cp\u003eJangjae-dong,\u003c/p\u003e \u003cp\u003eHachon-dong\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e35\u0026deg; 20\u0026rsquo; 36\" N\u003c/p\u003e \u003cp\u003e128\u0026deg; 10\u0026rsquo; 00\" E\u003c/p\u003e \u003cp\u003e35\u0026deg; 21\u0026rsquo; 98\" N\u003c/p\u003e \u003cp\u003e128\u0026deg; 07\u0026rsquo; 47\" E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eModerate\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eSelection of tree species for investigation at each site\u003c/h3\u003e\n\u003cp\u003eThree survey plots measuring 20 \u0026times; 20 m each were established in areas with severe PWD outbreaks. Five dead black pine trees ranging in age from 20 to 40 years were randomly selected from each plot for sampling. The distribution areas were located at elevations ranging from 50 to 200 m. Tree heights ranged from 8 to 14 m, with the diameter at breast height (DBH) varying between 20 and 34 cm.\u003c/p\u003e\n\u003ch3\u003eDistribution of PWN and B. mucronatus in felled trees\u003c/h3\u003e\n\u003cp\u003eAmong the trees that had been felled to control PWD, dead trees were selected for sampling. Following the PWD Control Guidelines (Korea Forest Service, 2016), wood samples were collected from three sections of the tree to assess PWN density in felled trees: the upper canopy (stem and branches at the tree crown), middle canopy (stem in the middle portion of the crown), and lower trunk (stem at breast height). Sampling was conducted from February to March each year from 2021 to 2023 during felling operations for PWD control. The collected samples were processed in the laboratory using the Baermann funnel method (Baermann, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e1917\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eWood samples were finely chopped (\u0026lt;\u0026thinsp;5 mm), and 20 mL of the extract was obtained from the solution collected at the bottom after 24 h. Thereafter, 10 \u0026micro;L of each extract was placed on a glass slide and observed under a stereomicroscope (Olympus SZ61, Tokyo, Japan) at \u0026times;10\u0026ndash;\u0026times;20 magnification. Three replications were conducted for each wood sample to quantify the number of PWN and \u003cem\u003eB. mucronatus\u003c/em\u003e. The densities of PWN and \u003cem\u003eB. mucronatus\u003c/em\u003e measured throughout the study period were analyzed and compared.\u003c/p\u003e\n\u003ch3\u003eMonitoring the emergence of M. alternatus using aggregation pheromone traps\u003c/h3\u003e\n\u003cp\u003eSurveys were conducted using aggregation pheromone traps to investigate the emergence period of \u003cem\u003eM\u003c/em\u003e. \u003cem\u003ealternatus\u003c/em\u003e, the primary vector of PWN. Survey sites were selected in three cities that are heavily affected by PWD: Geoje, Sacheon, and Jinju. At each site, 20 \u0026times; 20 m plots were established in areas containing dead pine trees, and trees with \u003cem\u003eM. alternatus\u003c/em\u003e emergence holes were selected as sample trees.\u003c/p\u003e \u003cp\u003eAt each site, three multiple-funnel traps (KN, Iksan, Korea) were installed around dead and weakened trees within a 3 m radius, with 4 m spacing between traps. Each trap was baited with 2-(undecyloxy)ethanol, α-pinene, ethanol (EtOH) and an attractant. The survey was conducted biweekly from early May to late June of each year from 2021 to 2023, corresponding to the expected emergence period of \u003cem\u003eM. alternatus\u003c/em\u003e.\u003c/p\u003e \u003cp\u003eTo analyze the effect of temperature on vector emergence time, daily average temperature data (Korea Meteorological Administration, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) for each survey site were obtained on eight dates in May and June at weekly intervals. Temperature data were analyzed in relation to the number of collected vectors (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDaily average temperature (\u0026deg;C) recorded at each survey site on collection dates (2021\u0026ndash;2023)\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"11\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eArea\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eYear\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"9\" nameend=\"c11\" namest=\"c3\"\u003e \u003cp\u003eMonth/Day\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5/6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003e5/13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e5/19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e5/27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e6/2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e6/10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e6/17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e6/24\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eSite 1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2021\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e18.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e19.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e20.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e17.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e21.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e23.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e20.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e21.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2022\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e19.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e18.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e19.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e22.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e20.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e20.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e22.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e23.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2023\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e15.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e17.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e18.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e22.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e22.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e22.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e23.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e22.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eSite 2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2021\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e17.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e20.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e20.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e19.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e21.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e22.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e21.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e21.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2022\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e20.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e19.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e20.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e22.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e21.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e20.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e22.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e24.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2023\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e16.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e18.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e20.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e21.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e23.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e22.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e23.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e22.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eSite 3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2021\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e13.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e21.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e20.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e17.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e20.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e22.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e21.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e21.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2022\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e19.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e20.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e19.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e21.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e21.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e20.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e22.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e25.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2023\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e16.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e16.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e20.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e21.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e22.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e22.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e23.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e23.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e\n\u003ch3\u003eInvestigation of PWN presence in M. alternatus\u003c/h3\u003e\n\u003cp\u003eTo investigate the presence of PWN within their vector insects, beetles collected from pheromone traps were brought to the laboratory for examination. After determining the sex of each beetle, their surfaces were rinsed with distilled water before dissection. Thereafter, nematodes within the beetles were isolated using the Baermann funnel method. This process was conducted in triplicate and the number of PWN was quantified.\u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eData analysis\u003c/h2\u003e \u003cp\u003eAll survey results were analyzed using one-way analysis of variance (ANOVA), followed by Duncan\u0026rsquo;s multiple range test for post hoc comparisons. In addition, correlations between survey results and average temperatures across years, months, and days at each survey site were analyzed (SAS Institute Inc., 2003). Statistical significance was set at 5% (α\u0026thinsp;=\u0026thinsp;0.05) and all statistical analyses were performed using SAS Ver. 9.1.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results and discussion","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003ePWN density in felled black pine trees\u003c/h2\u003e \u003cp\u003eAt each survey site, PWN density was measured in three sections of recently dead trees: the upper canopy, the middle canopy, and the lower trunk.\u003c/p\u003e \u003cp\u003eIn 2021, the highest PWN density was recorded in the middle canopy at Sites 1 (n\u0026thinsp;=\u0026thinsp;679.4/g) and 2 (n\u0026thinsp;=\u0026thinsp;601.3/g). In contrast, the highest density was recorded in the lower trunk of Site 3 (n\u0026thinsp;=\u0026thinsp;564.9/g). As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, the lowest PWN density was recorded in the lower trunk at Site 1 (n\u0026thinsp;=\u0026thinsp;585.9/g), upper canopy at Site 2 (n\u0026thinsp;=\u0026thinsp;567.3/g), and middle canopy at Site 3 (n\u0026thinsp;=\u0026thinsp;430.5/g) (Site 1: F\u0026thinsp;=\u0026thinsp;8,282.03, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001; Site 2: F\u0026thinsp;=\u0026thinsp;325.71, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001; Site 3: F\u0026thinsp;=\u0026thinsp;1,807.13, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn 2022, the highest PWN density was recorded in the lower trunk at Site 1 (n\u0026thinsp;=\u0026thinsp;521.1/g), upper canopy at Site 2 (n\u0026thinsp;=\u0026thinsp;672.2/g), and middle canopy at Site 3 (n\u0026thinsp;=\u0026thinsp;617.1/g). As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, the lowest PWN density was recorded in the middle canopy at Site 1 (n\u0026thinsp;=\u0026thinsp;461.6/g), lower trunk at Site 2 (n\u0026thinsp;=\u0026thinsp;600.9/g), and upper canopy at Site 3 (n\u0026thinsp;=\u0026thinsp;574.0/g) (Site 1: F\u0026thinsp;=\u0026thinsp;2,204.33, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001; Site 2: F\u0026thinsp;=\u0026thinsp;1,589.18, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001; Site 3: F\u0026thinsp;=\u0026thinsp;11,859.2, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001).\u003c/p\u003e \u003cp\u003eIn 2023, the highest PWN density was recorded in the lower trunk at Site 1 (n\u0026thinsp;=\u0026thinsp;624.7/g), middle canopy at Site 2 (n\u0026thinsp;=\u0026thinsp;733.7/g), and upper canopy at Site 3 (n\u0026thinsp;=\u0026thinsp;713.4/g). As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, the lowest PWN density was recorded in the upper canopy at Site 1 (n\u0026thinsp;=\u0026thinsp;624.7/g), lower trunk at Site 2 (n\u0026thinsp;=\u0026thinsp;688.9/g), and lower trunk at Site 3 (n\u0026thinsp;=\u0026thinsp;681.0/g) (Site 1: F\u0026thinsp;=\u0026thinsp;1,531.38, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001; Site 2: F\u0026thinsp;=\u0026thinsp;5,050.72, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001; Site 3: F\u0026thinsp;=\u0026thinsp;771.38, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001).\u003c/p\u003e \u003cp\u003eThe PWN density in felled trees did not exhibit a consistent pattern of higher densities in any specific section of the tree. Instead, density varied with the time elapsed since tree death, consistent with previous research indicating that PWN density fluctuates based on moisture content and the tree decay stage (Lee et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Mamiya, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e1983\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e1988\u003c/span\u003e). Long-dead trees have a lower moisture content, thus offering a less favorable environment for PWN survival. During tree felling for PWD control, prioritizing recently dead trees over long-dead trees may be a more effective strategy for PWD management.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eDistribution of B. mucronatus in felled trees\u003c/h2\u003e \u003cp\u003eTo investigate the distribution of \u003cem\u003eB. mucronatus\u003c/em\u003e, a nematode species closely related to PWN, sampling was performed on three sections (the upper canopy, middle canopy, and lower trunk) of recently dead trees among those felled for PWD control at each survey site.\u003c/p\u003e \u003cp\u003eIn 2021, the highest \u003cem\u003eB. mucronatus\u003c/em\u003e density was recorded in the middle canopy at Site 1 (n\u0026thinsp;=\u0026thinsp;261.7/g), whereas the lowest density was recorded in the lower trunk (n\u0026thinsp;=\u0026thinsp;235.7/g). The highest density was recorded at Sites 2 and 3 in the lower trunk (n\u0026thinsp;=\u0026thinsp;310.7/g and 413.3/g, respectively). As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, the lowest density was recorded in the middle canopy at Sites 2 (n\u0026thinsp;=\u0026thinsp;225.4/g) and 3 (n\u0026thinsp;=\u0026thinsp;384/g) (Site 1: F\u0026thinsp;=\u0026thinsp;11.646, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.009; Site 2: F\u0026thinsp;=\u0026thinsp;471.92, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001; Site 3: F\u0026thinsp;=\u0026thinsp;27.06, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn 2022, the highest \u003cem\u003eB. mucronatus\u003c/em\u003e density was recorded in the middle canopy at Site 1 (n\u0026thinsp;=\u0026thinsp;414.0/g) and Site 2 (n\u0026thinsp;=\u0026thinsp;211.4/g), and in the upper canopy at Site 3 (n\u0026thinsp;=\u0026thinsp;287.4/g). As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, the lowest density was recorded in the lower trunk at Site 1 (n\u0026thinsp;=\u0026thinsp;361.7/g) and Site 3 (n\u0026thinsp;=\u0026thinsp;225.0/g), and in the upper canopy at Site 2 (n\u0026thinsp;=\u0026thinsp;183.0/g) (Site 1: F\u0026thinsp;=\u0026thinsp;87.54, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001; Site 2: F\u0026thinsp;=\u0026thinsp;43.90, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.003; Site 3: F\u0026thinsp;=\u0026thinsp;2.887, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.132).\u003c/p\u003e \u003cp\u003eIn 2023, the highest \u003cem\u003eB. mucronatus\u003c/em\u003e density was observed in the lower trunk at Site 1 (n\u0026thinsp;=\u0026thinsp;305.7/g), and in the middle canopy at Sites 2 and 3 (n\u0026thinsp;=\u0026thinsp;227.0/g and n\u0026thinsp;=\u0026thinsp;267.7/g, respectively). As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, the lowest density was observed in the upper canopy at Site 1 (n\u0026thinsp;=\u0026thinsp;132.0/g) and in the lower trunk at Site 2 (n\u0026thinsp;=\u0026thinsp;191.4/g) and Site 3 (n\u0026thinsp;=\u0026thinsp;225.0/g) (Site 1: F\u0026thinsp;=\u0026thinsp;357.23, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001; Site 2: F\u0026thinsp;=\u0026thinsp;21.35, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.002; Site 3: F\u0026thinsp;=\u0026thinsp;51.18, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.002).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eComparison of PWN and B. mucronatus densities in felled trees\u003c/h2\u003e \u003cp\u003eA comparative analysis of \u003cem\u003eB. xylophilus\u003c/em\u003e (PWN) and \u003cem\u003eB. mucronatus\u003c/em\u003e densities in felled trees during the entire survey period revealed a strong negative correlation (\u003cem\u003er =\u003c/em\u003e ˗0.728, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01), indicating that \u003cem\u003eB. mucronatus\u003c/em\u003e density decreased with increasing distribution of \u003cem\u003eB. xylophilus\u003c/em\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). These results suggest a potentially competitive interaction between the two species. \u003cem\u003eB. xylophilus\u003c/em\u003e may outcompete \u003cem\u003eB. mucronatus\u003c/em\u003e in newly infected trees, whereas \u003cem\u003eB. mucronatus\u003c/em\u003e, a saprophytic nematode, may persist in later-stage decomposition when the conditions become less favorable for \u003cem\u003eB. xylophilus\u003c/em\u003e. Similarly, Park et al. (\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2014\u003c/span\u003e) reported that nematodes isolated from trees that died within 3 months of PWD, as well as from trees showing disease progression, were all highly virulent, whereas those from felled trees 2\u0026ndash;3 years post-mortem exhibited lower virulence.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eDensity of M. alternatus, the PWN vector\u003c/h2\u003e \u003cp\u003eTo investigate the distribution and density of \u003cem\u003eM. alternatus\u003c/em\u003e, the primary vector of PWN, pheromone trap surveys were conducted at each site during the emergence period in May and June 2021\u0026ndash;2023. 35, 39, and 35 females were collected across the three survey sites in 2021, 2022, and 2023, respectively, and 47, 55, and 50 males were captured, respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn 2021, the first collection date was May 13 at all three sites. On this date, one female, one female and two males at Site 2, and one female were collected at Site 1, Site 2, and Site 3, respectively. The peak collection date was June 10, when the highest number of individuals was recorded at all sites. Specifically, three females and seven males were captured at Site 1, four females and seven males at Site 2, and three females and five males at Site 3 (Female: F\u0026thinsp;=\u0026thinsp;9.36, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001; Male: F\u0026thinsp;=\u0026thinsp;19.87, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001).\u003c/p\u003e \u003cp\u003eIn 2022, the first collection date was May 6 at all sites. On this date, one female was collected from Site 1, one female and one male from Site 2, and one female from Site 3. The peak collection date was May 27 for Sites 1 and 2, with three females and five males at Site 1, and three females and four males at Site 2. At Site 3, the highest numbers were collected on June 3 and June 17, with two females and four males recorded on both dates (Female: F\u0026thinsp;=\u0026thinsp;2.21, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.089; Male: F\u0026thinsp;=\u0026thinsp;6.99, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.006).\u003c/p\u003e \u003cp\u003eIn 2023, the first collection date was May 20 at all the three sites. One male was collected at Site 1, two females at Site 2, and two males at Site 3. The peak collection dates varied by site: June 17 for Site 1 (four females and five males), June 3 for Site 2 (four females and five males), and June 10 for Site 3 (three females and four males) (Female: F\u0026thinsp;=\u0026thinsp;10.27, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001; Male: F\u0026thinsp;=\u0026thinsp;6.76, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.008).\u003c/p\u003e \u003cp\u003eThe emergence timing of \u003cem\u003eM. alternatus\u003c/em\u003e varied based on the average temperature, supporting previous findings that rising annual average temperatures lead to earlier emergence (Kim et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2003\u003c/span\u003e). In addition, the variation in the first collection dates across the study years and sites was ascribed to temperature differences between the survey regions. Site 1, which experiences a marine climate, had lower average temperatures in April and May than the inland Site 3. This is attributable to cooler spring sea temperatures and frequent sea fog, which result in lower average temperatures in coastal areas. Consequently, emergence at Site 1 was delayed compared to that at Site 3.\u003c/p\u003e \u003cp\u003eAcross all survey sites, males were collected more frequently than females were. However, previous studies using pheromone traps have reported almost equal male-to-female ratios in \u003cem\u003eM. alternatus\u003c/em\u003e (Lee et al., \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Pajares et al., \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). In contrast, studies on \u003cem\u003eM. saltuarius\u003c/em\u003e, another PWN vector, have shown either no sex-dependent differences in attraction (Kim et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2016\u003c/span\u003e) or even female predominance, with females being collected 2.54 times more frequently as males (Lee et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). These discrepancies suggest that environmental factors may play a role in these differences (Jung et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe pheromone trap used in this study was a commercially available product, whereas previous studies used traps with different pheromone compositions and concentrations, which may account for the variation in the male-to-female collection ratios. In addition, some studies conducted controlled experiments in artificial rearing facilities rather than field conditions, which could also explain the discrepancies. Further field research in the affected forest areas is necessary to reduce the potential confusion arising from these differences.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003eDensity of PWN hosted by M. alternatus\u003c/h2\u003e \u003cp\u003eThe number of \u003cem\u003eM. alternatus\u003c/em\u003e beetles hosting \u003cem\u003eB. xylophilus\u003c/em\u003e was examined based on the sex and collection date. In 2021, 29, 28, and 25 beetles were collected at Sites 1, 2, and 3, respectively, among which 17, 16, and 13 individuals, respectively, were found to host \u003cem\u003eB. xylophilus\u003c/em\u003e. In addition, the mean numbers of \u003cem\u003eB. xylophilus\u003c/em\u003e hosted per female and male at Site 1 were 2,083.6 (range: 380\u0026ndash;5,780) and 3,041.9 (range: 187\u0026ndash;7,354), respectively. At Site 2, the mean numbers of \u003cem\u003eB. xylophilus\u003c/em\u003e hosted by female and male \u003cem\u003eM. alternatus\u003c/em\u003e were 2,902.9 (range: 450\u0026ndash;7,247) and 2,741.6 (range: 784\u0026ndash;7,869), respectively. At Site 3, the mean numbers of \u003cem\u003eB. xylophilus\u003c/em\u003e hosted by female and male \u003cem\u003eM. alternatus\u003c/em\u003e were 5,804.4 (range: 587\u0026ndash;9,744) and 4,014.4 (range: 254\u0026ndash;8,757), respectively (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDates of \u003cem\u003eMonochamus alternatus\u003c/em\u003e emergence and the number of \u003cem\u003eBursaphelenchus xylophilus\u003c/em\u003e hosted by male and female \u003cem\u003eM\u003c/em\u003e. \u003cem\u003ealternatus\u003c/em\u003e in 2021\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" morerows=\"2\" nameend=\"c2\" namest=\"c1\" rowspan=\"3\"\u003e \u003cp\u003eDate\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003eSite 1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003eSite 2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c8\" namest=\"c7\"\u003e \u003cp\u003eSite 3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003csup\u003ez\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(n)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003csup\u003ez\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(n)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c8\" namest=\"c7\"\u003e \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003csup\u003ez\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(n)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003eMay\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5776.3\u0026thinsp;\u0026plusmn;\u0026thinsp;4.7\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3870.7\u0026thinsp;\u0026plusmn;\u0026thinsp;4.5\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3097.3\u0026thinsp;\u0026plusmn;\u0026thinsp;8.1\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2575.3\u0026thinsp;\u0026plusmn;\u0026thinsp;4.5\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4540.7\u0026thinsp;\u0026plusmn;\u0026thinsp;9.0\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4229.3\u0026thinsp;\u0026plusmn;\u0026thinsp;1583.3\u003csup\u003eab\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e5864.7\u0026thinsp;\u0026plusmn;\u0026thinsp;12.9\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e8756.0\u0026thinsp;\u0026plusmn;\u0026thinsp;4.6\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1781.7\u0026thinsp;\u0026plusmn;\u0026thinsp;10.2\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7243.7\u0026thinsp;\u0026plusmn;\u0026thinsp;3.5c\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003eJune\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1576.3\u0026thinsp;\u0026plusmn;\u0026thinsp;1312.3\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4072.2\u0026thinsp;\u0026plusmn;\u0026thinsp;3594.0\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e720.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.6\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2580.0\u0026thinsp;\u0026plusmn;\u0026thinsp;1120.0\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e580.7\u0026thinsp;\u0026plusmn;\u0026thinsp;5.7\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e2603.8\u0026thinsp;\u0026plusmn;\u0026thinsp;2103.8\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(3)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e350.4\u0026thinsp;\u0026plusmn;\u0026thinsp;286.3\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3497.0\u0026thinsp;\u0026plusmn;\u0026thinsp;2278.3\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1723.7\u0026thinsp;\u0026plusmn;\u0026thinsp;1144.4\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3200.4\u0026thinsp;\u0026plusmn;\u0026thinsp;2844.7\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e9743.0\u0026thinsp;\u0026plusmn;\u0026thinsp;2.6\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e2767.4\u0026thinsp;\u0026plusmn;\u0026thinsp;2245.4\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(3)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1472.7\u0026thinsp;\u0026plusmn;\u0026thinsp;4.6\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e566.0\u0026thinsp;\u0026plusmn;\u0026thinsp;3.6\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e454.0\u0026thinsp;\u0026plusmn;\u0026thinsp;3.6\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2062.7\u0026thinsp;\u0026plusmn;\u0026thinsp;2.5\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e7722.0\u0026thinsp;\u0026plusmn;\u0026thinsp;3465.0\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e7237.3\u0026thinsp;\u0026plusmn;\u0026thinsp;5.5\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1819.4\u0026thinsp;\u0026plusmn;\u0026thinsp;1790.3\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e780.3\u0026thinsp;\u0026plusmn;\u0026thinsp;3.5\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"8\"\u003e\u003csup\u003ez\u003c/sup\u003e Duncan\u0026rsquo;s multiple range test (DMRT). Means with the same letter within a column are not significantly different (\u003cem\u003ep\u0026thinsp;\u0026lt;\u003c/em\u003e\u0026thinsp;0.05)\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eIn 2022, 32, 32, and 30 beetles were collected at Sites 1, 2, and 3, respectively, among which 20, 15, and 18 individuals, respectively, were found to host \u003cem\u003eB. xylophilus\u003c/em\u003e. The mean number of nematodes hosted per female and male \u003cem\u003eM. alternatus\u003c/em\u003e at Site 1 was 3,504.4 (range: 240\u0026ndash;9,210) and 2,754.3 (range: 421\u0026ndash;6,350), respectively. In addition, the mean numbers of nematodes hosted per female and male \u003cem\u003eM. alternatus\u003c/em\u003e at Site 2 were 4,629.7 (range: 2,125\u0026ndash;8,570) and 3,422.8 (range: 769\u0026ndash;7,420), respectively. At Site 3, female and male \u003cem\u003eM. alternatus\u003c/em\u003e hosted 3,589.7 (range: 240\u0026ndash;7,890) and 4,100.0 (range: 547\u0026ndash;9,880) nematodes, respectively (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDates of \u003cem\u003eMonochamus alternatus\u003c/em\u003e emergence and the number of \u003cem\u003eBursaphelenchus xylophilus\u003c/em\u003e hosted by male and female \u003cem\u003eM\u003c/em\u003e. \u003cem\u003ealternatus\u003c/em\u003e in 2022\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" morerows=\"2\" nameend=\"c2\" namest=\"c1\" rowspan=\"3\"\u003e \u003cp\u003eDate\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003eSite1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003eSite2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c8\" namest=\"c7\"\u003e \u003cp\u003eSite3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003csup\u003ez\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(n)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003csup\u003ez\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(n)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c8\" namest=\"c7\"\u003e \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003csup\u003ez\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(n)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003eMay\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4749.7\u0026thinsp;\u0026plusmn;\u0026thinsp;4.5\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4007.7\u0026thinsp;\u0026plusmn;\u0026thinsp;0.6\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e5604.0\u0026thinsp;\u0026plusmn;\u0026thinsp;3.6\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3581.0\u0026thinsp;\u0026plusmn;\u0026thinsp;5.7\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2124.7\u0026thinsp;\u0026plusmn;\u0026thinsp;4.5\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e242.4\u0026thinsp;\u0026plusmn;\u0026thinsp;3.2\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e2779.7\u0026thinsp;\u0026plusmn;\u0026thinsp;6.5\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2994.0\u0026thinsp;\u0026plusmn;\u0026thinsp;2641.9\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7670.7\u0026thinsp;\u0026plusmn;\u0026thinsp;1558.6\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e9557.3\u0026thinsp;\u0026plusmn;\u0026thinsp;6.4\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2171.2\u0026thinsp;\u0026plusmn;\u0026thinsp;193.0\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3560.5\u0026thinsp;\u0026plusmn;\u0026thinsp;3063.4\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4854.7\u0026thinsp;\u0026plusmn;\u0026thinsp;2.3\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e5332.3\u0026thinsp;\u0026plusmn;\u0026thinsp;2290.2\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e4298.5\u0026thinsp;\u0026plusmn;\u0026thinsp;3936.8\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e3254.3\u0026thinsp;\u0026plusmn;\u0026thinsp;3.8\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003eJune\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5122.0\u0026thinsp;\u0026plusmn;\u0026thinsp;2.6\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2193.8\u0026thinsp;\u0026plusmn;\u0026thinsp;1159.5\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3279.7\u0026thinsp;\u0026plusmn;\u0026thinsp;433.1\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e6565.7\u0026thinsp;\u0026plusmn;\u0026thinsp;4.2b\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3764.3\u0026thinsp;\u0026plusmn;\u0026thinsp;4.0\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e7553.2\u0026thinsp;\u0026plusmn;\u0026thinsp;3610.5\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9214.3\u0026thinsp;\u0026plusmn;\u0026thinsp;4.0\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2264.3\u0026thinsp;\u0026plusmn;\u0026thinsp;5.1\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2992.3\u0026thinsp;\u0026plusmn;\u0026thinsp;4.0\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e4320.3\u0026thinsp;\u0026plusmn;\u0026thinsp;704.4\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1711.3\u0026thinsp;\u0026plusmn;\u0026thinsp;3.5\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1491.8\u0026thinsp;\u0026plusmn;\u0026thinsp;1171.9\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1618.2\u0026thinsp;\u0026plusmn;\u0026thinsp;182.1\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e905.3\u0026thinsp;\u0026plusmn;\u0026thinsp;2.9\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e3432.0\u0026thinsp;\u0026plusmn;\u0026thinsp;1808.9\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1959.8\u0026thinsp;\u0026plusmn;\u0026thinsp;1890.9\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3600.0\u0026thinsp;\u0026plusmn;\u0026thinsp;2112.8\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e5664.3\u0026thinsp;\u0026plusmn;\u0026thinsp;6.0\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1668.2\u0026thinsp;\u0026plusmn;\u0026thinsp;990.5\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e4563.3\u0026thinsp;\u0026plusmn;\u0026thinsp;4.2\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e837.0\u0026thinsp;\u0026plusmn;\u0026thinsp;320.3\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003csup\u003ez\u003c/sup\u003e Duncan\u0026rsquo;s multiple range test (DMRT). Means with the same letter within a column are not significantly different (\u003cem\u003ep\u0026thinsp;\u0026lt;\u003c/em\u003e\u0026thinsp;0.05).\u003c/p\u003e \u003cp\u003eIn 2023, 32, 29, and 24 beetles were collected at Sites 1, 2, and 3, respectively, among which 20, 16, and 14 individuals, respectively, were found to host \u003cem\u003eB. xylophilus\u003c/em\u003e. At Site 1, female and male \u003cem\u003eM. alternatus\u003c/em\u003e hosted 2,646.1 (range: 240\u0026ndash;8,080) and 2,576.6 (range: 185\u0026ndash;7,160) nematodes, respectively. In addition, female and male \u003cem\u003eM. alternatus\u003c/em\u003e hosted 2,949.4 (range: 919\u0026ndash;6,280) and 2,797.6 (range: 210\u0026ndash;8,870) nematodes, respectively, at Site 2. At Site 3, female \u003cem\u003eM. alternatus\u003c/em\u003e hosted an average of 1,226.3 nematodes (range: 80\u0026ndash;2,950), and male \u003cem\u003eM. alternatus\u003c/em\u003e hosted an average of 4,554.3 nematodes (range: 120\u0026ndash;11,260) (Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDates of \u003cem\u003eMonochamus alternatus\u003c/em\u003e emergence and the number of \u003cem\u003eBursaphelenchus xylophilus\u003c/em\u003e hosted by male and female \u003cem\u003eM\u003c/em\u003e. \u003cem\u003ealternatus\u003c/em\u003e in 2023\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" morerows=\"2\" nameend=\"c2\" namest=\"c1\" rowspan=\"3\"\u003e \u003cp\u003eDate\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003eSite1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003eSite2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c8\" namest=\"c7\"\u003e \u003cp\u003eSite3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003csup\u003ez\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(n)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003csup\u003ez\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(n)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c8\" namest=\"c7\"\u003e \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003csup\u003ez\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(n)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003eMay\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2234.7\u0026thinsp;\u0026plusmn;\u0026thinsp;1.5\u003csup\u003eab\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4359.5\u0026thinsp;\u0026plusmn;\u0026thinsp;2101.2\u003csup\u003eb\u003c/sup\u003e (2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e7430.3\u0026thinsp;\u0026plusmn;\u0026thinsp;4175.1\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5565.7\u0026thinsp;\u0026plusmn;\u0026thinsp;6.0\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1914.0\u0026thinsp;\u0026plusmn;\u0026thinsp;1898.8\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2772.0\u0026thinsp;\u0026plusmn;\u0026thinsp;2.6\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8865.3\u0026thinsp;\u0026plusmn;\u0026thinsp;4.5\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2948.3\u0026thinsp;\u0026plusmn;\u0026thinsp;2.9\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e3146.7\u0026thinsp;\u0026plusmn;\u0026thinsp;3313.0\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003eJune\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1129.7\u0026thinsp;\u0026plusmn;\u0026thinsp;352.4\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4632.3\u0026thinsp;\u0026plusmn;\u0026thinsp;2742.3\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2238.2\u0026thinsp;\u0026plusmn;\u0026thinsp;1449.8\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2586.3\u0026thinsp;\u0026plusmn;\u0026thinsp;2445.7\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e864.0\u0026thinsp;\u0026plusmn;\u0026thinsp;3.6\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e2814.3\u0026thinsp;\u0026plusmn;\u0026thinsp;299.8\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7838.8\u0026thinsp;\u0026plusmn;\u0026thinsp;467.9\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1469.2\u0026thinsp;\u0026plusmn;\u0026thinsp;2063.0\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3483.0\u0026thinsp;\u0026plusmn;\u0026thinsp;7.5\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2670.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.6\u003csup\u003eab\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e658.0\u0026thinsp;\u0026plusmn;\u0026thinsp;334.5\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e5077.3\u0026thinsp;\u0026plusmn;\u0026thinsp;15.0\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2372.0\u0026thinsp;\u0026plusmn;\u0026thinsp;2101.2\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3508.3\u0026thinsp;\u0026plusmn;\u0026thinsp;2841.7\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1158.7\u0026thinsp;\u0026plusmn;\u0026thinsp;33.5\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1595.0\u0026thinsp;\u0026plusmn;\u0026thinsp;900.5\u003csup\u003eab\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1466.8\u0026thinsp;\u0026plusmn;\u0026thinsp;1518.8\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1053.5\u0026thinsp;\u0026plusmn;\u0026thinsp;891.9\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2554.0\u0026thinsp;\u0026plusmn;\u0026thinsp;18.5\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1342.7\u0026thinsp;\u0026plusmn;\u0026thinsp;735.8\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e526.7\u0026thinsp;\u0026plusmn;\u0026thinsp;6.1\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e(0)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003csup\u003ez\u003c/sup\u003e Duncan\u0026rsquo;s multiple range test (DMRT). Means with the same letters within a column are not significantly different (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\u003c/p\u003e \u003cp\u003eThe average proportion of \u003cem\u003eM. alternatus\u003c/em\u003e individuals harboring \u003cem\u003eB. xylophilus\u003c/em\u003e across all sites was 57%, which was significantly higher than that reported in a previous nationwide survey using pheromone traps (National Institute of Forest Science, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). This discrepancy is likely due to differences in sampling methods: randomly selected pine forests versus PWD-affected pine forests. Previous research has shown that the density of \u003cem\u003eB. xylophilus\u003c/em\u003e hosted by \u003cem\u003eM\u003c/em\u003e. \u003cem\u003ealternatus\u003c/em\u003e varies by region, with a maximum of 298,000 nematodes per beetle (Kishi, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e1995\u003c/span\u003e). In addition, the proportion of beetles that emerged from \u003cem\u003eB. xylophilus\u003c/em\u003e-infested pine trees harboring \u003cem\u003eB. xylophilus\u003c/em\u003e was 38.3%, with an average of 20,083.1 nematodes per beetle (range: 56\u0026ndash;128,700) (Kim et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). In contrast, the maximum number of \u003cem\u003eB. xylophilus\u003c/em\u003e per beetle in this study was 11,260. This difference may be because pheromone-trapped beetles are not captured immediately after emergence, but rather after feeding on healthy pine trees, potentially allowing for nematode loss before collection. The density of \u003cem\u003eB. xylophilus\u003c/em\u003e in beetles peaks 2\u0026ndash;3 weeks post-emergence before declining (Enda, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e1972\u003c/span\u003e; Hosoda \u0026amp; Kobayashi, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e1978\u003c/span\u003e; Kim et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Mineo, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e1975\u003c/span\u003e). Considering this pattern, pheromone traps should be used primarily for monitoring rather than for direct PWD control.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003eComparison of temperature-dependent vector distribution across the survey sites\u003c/h2\u003e \u003cp\u003eConsidering that the daily average temperature varied among survey sites, a correlation analysis was performed to examine the relationship between temperature differences and the density of \u003cem\u003eM. alternatus\u003c/em\u003e, the primary vector of PWD, at different collection dates. In addition, we examined the relationship between vector density and annual variations.\u003c/p\u003e \u003cp\u003eA comparison of the average temperature and \u003cem\u003eM. alternatus\u003c/em\u003e density at each site showed a significant positive correlation at all locations: Site 1 (\u003cem\u003er\u0026thinsp;=\u003c/em\u003e\u0026thinsp;0.786, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01), Site 2 (\u003cem\u003er\u0026thinsp;=\u003c/em\u003e\u0026thinsp;0.744, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01), and Site 3 (\u003cem\u003er\u0026thinsp;=\u003c/em\u003e\u0026thinsp;0.755, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01) (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). Although correlation coefficients varied slightly among sites, all results indicated that \u003cem\u003eM. alternatus\u003c/em\u003e emergence timing was closely associated with daily average temperatures, with higher temperatures leading to increased beetle densities.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eA year-on-year comparison of \u003cem\u003eM. alternatus\u003c/em\u003e density and daily average temperature also revealed significant positive correlations for 2021 (\u003cem\u003er\u0026thinsp;=\u003c/em\u003e\u0026thinsp;0.717, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01), 2022 (\u003cem\u003er\u0026thinsp;=\u003c/em\u003e\u0026thinsp;0.751, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01), and 2023 (\u003cem\u003er\u0026thinsp;=\u003c/em\u003e\u0026thinsp;0.829, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01) (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e). Collectively, these findings suggest that the timing of emergence of \u003cem\u003eM. alternatus\u003c/em\u003e is affected by yearly temperature fluctuations and daily average temperatures, with warm temperatures associated with earlier and higher-density emergence than cold temperatures.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusions","content":"\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003eDistribution of B. xylophilus and its vectors\u003c/h2\u003e \u003cp\u003eIn this study, we investigated the distribution and density of PWN among dead pine trees (\u003cem\u003ePinus densiflora\u003c/em\u003e and \u003cem\u003ePinus thunbergii\u003c/em\u003e) across coastal and inland regions of South Korea, as well as the mortality rate of pine trees affected by PWD. In addition, the seasonal timing of \u003cem\u003eMonochamus alternatus\u003c/em\u003e attraction to aggregation pheromone traps was examined to clarify the emergence period of vector beetles in response to climate change.\u003c/p\u003e \u003cp\u003eA strong negative correlation was found between the densities of two nematode species in felled trees, \u003cem\u003eBursaphelenchus xylophilus\u003c/em\u003e and \u003cem\u003eB. mucronatus\u003c/em\u003e, suggesting a potential competitive interaction between them. Previous studies have shown that \u003cem\u003eB. mucronatus\u003c/em\u003e density is higher than \u003cem\u003eB. xylophilus\u003c/em\u003e in long-dead trees (Ha \u0026amp; Lee, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Park et al., \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). Considering the relationship between the highly pathogenic \u003cem\u003eB. xylophilus\u003c/em\u003e and the less pathogenic \u003cem\u003eB. mucronatus\u003c/em\u003e, targeting recently dead trees for PWD control may be more effective than removing long-dead trees.\u003c/p\u003e \u003cp\u003eDuring the three-year survey period (2021\u0026ndash;2023), an average of 30.1 \u003cem\u003eM. alternatus\u003c/em\u003e individuals were collected across all sites, among which 16.6 individuals (61.3%) were found to host \u003cem\u003eB. xylophilus\u003c/em\u003e. The higher proportion of infected beetles in areas with recurring PWD outbreaks suggests that \u003cem\u003eM. alternatus\u003c/em\u003e populations in these regions play a significant role in disease transmission. Considering that the average flight distance of \u003cem\u003eM. alternatus\u003c/em\u003e is 8.0 km (National Institute of Forest Science, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), preventive tree injections and chemical vector control measures should be prioritized within an 8 km radius of infected forest areas, particularly during the \u003cem\u003eM. alternatus\u003c/em\u003e emergence period.\u003c/p\u003e \u003cp\u003eA significant positive correlation was found between daily average temperature and \u003cem\u003eM. alternatus\u003c/em\u003e collection density across all survey sites. The first beetle collection occurred when the average temperature exceeded 20\u0026deg;C. In addition, the earlier the temperature increased in May, the earlier beetles were collected, suggesting that rising temperatures accelerate emergence. Considering the ongoing trend of rapid temperature increases due to climate anomalies in South Korea, continued monitoring of \u003cem\u003eM. alternatus\u003c/em\u003e emergence timing is crucial for determining the optimal timing of control measures.\u003c/p\u003e \u003c/div\u003e"},{"header":"Statements and Declarations","content":"\u003cp\u003e\u003cstrong\u003e\u003cem\u003eAcknowledgements\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e:\u0026nbsp;\u003c/strong\u003eNone.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eAuthor contributions\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eChong Kyu\u0026nbsp;Lee: Conceptualization,\u0026nbsp;Project administration,\u0026nbsp;Investigation,\u0026nbsp;Supervision,\u0026nbsp;Writing—review \u0026amp; editing, Resources, Methodology,\u0026nbsp;Formal analysis\u003c/p\u003e\n\u003cp\u003eHyun Kim: Conceptualization,\u0026nbsp;Methodology,\u0026nbsp;Formal analysis,\u0026nbsp;Writing—review \u0026amp; editing\u003c/p\u003e\n\u003cp\u003eMan-Leung Ha: Conceptualization, Investigation, Writing—original draft, Resources,\u0026nbsp;Software,\u0026nbsp;Data curation, Formal analysis, Validation, Visualization, Writing—original draft\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eFunding\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors did not receive support from any organization for the submitted work.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eData availability\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe data that support the findings of this study are available from the corresponding author, [M-L Ha], upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eConflict of interest\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that no known conflicts of interest exist.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eEthical Approval\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cbr\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eAbelleira, A., Picoaga, A., Mansilla, J. P., \u0026amp; Aguin, O. (2011). Detection of \u003cem\u003eBursaphelenchus xylophilus\u003c/em\u003e, causal agent of pine wilt disease on\u0026nbsp;\u003cem\u003ePinus pinaster\u003c/em\u003e in northwestern Spain.\u0026nbsp;\u003cem\u003ePlant Disease\u003c/em\u003e,\u0026nbsp;\u003cem\u003e95\u003c/em\u003e(6), 776. https://doi.org/10.1094/PDIS-12-10-0902\u003c/li\u003e\n \u003cli\u003eBaermann, G. 1917. Eine einfache methode zur auffindung von Ancylostomum (Nematoden) larven in erdproben. Geneeskd \u003cem\u003eTijdschr Ned Indie, 57\u003c/em\u003e, 131\u0026ndash;137.\u003c/li\u003e\n \u003cli\u003eCheng, H. R., Lin, M., Li, W., \u0026amp; Fang, Z. (1983). The occurrence of a pine wilting disease caused by a nematode found in Nanjing.\u0026nbsp;\u003cem\u003eForest Pest and Disease\u003c/em\u003e,\u0026nbsp;\u003cem\u003e4\u003c/em\u003e(1), 1\u0026ndash;5.\u003c/li\u003e\n \u003cli\u003eDwinell, L. D., \u0026amp; Nickle, W. R. (1989).\u0026nbsp;\u003cem\u003eAn overview of the pine wood nematode ban in North America\u003c/em\u003e. General Technical Report SE-55. USDA Forest Service.\u003c/li\u003e\n \u003cli\u003eEnda, N. (1972). Removing dauer larvae of\u0026nbsp;\u003cem\u003eBursaphelenchus lignicolus\u003c/em\u003e from the body of\u0026nbsp;\u003cem\u003eMonochamus alternatus\u003c/em\u003e.\u0026nbsp;\u003cem\u003eTransactions of the Annual Meeting of the Kanto Branch of the Japanese Forestry Society,\u003c/em\u003e \u003cem\u003e24\u003c/em\u003e, 32.\u003c/li\u003e\n \u003cli\u003eEnda, N. (1989). The status of pine wilt disease caused by\u0026nbsp;\u003cem\u003eBursaphelenchus xylophilus\u003c/em\u003e (Steiner et Buhrer) Nickle and its control in Korea. \u003cem\u003eJournal of Korean Society of Forest Science\u003c/em\u003e,\u0026nbsp;\u003cem\u003e78\u003c/em\u003e(2), 248\u0026ndash;253. (in Korean)\u003c/li\u003e\n \u003cli\u003eFutai, K. (2008). Pine wilt in Japan: From first incidence to the present. In B. G. Zhao, K. Futai, J. R. Sutherland, \u0026amp; Y. Takeuchi (Eds.).\u0026nbsp;\u003cem\u003ePine wilt disease\u003c/em\u003e, (pp. 5\u0026ndash;12). Tokyo, Japan: Springer.\u0026nbsp;https://doi.org/10.1007/978-4-431-75655-2_2.\u003c/li\u003e\n \u003cli\u003eHa, M. L., \u0026amp; Lee, C. K. (2017). Study on the damage by pine wood nematode in black pine trees. \u003cem\u003eJournal of Forest and Environmental Science\u003c/em\u003e,\u0026nbsp;\u003cem\u003e33\u003c/em\u003e, 105\u0026ndash;112.\u003c/li\u003e\n \u003cli\u003eHirata, A., Nakamura, K., Nakao, K., Kominami, Y., Tanaka, N., Ohashi, H., Takano, K. T., Takeuchi, W., \u0026amp; Matsui, T. (2017). Potential distribution of pine wilt disease under future climate change scenarios.\u0026nbsp;\u003cem\u003ePLOS One\u003c/em\u003e,\u0026nbsp;\u003cem\u003e12\u003c/em\u003e(8), e0182837. https://doi.org/10.1371/journal.pone.0182837\u003c/li\u003e\n \u003cli\u003eHosoda, R., \u0026amp; Kobayashi, K. (1978). Drop-off procedures of the pine wood nematode from the pine sawyer (II).\u0026nbsp;\u003cem\u003eTransactions of the Annual Meeting of the Kanto Branch of the Japanese Forestry Society\u003c/em\u003e\u003cem\u003e,\u003c/em\u003e \u003cem\u003e29\u003c/em\u003e, 131\u0026ndash;133.\u003c/li\u003e\n \u003cli\u003eJung, J. K., Hong, E. J., Kim, T. G., \u0026amp; Jeong, J. C. (2018). Ground beetle (Coleoptera: Carabidae) assemblage structure in Taeanhaean national park: A comparison between coastal dune and windbreak forest.\u0026nbsp;\u003cem\u003eKorean Journal of Environment and Ecology\u003c/em\u003e,\u0026nbsp;\u003cem\u003e32\u003c/em\u003e(2), 147\u0026ndash;153. https://doi.org/10.13047/KJEE.2018.32.2.147\u003c/li\u003e\n \u003cli\u003eJung, J. K., Kwon, H. J., Kim, H., Kim, J. H., Nam, Y. W., Kim, D. S., \u0026amp; Jung, C. S. (2020). Changes in catch rate of\u0026nbsp;\u003cem\u003eMonochamus saltuarius\u003c/em\u003e (Coleoptera: Cerambycidae) relation to sexual maturation.\u0026nbsp;\u003cem\u003eKorean Journal of Applied Entomology\u003c/em\u003e,\u0026nbsp;\u003cem\u003e59\u003c/em\u003e(4), 295\u0026ndash;301.\u003c/li\u003e\n \u003cli\u003eKim, D. S., Lee, S. M., Chung, Y. J., Choi, K. S., Moon, Y. S., \u0026amp; Park, C. G. (2003). Emergence ecology of Japanese pine sawyer, \u003cem\u003eMonochamus alternatus\u003c/em\u003e (Coleoptera: Cerambycidae), a vector of pinewood nematode, \u003cem\u003eBursaphelenchus xylophilus\u003c/em\u003e. \u003cem\u003eKorean\u003c/em\u003e \u003cem\u003eJournal\u003c/em\u003e.\u0026nbsp;\u003cem\u003eApplied\u003c/em\u003e.\u0026nbsp;\u003cem\u003eEntomology\u003c/em\u003e, \u003cem\u003e42\u003c/em\u003e, 307\u0026ndash;313.\u003c/li\u003e\n \u003cli\u003eKim, D. S., Lee, S. M., Huh, H. S., Park, N. C., \u0026amp; Park, C. G. (2009). Escape of pine wood nematode,\u0026nbsp;\u003cem\u003eBursaphelenchus xylophilus\u003c/em\u003e, through feeding and oviposition behavior of\u0026nbsp;\u003cem\u003eMonochamus alternatus\u003c/em\u003e and\u0026nbsp;\u003cem\u003eM. saltuarius\u003c/em\u003e (Coleoptera: Cerambycidae) adults.\u0026nbsp;\u003cem\u003eKorean Journal of Applied Entomology\u003c/em\u003e,\u0026nbsp;\u003cem\u003e48\u003c/em\u003e(4), 527\u0026ndash;533. https://doi.org/10.5656/KSAE.2009.48.4.527\u003c/li\u003e\n \u003cli\u003eKim, J., Lee, S. M., Jung, Y. H., Kwon, Y. D., Kim, D. S., Lee, D. W., \u0026amp; Park, C. G. (2016). Field evaluation on the synergistic attractiveness of 2-(1-undecyloxy)-1-ethanol and ipsenol to\u0026nbsp;\u003cem\u003eMonochamus saltuarius\u003c/em\u003e.\u0026nbsp;\u003cem\u003eEntomological Research\u003c/em\u003e,\u0026nbsp;\u003cem\u003e46\u003c/em\u003e(1), 31\u0026ndash;35. https://doi.org/10.1111/1748-5967.12145\u003c/li\u003e\n \u003cli\u003eKishi, Y. (1995). Pine wood nematode and the Japanese pine sawyer. Tokyo, Japan: Thomas Company Ltd\u003cem\u003e.\u003c/em\u003e,\u0026nbsp;p.\u0026nbsp;302.\u003c/li\u003e\n \u003cli\u003eKnowles, K., Beaubien, Y., Wingfield, M. J., \u0026amp; French, D. W. (1983). The pinewood nematode new in Canada.\u0026nbsp;\u003cem\u003eForestry Chronicle\u003c/em\u003e,\u0026nbsp;\u003cem\u003e59\u003c/em\u003e(1), 40.\u003c/li\u003e\n \u003cli\u003eKobayashi, F., Yamane, A., \u0026amp; Ikeda, T. (1984). The Japanese pine sawyer beetle as the vector of pine wilt disease.\u0026nbsp;\u003cem\u003eAnnual Review of Entomology\u003c/em\u003e,\u0026nbsp;\u003cem\u003e29\u003c/em\u003e(1), 115\u0026ndash;135. https://doi.org/10.1146/annurev.en.29.010184.000555\u003c/li\u003e\n \u003cli\u003eKorea Forest Service. (2023).\u0026nbsp;\u003cem\u003eStatistical yearbook of forestry No. 53\u003c/em\u003e. Seoul, Republic of Korea: Korea Forest Service, p. 36.\u003c/li\u003e\n \u003cli\u003eKorea Meteorological Administration. (2023).\u0026nbsp;\u003cem\u003eClimate statistics analysis\u003c/em\u003e\u003cem\u003e.\u003c/em\u003e Retrieved\u0026nbsp;March 26, 2024\u0026nbsp;from https://data.kma.go.kr/climate/RankState/selectRankStatisticsDivisionList.do?pgmNo=179\u003c/li\u003e\n \u003cli\u003eKwon, T. S., Lim, J. H., Sim, S. J., Kwon, Y. D., Son, S. K., Lee, K. Y., Kim, Y. T., Park, J. W., Shin, C. H., Ryu, S. B., \u0026amp; Lee, C. K. (2006). Distribution patterns of\u0026nbsp;\u003cem\u003eMonochamus alternatus\u003c/em\u003e and\u0026nbsp;\u003cem\u003eM. saltuarius\u003c/em\u003e (Coleoptera: Cerambycidae) in Korea.\u0026nbsp;\u003cem\u003eJournal of Korean Forestry Society\u003c/em\u003e,\u0026nbsp;\u003cem\u003e95\u003c/em\u003e(5), 543.\u003c/li\u003e\n \u003cli\u003eLee, H. R., Lee, S. C., Lee, D. H., Choi, W. S., Jung, C. S., Jeon, J. H., Kim, J. E., \u0026amp; Park, I. K. (2017). Identification of the aggregation-sex pheromone produced by male\u0026nbsp;\u003cem\u003eMonochamus saltuarius\u003c/em\u003e, a major insect vector of the pine wood nematode.\u0026nbsp;\u003cem\u003eJournal of Chemical Ecology\u003c/em\u003e,\u0026nbsp;\u003cem\u003e43\u003c/em\u003e(7), 670\u0026ndash;678. https://doi.org/10.1007/s10886-017-0864-6\u003c/li\u003e\n \u003cli\u003eLee, M. Y., Lee, C. H., Ha, M. L., \u0026amp; Kim, H. (2023). The dynamics of pine wilt nematode (\u003cem\u003eBursaphelenchus xylophilus\u003c/em\u003e) in pine wilt disease infected trees on Gyeongsangnam-do, Sachun-City. \u003cem\u003eThe Journal of Korean Island\u003c/em\u003e, \u003cem\u003e35\u003c/em\u003e(1), 213\u0026ndash;227. https://doi.org/10.26840/JKI.35.1.213\u003c/li\u003e\n \u003cli\u003eLee, S. M., Jung, Y. H., Seo, S. T., Kim, D. S., \u0026amp; Lee, D. W. (2021). Comparison of nematicidal effect and residual amount by injection time and number of holes using emamectin benzoate via tree injection against pine wood nematode,\u0026nbsp;\u003cem\u003eBursaphelenchus xylophilus\u003c/em\u003e. Korean.\u0026nbsp;\u003cem\u003eJournal of Pesticide Sciences\u003c/em\u003e,\u0026nbsp;\u003cem\u003e25\u003c/em\u003e(4), 371\u0026ndash;378. (in Korean)\u003c/li\u003e\n \u003cli\u003eLu, Q., Wang, W., Liang, J., Yan, D., Jia, X., \u0026amp; Zhang, X. (2005). Potential suitability assessment of\u0026nbsp;\u003cem\u003eBursaphelenchus xylophilus\u003c/em\u003e in China. Forest Research Chinese Academy of Forestry,\u0026nbsp;\u003cem\u003e18\u003c/em\u003e(4), 460\u0026ndash;464.\u003c/li\u003e\n \u003cli\u003eMamiya, Y. (1983). Pathology of the pine wilt disease caused by\u0026nbsp;\u003cem\u003eBursaphelenchus xylophilus\u003c/em\u003e.\u0026nbsp;\u003cem\u003eAnnual Review of Phytopathology\u003c/em\u003e,\u0026nbsp;\u003cem\u003e21\u003c/em\u003e(1), 201\u0026ndash;220. https://doi.org/10.1146/annurev.py.21.090183.001221\u003c/li\u003e\n \u003cli\u003eMamiya, Y. (1988). History of pine wilt disease in Japan.\u0026nbsp;\u003cem\u003eJournal of Nematology\u003c/em\u003e,\u0026nbsp;\u003cem\u003e20\u003c/em\u003e(2), 219\u0026ndash;226.\u003c/li\u003e\n \u003cli\u003eMamiya, Y., \u0026amp; Enda, N. (1972). Transmission of\u0026nbsp;\u003cem\u003eBursaphelenchus lignicolus\u003c/em\u003e (Nematoda: Aphelenchoididae) by\u0026nbsp;\u003cem\u003eMonochamus alternatus\u003c/em\u003e (Coleoptera: Cerrambycidae).\u0026nbsp;\u003cem\u003eNematologica\u003c/em\u003e,\u0026nbsp;\u003cem\u003e18\u003c/em\u003e, 159\u0026ndash;162.\u003c/li\u003e\n \u003cli\u003eMineo, K. (1975). Drop-off of pine wood nematodes from the pine sawyer and their invasion of pine trees.\u0026nbsp;\u003cem\u003eTransactions of the Annual Meeting of the Kanto Branch of the Japanese Forestry Society,\u003c/em\u003e \u003cem\u003e26\u003c/em\u003e, 275\u0026ndash;278.\u003c/li\u003e\n \u003cli\u003eMota, M. M., Braasch, H., Bravo, M. A., Penas, A. C., Burgermeister, W., Metge, K., \u0026amp; Sousa, E. (1999). First report of\u0026nbsp;\u003cem\u003eBursaphelenchus xylophilus\u003c/em\u003e in Portugal and in Europe.\u0026nbsp;\u003cem\u003eNematology\u003c/em\u003e,\u0026nbsp;\u003cem\u003e1\u003c/em\u003e(7), 727\u0026ndash;734. https://doi.org/10.1163/156854199508757\u003c/li\u003e\n \u003cli\u003eMyers, R. F. (1988). Pathogenesis in pine wilt caused by pinewood nematode,\u0026nbsp;\u003cem\u003eBursaphelenchus xylophilus\u003c/em\u003e.\u0026nbsp;\u003cem\u003eJournal of Nematology\u003c/em\u003e,\u0026nbsp;\u003cem\u003e20\u003c/em\u003e(2), 236\u0026ndash;244.\u003c/li\u003e\n \u003cli\u003eNational Institute of Forest Science. (2023). A study on the establishment of a comprehensive management system for prevention of the spread of pine nematode damage.\u0026nbsp;\u003cem\u003eNational Institute of Forest Science Research Report, 23\u003c/em\u003e(28), 14\u0026ndash;22.\u003c/li\u003e\n \u003cli\u003ePajares, J. A., Alvarez, G., Ibeas, F., Gallego, D., Hall, D. R., \u0026amp; Farman, D. I. (2010). Identification and field activity of a male-produced aggregation pheromone in the pine sawyer beetle,\u0026nbsp;\u003cem\u003eMonochamus galloprovincialis\u003c/em\u003e.\u0026nbsp;\u003cem\u003eJournal of Chemical Ecology\u003c/em\u003e,\u0026nbsp;\u003cem\u003e36\u003c/em\u003e(6), 570\u0026ndash;583. https://doi.org/10.1007/s10886-010-9791-5\u003c/li\u003e\n \u003cli\u003ePark, M. H. (2013). Diversity and distribution of beetles (\u003cem\u003eColeoptera Carabidae\u003c/em\u003e) in Jangsan (Mt), Busan. M.D. Thesis, Kyeongnam National Univ. of Sci. and Tech. Jinju, p. 43.\u003c/li\u003e\n \u003cli\u003ePark, S. C., Moon, Y. S., \u0026amp; Kim, D. S. (2014). Low-pathogenic pinewood nematode found in dead trees and resistance of pines induced by its pre-inoculation.\u0026nbsp;\u003cem\u003eKorean Journal of Applied Entomology\u003c/em\u003e,\u0026nbsp;\u003cem\u003e53\u003c/em\u003e(2), 141\u0026ndash;147. https://doi.org/10.5656/KSAE..2014.03.0.013\u003c/li\u003e\n \u003cli\u003eRutherford, T. A., \u0026amp; Webster, J. M. (1987). Distribution of pine wilt disease with respect to temperature in North America, Japan, and Europe.\u0026nbsp;\u003cem\u003eCanadian Journal of Forest Research\u003c/em\u003e,\u0026nbsp;\u003cem\u003e17\u003c/em\u003e(9), 1050\u0026ndash;1059. https://doi.org/10.1139/x87-161\u003c/li\u003e\n \u003cli\u003eSAS Institute Inc. (2003).\u0026nbsp;\u003cem\u003eSAS/STAT statistical software\u003c/em\u003e. (version 9.1). Cary, NC: SAS Publishing.\u003c/li\u003e\n \u003cli\u003eSutherland, J. R., Ring, F. M., \u0026amp; Seed, J. E. (1991). Canadian conifers as hosts of the pinewood nematode (\u003cem\u003eBursaphelenchus xylophilus\u003c/em\u003e): Results of seedling inoculations.\u0026nbsp;\u003cem\u003eScandinavian Journal of Forest Research\u003c/em\u003e,\u0026nbsp;\u003cem\u003e6\u003c/em\u003e(1\u0026ndash;4), 209\u0026ndash;216. https://doi.org/10.1080/02827589109382662\u003c/li\u003e\n \u003cli\u003eXu, Q., Zhang, X., Li, J., Ren, J., Ren, L., \u0026amp; Luo, Y. (2023). Pine wilt disease in Northeast and Northwest China: A comprehensive risk review. \u003cem\u003eForests\u003c/em\u003e, \u003cem\u003e14\u003c/em\u003e(2), 174. https://doi.org/10.3390/f14020174\u003c/li\u003e\n \u003cli\u003eYi, C. K., Byun, B. H., Park, J. D., Yang, S. I., \u0026amp; Chang, K. H. (1989). First finding of the pine wood nematode. \u003cem\u003eBursaphelenchus xylophilus\u003c/em\u003e (Sterner et Buhrer) Nickle and its insect vector in Korea. \u003cem\u003eResearch Reports of the Forestry Research Institute (Seoul)\u003c/em\u003e, \u003cem\u003e38\u003c/em\u003e, 141\u0026ndash;149. (in Korean)\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":false,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"european-journal-of-plant-pathology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ejpp","sideBox":"Learn more about [European Journal of Plant Pathology](http://link.springer.com/journal/10658)","snPcode":"10658","submissionUrl":"https://www.editorialmanager.com/ejpp/default2.aspx","title":"European Journal of Plant Pathology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Bursaphelenchus xylophilus, Monochamus alternatus, nematode, pine wood","lastPublishedDoi":"10.21203/rs.3.rs-6261204/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6261204/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn this study, we investigated the distribution and density of the pine wood nematode \u003cem\u003eBursaphelenchus xylophilus\u003c/em\u003ein recently dead pine trees in coastal and inland regions ofSouth Korea, as well as the mortality rate of pine trees affected by pine wilt disease (PWD). In addition, we examined the seasonal emergence patterns of the Japanese pine sawyer \u003cem\u003eMonochamus alternatus\u003c/em\u003e, the primary PWD vector, by monitoring its attraction to aggregation pheromone traps,to assess climate-driven variations in emergence timing. Surveys were conducted in May and June, from 2021 to 2023,across the three PWD-affected regions. In total, 35, 39, and 35 female \u003cem\u003eM. alternatus\u003c/em\u003eindividuals were collected in 2021, 2022, and 2023, respectively, and47, 55, and 50 males were collected, respectively. A density comparison between \u003cem\u003eB. xylophilus\u003c/em\u003e and the co-occurring low-pathogenic \u003cem\u003eB\u003c/em\u003e.\u003cem\u003e mucronatus \u003c/em\u003ein the felled trees revealed a strong negative correlation, suggesting a potential competitive interaction between the two nematode species. In addition, \u003cem\u003eM. alternatus\u003c/em\u003edensity was significantly positively correlated with thedaily average temperature (\u003cem\u003er =\u003c/em\u003e 0.786, 0.744, and 0.755 at Sites 1, 2, and 3, respectively), indicating that rising temperatures are associated with earlier vector emergence.\u003c/p\u003e","manuscriptTitle":"Distribution of pine wood nematodes and their vectors","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-04-25 15:24:33","doi":"10.21203/rs.3.rs-6261204/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2025-04-22T09:01:56+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-04-14T06:42:05+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"European Journal of Plant Pathology","date":"2025-03-24T05:54:20+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-03-24T04:44:20+00:00","index":"","fulltext":""},{"type":"submitted","content":"European Journal of Plant Pathology","date":"2025-03-19T07:42:15+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"european-journal-of-plant-pathology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ejpp","sideBox":"Learn more about [European Journal of Plant Pathology](http://link.springer.com/journal/10658)","snPcode":"10658","submissionUrl":"https://www.editorialmanager.com/ejpp/default2.aspx","title":"European Journal of Plant Pathology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"c8e2cdb8-fda7-4bf2-9c05-e05e471c3959","owner":[],"postedDate":"April 25th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-04-25T15:24:33+00:00","versionOfRecord":[],"versionCreatedAt":"2025-04-25 15:24:33","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6261204","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6261204","identity":"rs-6261204","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}