Impacts of the pest wood-boring beetle, Eupromus ruber, on Lauraceae species in temperate coastal forests

Impacts of the pest wood-boring beetle, Eupromus ruber, on Lauraceae species in temperate coastal forests | 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 Case Report Impacts of the pest wood-boring beetle, Eupromus ruber, on Lauraceae species in temperate coastal forests Ryota Asano, Makoto Nakata, Akihiro Nakamura, Tomohiro Yoshida This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8025870/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Context : Lauraceae species have become key components of temperate coastal forests, particularly following the decline of pine trees. The wood-boring beetle Eupromus ruber , known to infest Lauraceae, is expanding its distribution in these forests, potentially impacting tree health and forest ecosystems. Aims : This study aims to investigate the invasion of E. ruber , identify preferred Lauraceae host trees, and evaluate whether oviposition and larval boring increase the risk of stem breakage in temperate coastal forests. Methods: Field surveys were conducted in coastal forests to assess the extent of damage caused by E. ruber on its host tree, Machilus thunbergii . The number of oviposition scars and stem breakage were recorded for individual trees. Generalized linear models (GLMs) were used to evaluate environmental factors affecting E. ruber activity and the association of E. ruber with stem breakage in its host. Results : GLM analysis revealed a positive correlation between the number of oviposition scars and both tree height and relative photosynthetic photon flux density (rPPFD), indicating that E. ruber preferentially oviposits on taller, sun-exposed M. thunbergii trees. Stem breakage was associated with the presence of oviposition and larval boring, suggesting that E. ruber activity increases the risk of stem failure in its host. Conclusion E. ruber infestation weakens M. thunbergii stems, increasing breakage risk in snowy coastal forests. Monitoring and integrated management are crucial for maintaining forest stability. Cerambycidae Forest damage prevention Forest management Invasion biology Tree breakage Wood-boring pests Figures Figure 1 Figure 2 Key Messages The wood-boring beetle Eupromus ruber is expanding its distribution in temperate coastal forests along the Sea of Japan, affecting Lauraceae species. Field surveys show that taller, sun-exposed trees are preferentially oviposited, and beetle activity contributes to stem breakage and fungal invasion. Monitoring and integrated pest management are essential for forest conservation. 1. Introduction Coastal forests serve as a protective buffer, safeguarding communities from wind-blown sand, strong winds, erosion, and tsunamis, thereby enhancing local resilience (Shepard et al. 2011 ; Chang and Mori 2021 ; Zhu et al. 2024 ). In response to their ecological importance, global conservation and afforestation efforts have been initiated to preserve these ecosystems (Wu et al. 2021 ; Xie et al. 2021 ; Song et al. 2023 ). However, coastal forests are increasingly threatened by various stressors and disturbances, particularly invasive pests (Trumbore et al. 2015 ). The introduction of such species has been associated with severe declines in tree health across many coastal regions (Koch and Smith 2008 ; Firmino et al. 2017 ; Cobb et al. 2020 ). As biological invasions continue (Ramsfield et al. 2016 ; Green et al. 2023 ), monitoring trends in invasive pest populations is necessary to protect the ecosystem services provided by coastal forests. Coastal pine forests are widely distributed across East Asia (Han et al. 2009 ; Bitog et al. 2011 ), and provide essential ecosystem services to coastal communities (Kusumoto et al. 2020 ; Torita et al. 2021 ; Omori et al. 2024 ). In Japan, however, these forests have been severely affected by pine wilt disease, caused by the pine wood nematode Bursaphelenchus xylophilus , which is thought to have been introduced from North America in the early 1900s (Mamiya 1988 ). The disease has contributed to the decline of coastal forests in Japan (Mamiya 1988 ; Teramoto and Shimokawa 2011 ). Once established, the nematode spreads rapidly through vector insects and human activity (Vicente et al. 2012 ), making its management costly and challenging (Back et al. 2024 ). Historically, pine needle gathering was routinely practiced as a fuel resource in Pinus thunbergii coastal forests between the 1950s and 1960s, where it served as a household fuel resource (Konta 2001 ). The decline of this practice following the transition to alternative fuels resulted in the accumulation of organic matter on the forest floor, which facilitated the invasion of broadleaf species (Konta 2001 ). Reduced removal of fallen leaves and branches, coupled with broadleaf encroachment, further promoted nutrient accumulation in the soil (Fujita and Nakata 2001 ). This nutrient enrichment has driven a gradual shift toward plantations dominated by native Lauraceae species, such as Machilus thunbergii and Neolitsea sericea , in place of pines that are better adapted to nutrient-poor soils (Fujita and Nakata 2001 ; Yoneyama and Kamitani 2018 ). However, monoculture plantations remain vulnerable to pest and disease outbreaks compared with mixed-species forests (Jactel and Brockerhoff 2007 ; Jactel et al. 2017 ; Stemmelen et al. 2023 ). Supporting this, European studies have shown that tree species richness at the plot or stand scale is negatively correlated with the abundance of invasive forest pests (Jactel et al. 2006 ; Guyot et al. 2015 ). In recent years, cases of invasive wood-boring beetles overcoming biogeographical barriers and successfully establishing their populations have been reported worldwide (Garonna et al. 2013 ; Horrocks et al. 2024 ). The wood-boring beetle Eupromus ruber is widely distributed in East Asia (Lim et al. 2013 ) and infests Lauraceae trees. Adult beetles feed on the branches and leaves of these trees (Kojima and Hayashi 1969 ; Hayashi et al. 1984 ). In the warm-temperate zones of Japan, E. ruber has been reported to infest Lauraceae trees (Kojima and Hayashi 1969 ). The larvae of this species bore into the cambial layer of young trunks and branches of host trees and damage the cambium (Kojima 1931 ; Banno and Yamagami 1989 ). Although E. ruber infestation typically does not result in the death of Lauraceae species (Banno and Yamagami 1989 ), severe damage has been observed in Lauraceae trees planted as street trees (Ohga et al. 1995 ). These infestations, which affect healthy parts of the tree, can facilitate fungal invasions (Ohga et al. 1995 ). Furthermore, Lauraceae species planted in coastal forests have shown signs of branch and trunk breakage due to E. ruber infestation (Sugimoto and Yamada 2007 ). In coastal areas with heavy winter snowfall, there is concern that Lauraceae species infested by E. ruber may experience additional physical damage from the weight of accumulated snow. This study investigated pest damage critical for the maintenance and management of coastal forests dominated by evergreen broadleaf trees of Lauraceae, with the goal of developing effective pest management strategies. Specifically, we: 1) identified the damage caused by the pest species E. ruber to Lauraceae trees in coastal forests and examined the pest’s oviposition site preferences, and 2) provided recommendations for pest control measures to mitigate damage in these coastal forests. The introduction should open to a few explicit working hypotheses or at least a few explicit research questions; if none is available, the manuscript may be directly returned to the authors. 2. Material and methods Choose your number of sections as appropriate. 2.1 Study area The study was conducted in 2011 and 2012 in the coastal forests of Niigata City, located in central Japan. The mean annual temperature and precipitation recorded between 1980 and 2020 in the study area were 13.9 °C and 1825.9 mm, respectively (Japan Meteorological Agency 2024). The region experiences heavy snowfall, with a mean annual maximum recorded snow depth of 35.8 cm during the same period (Japan Meteorological Agency, 2024). The distribution of E. ruber is limited to areas west of Tokyo on the Pacific side and west of Ishikawa Prefecture along the Sea of Japan coast in Japan, and it was not recorded in Niigata City until the early 2000s (Ministry of Agriculture, Forestry and Fisheries 1998; Ohbayashi and Niisato 2007). However, Lauraceae trees, including M. thunbergii and N. sericea, have been repeatedly planted in the coastal forests of Niigata City (Koda 2004; Takeda and Kaneko 2007). It is highly probable that E. ruber invaded the area through this process as an alien species. 2.2 Distribution of tree damage caused by E. ruber We first conducted a survey from May to October 2011 to determine the distribution of E. ruber by examining its host tree, M. thunbergii , for signs of damage. The primary aim was to determine the extent of the beetle’s range expansion from the coastal forests at the foothills of Mt. Kakuda, where it had first been confirmed. The survey area stretched along a coastal forest zone from Mt. Kakuda (37.7976°N, 138.8263°E) to Sekiya (37.9214°N, 139.0279°E) (Fig. 1), and was divided into four sites, labeled Site A to Site D, to allow for a systematic assessment of the beetle’s range expansion along the coastline. In addition, we investigated E. ruber occurrence in Sakata Park (37.8189°N, 138.8799°E) and Uwasekigata Park (37.7908°N, 138.8664°E), where M. thunbergii trees have been planted in urban parks adjacent to the coastal forest. These parks were selected simply to document the distribution of E. ruber within the city area. Machilus thunbergii grows vigorously in relatively open areas, primarily regenerating in gaps and along forest edges (Yamamoto, 1992; Takyu & Ohsawa, 1997; Takyu, 1998; Yamagawa et al., 2007). We surveyed M. thunbergii trees located along forest edges by cycling along the road that runs through Sites A to D. In addition, in parks within Sites C and D, as well as in Sakata Park and Uwasekigata Park, where walking trails were available, we walked along the trails to search for M. thunbergii trees along the forest edges. E. ruber produces distinctive elliptical oviposition scars by peeling the bark (Appendix Fig. 1A). Its larvae expel frass through fecal discharge holes, and newly emerged adults exit the tree through 7–8 mm diameter exit holes (Appendix Fig. 1B, C) (Kojima & Hayashi, 1969). In Japan, E. ruber is the only insect known to leave such distinctive signs on living Lauraceae trees (Kojima & Hayashi, 1969; Ministry of Agriculture, Forestry and Fisheries, 1998; Ohbayashi & Niisato, 2007). Upon visually identifying M. thunbergii trees, we approached them to closely inspect for these signs of damage. Trees showing such signs were recorded as part of the beetle’s distribution. For tall M. thunbergii trees, we climbed the trees directly to check for damage. 2.3 Damage Assessment of Lauraceae Species by E. ruber From August to October 2012, we surveyed the damage and oviposition patterns of E. ruber in the coastal forests at the foothills of Mt. Kakuda. This forest stand was selected because E. ruber invasion had been confirmed in the area, and vegetation succession appeared to be progressing following pine wilt disease, with species of the family Lauraceae particularly M. thunbergii and N. sericea regenerating and becoming increasingly dominant. The forest stand is divided by a road into a seaward stand (Plot 1) and an inland stand (Plot 2) (Fig. 1). Plot 1, with a maximum forest belt width of about 270 m and a total area of approximately 11.8 ha, underwent thinning around two years ago. The stand is primarily composed of Pinus thunbergia (Pinaceae), with few other tree species. Deciduous broadleaf species such as Cerasus spp. (Rosaceae) and Zelkova serrata (Ulmaceae) are rare. Most of the M. thunbergii and N. sericea (both Lauraceae) trees are coppice regeneration shoots following thinning, with tree heights mostly under 3 m. Plot 2 has a maximum forest belt width of about 130 m and a total area of around 4.9 ha. This stand is a mixed multilayer forest, with a canopy dominated by P. thunbergii , a subcanopy layer comprising Acer pictum (Sapindaceae), Quercus serrata (Fagaceae), Lauraceae species M. thunbergii , and N. sericea , and an understory dominated by Viburnum dilatatum (Viburnaceae) and Morus australis (Moraceae). In these plots, we surveyed all Lauraceae species, including M. thunbergii , that were at least 1.3 m tall to assess damage caused by E. ruber . For all surveyed Lauraceae species, we measured the diameter at breast height (DBH) and climbed taller trees to inspect higher sections directly. Additionally, for M. thunbergii , we recorded tree height, tree position, the number of oviposition scars, and the height and diameter of these scars. The study area consisted of two plots differing in management status: Plot 1 (thinned area) and Plot 2 (unthinned area). Each plot contained forest edges (trees within five meters of the forest boundary or road) and forest interiors (trees farther inside the forest). Tree positions were classified based on their location as either forest edge or forest interior. Oviposition scars were counted, with a focus on newer scars likely made in the current year. These newer scars were identified by the absence of discoloration on the scraped area and the lack of bark regeneration or swelling around the scar. To measure oviposition height, one researcher held a measuring pole from the ground while another climbed the tree to confirm its position. The diameter of the tree at the oviposition site was measured with calipers within the accessible range. Additional data on solar radiation and crown base height were recorded for M. thunbergii trees taller than 3 m. In September 2012, we measured solar radiation using a photon meter (Digital Ohm Co. Ltd: HD230.2) to assess the photosynthetic photon flux density (PPFD). To calculate the relative photosynthetic photon flux density (rPPFD), measurements were taken three times each at a standardized height of 1.8 m at four evenly spaced points around each tree, with simultaneous measurements on bare ground. The relative photosynthetic photon flux density for each point was calculated and averaged. The crown length was determined by subtracting the crown base height from the total tree height, and the crown ratio (%) was calculated as the crown length divided by the total tree height. 2.4 Host tree damage During the surveys in Plot 1 and Plot 2, we assessed M. thunbergii trees over 3 m in height for bole breakage, dieback, and the presence of fungal fruiting bodies. To examine the effects of E. ruber on bole breakage and dieback, we recorded the extent of damage at break points caused by E. ruber and assessed trunk damage due to its infestation. For M. thunbergii trees with confirmed bole breakage, we measured the length of the broken bole from the base to the break point and from the break point to the broken tip to estimate the tree’s original height before breakage. The extent of E. ruber -related damage at break points was determined by checking for oviposition scars and boring marks. To assess fungal invasion associated with E. ruber infestation, we recorded the presence of fungal fruiting bodies, oviposition scars, and boring marks in areas where fungi were found. For trees showing dieback, we also recorded cracks, pressure marks, and any signs of E. ruber damage. The level of E. ruber -induced damage was assessed on the trunk below the crown base. The damage extent was evaluated based on the continuous oviposition scars, fecal discharge holes, and adult emergence holes of E. ruber along the trunk in relation to unaffected areas. Eupromus ruber larvae hatch from oviposition scars and create fecal discharge holes at various points along the tunnel when boring into the tree. These fecal discharge holes, along with adult emergence holes, contribute to continuous damage. Damage levels were classified into five categories based on the percentage of affected trunk area: Level 1 (0%), Level 2 (less than 5%), Level 3 (5–15%), Level 4 (15–30%), and Level 5 (more than 30%). 2.5 Statistical analysis We used a generalized linear model (GLM) with a Poisson error distribution to examine the factors influencing the number of E. ruber oviposition scars. The analysis focused on M. thunbergii trees taller than 3 m, with the number of oviposition scars as the response variable. Explanatory variables included tree height, crown ratio (%), relative photosynthetic photon flux density (rPPFD, %), tree location (edge vs. interior forest), and management status (thinned vs. unthinned plots). Additionally, we applied logistic regression to explore the factors influencing bole breakage in M. thunbergii trees. This analysis also focused on trees taller than 3 m, using the presence or absence of bole breakage (1 = breakage, 0 = no breakage) as the response variable. Explanatory variables included E. ruber -induced damage level, tree height, rPPFD, tree location, and management status. To address potential multicollinearity among explanatory variables, we calculated the Variance Inflation Factor (VIF) and excluded variables with VIF ≥ 5 to ensure all retained variables remained below this threshold (Akinwande 2015). We then constructed multiple GLMs and logistic regression models, testing all possible combinations of explanatory variables. The optimal model was selected using a stepwise method based on the Akaike Information Criterion (AIC) (Lander 2013). Our analyses included only main effects, without interaction terms. All statistical analyses were conducted using R 2.14.0 (R Core Team 2012). 3. Results 3.1 Distribution of E. ruber at the Study Sites The survey identified signs of E. ruber activity (e.g., oviposition scars and larval boring) in Site A, Sakata Park, and Uwasekigata Park. However, no signs of the beetle were found in Site B, where only small M. thunbergii saplings were observed. Although M. thunbergii trees were found in Sites C and D, no evidence of E. ruber -induced damage was recorded. 3.2 Damage by E. ruber in Lauraceae Species Across Plot 1 and Plot 2, a total of 401 Lauraceae trees were surveyed, comprising M. thunbergii (253 trees), Neolitsea sericea (146 trees), Cinnamomum japonicum (1 tree), and Laurus nobilis (1 tree). Damage caused by E. ruber , including oviposition scars, frass discharge holes, and expelled frass, was observed on 128 out of 253 M. thunbergii trees and on the single C. japonicum tree. No signs of damage were detected on N. sericea or L. nobilis (Appendix Fig. 2A, B). Among M. thunbergii , the damage was observed even in trees with a DBH of less than 5 cm, and all M. thunbergii and C. japonicum trees with a DBH of 5 cm or more were affected by E. ruber (Appendix Fig. 2C, D). In contrast, N. sericea trees, ranging from less than 5 cm to nearly 35 cm DBH, showed no signs of infestation. Similarly, the single L. nobilis tree, with a DBH under 5 cm, remained undamaged. 3.3 Oviposition by E. ruber and Environmental Factors in Plots 1 and 2 GLM analysis (Table 1) revealed that the number of E. ruber oviposition scars was significantly influenced by tree height (Coefficient = 0.36, p < 0.001), crown ratio (Coefficient = 0.02, p < 0.01), and rPPFD (Coefficient = 0.03, p < 0.001). Additionally, trees located at forest edges exhibited significantly higher oviposition scars (E = 0.52, p < 0.01). The height of oviposition points was strongly positively correlated with tree DBH (Spearman’s r = 0.796, p < 0.001), indicating a shift in oviposition preference from trunks to branches as trees grow larger (Fig. 2). Oviposition activity was most frequently observed on surfaces with a diameter of 2–4 cm, including both branches and trunks, with no activity observed on surfaces larger than 8 cm in diameter (Appendix Fig. 3). Table 1 A generalized linear model with the number of oviposition scars as the dependent variable (response variable) in the final model. Variables Estimate Std. Error t value p value Intercept -2.48 0.39 0.00 *** Tree height 0.36 0.05 0.18 *** Crown ratio 0.02 0.01 0.08 ** rPPFD (%) 0.03 0.01 0.11 *** Forest edge 0.52 0.18 0.08 ** ***: p<0.001, **: p<0.01, *: p<0.05 Among 138 M. thunbergii trees taller than 3 m, 110 (79.7%) were healthy, 27 (19.6%) exhibited bole breakage, and one (0.7%) was dead. Fruiting bodies of Pleurotaceae fungi were found on five non-broken trees, emerging from oviposition scars or exit holes created by E. ruber (Appendix Fig. 4A, B). All trees with bole breakage showed evidence of E. ruber damage, with both oviposition scars and boring marks present on 92.6% of damaged areas, while 7.4% had only boring marks (Appendix Fig. 4C, D, Appendix Fig. 5). Logistic regression analysis (Table 2) revealed that bole breakage was significantly positively associated with the extent of E. ruber damage (Coefficient = 0.78, p < 0.01) and rPPFD (Coefficient = 0.05, p < 0.01), while tree height had a significantly negative association (Coefficient = −0.6, p < 0.01). Although not statistically significant, trees located at forest edges tended to have higher rates of bole breakage compared to those located in the interior of the forest. The single dead tree observed in this study showed no signs of suppression damage or injury other than perforations caused by E. ruber larvae. Table 2 The final model of logistic regression analysis with the presence or absence of broken trunk in Machilus thunbergii as the dependent variable. Variables Estimate Standard Error t value p value Intercept -2.92 1.34 0.00 *** Damage level of Eupromus ruber 0.78 0.26 2.07 ** Tree height -0.6 0.23 -2.2 ** rPPFD (%) 0.05 0.02 1.69 ** Forest edge 0.81 0.57 0.92 n.s. ***: p<0.001, **: p<0.01, *: p 0.05 4. Discussion 4.1 Factors affecting bole damage by E. ruber This study confirmed E. ruber occurrence in Site A, Sakata Park, and Uwasekigata Park within Niigata City. However, it was not found in Site B, C, or D, indicating that at the time of the survey (2011 and 2012), its distribution remained localized and had not yet spread throughout the coastal forests of Niigata City. This suggests that the invasion of E. ruber is still in its early stages. The larvae of E. ruber primarily infest M. thunbergii , although they may occasionally bore into living Cinnamomum japonicum and Machilus japonica under rare conditions in Japan’s warm-temperate zones (Kojima and Hayashi 1969). In this study, signs of E. ruber oviposition and boring were observed in M. thunbergii (128 of 253 trees) and C. japonicum (1 of 1 tree), confirming that M. thunbergii is the primary host at the study site. In contrast, despite the broad size range of Neolitsea sericea trees surveyed, no signs of infestation were detected, suggesting that N. sericea is not a preferred host for oviposition. All M. thunbergii trees with a DBH greater than 5 cm exhibited signs of E. ruber damage, including oviposition scars and larval boring, consistent with observations from other warm-temperate habitats, where few trees show no signs of damage (Kojima and Hayashi 1969). Additionally, some M. thunbergii trees with a DBH smaller than 5 cm also showed signs of infestation, suggesting that eggs or larvae may already be present in relatively small trees. 4.2 Substrate Diameter and Oviposition Preferences Many species within the Cerambycidae family exhibit oviposition preferences based on substrate diameter (e.g. Morewood et al. 2003a; Lee and Lee, 2020; Turgeon et al. 2024). Similarly, E. ruber is thought to select oviposition sites based on branch diameter (Kojima and Hayashi 1969; Sugimoto and Yamada 2007). In this study, oviposition scars were found on both branches and boles, with oviposition points shifting from boles to branches as trees grew taller. Despite this shift, the substrate diameter at oviposition points remained concentrated between 2 and 4 cm, suggesting that diameter is a more critical factor than wood type or substrate height. This preference likely reflects a trade-off between the difficulty of penetrating bark and the availability of resources for larval development. Bark serves as a protective barrier for plant boles and branches (Ferrenberg and Mitton 2014; Rosell et al. 2016), and thicker bark—more common in larger-diameter substrates—poses higher energy costs for oviposition and may increase predation risk (Edwards and Linit, 1991; Rosell et al. 2016). Conversely, thinner branches, while easier to penetrate, offer fewer resources for larvae, potentially increasing mortality due to competition (Coulson 1979; Rice 1989; Hanks et al. 1991). Since E. ruber lays only 5–10 eggs per oviposition point (Kojima and Hayashi, 1969), selecting substrates of optimal diameter is essential for minimizing larval competition and improving survival rates. The observed resource preference may also be influenced by the scarcity of suitable oviposition sites resulting from the rapid growth of the E. ruber population. Invasive species often experience population surges in non-native ranges due to the absence of natural enemies and high host susceptibility (Wolfe et al. 2002; Brockerhoff and Liebhold 2017). The presence of numerous old oviposition scars in the study area suggests a rapid population increase, with branches and boles of suitable diameters already heavily utilized. Similar to other wood-boring beetles, such as Monochamus alternatus and M. scutellatus , which avoid previously used substrates to reduce intraspecific competition (Anbutsu and Togashi 1996, 2002; Peddle et al. 2002), E. ruber may have shifted to thinner, unused branches to mitigate competition in this study area. 4.3 Other Environmental Factors Affecting Oviposition Preferences E. ruber exhibited a preference for oviposition on M. thunbergii trees with greater height, higher crown ratios, higher rPPFD values, and those located at forest edges. Taller trees with higher crown ratios provide more branches of suitable diameter, increasing the availability of oviposition sites and potentially enhancing offspring survival by offering better protection from parasites, desiccation, and extreme weather conditions (Paulino-Neto et al. 2005). The preference for trees with higher rPPFD values may be explained by E. ruber ’s positive phototaxis. Similar patterns have been observed in other wood-boring insects, which frequently oviposit on trees in well-lit environments (Cárdenas and Gallardo 2013; Kautz et al. 2013; Kašák and Foit 2018). Additionally, M. thunbergii thrives in such conditions, regenerating primarily in forest gaps (Yamamoto 1992; Takyu and Ohsawa 1997; Takyu 1998; Yamagawa et al. 2007). Another wood-boring species, Anoplophora glabripennis , has been shown to utilize visual cues, particularly when adult beetles search for host plants from a distance (Lyu et al. 2023). Similarly, E. ruber may rely on visual cues to locate host trees in brighter environments, where reduced tree density enhances visibility. Furthermore, higher wood temperatures in sunlit areas may accelerate larval development, as reported in other wood-boring beetles (Graham 1925; Savely 1939). These factors collectively suggest that E. ruber selects trees in brighter environments or at forest edges to optimize offspring fitness. 4.4 Boles Damage and Associated Risks Infestation by wood-boring insects like E. ruber often leads to structural damage, including decay fungi invasion, branch drop, bole breakage, and, in severe cases, tree mortality (Sharifi et al. 1970; Nowak et al. 2001; Negussie et al. 2018; Monteys et al. 2021). In this study, 19.6% of surveyed M. thunbergii trees taller than 3 m exhibited bole breakage, and all cases were associated with E. ruber damage, as evidenced by oviposition scars or boring marks at the break points. Logistic regression analysis confirmed a positive relationship between the extent of E. ruber damage and the likelihood of bole breakage. Before reaching maturity, E. ruber larvae consume between 7 and 17 g of dry wood mass or between 12 and 33 cm³ in volume (Banno & Yamagami 1989). Their boring activity weakens the structural integrity of trees by forming cavities, an effect exacerbated by larval aggregation around oviposition sites (Sugimoto and Yamada 2007). Additionally, wood-boring beetle damage promotes the invasion of decay fungi (Ohga et al. 1995; Panzavolta et al. 2018; Linnakoski and Forbes 2019), which can lead to bole and root rot, thereby increasing the risk of tree collapse (Ding et al. 2020). In this study, Pleurotaceae fungi were frequently observed at E. ruber oviposition scars (Appendix Fig. 4B), highlighting the beetle’s role in facilitating fungal colonization and subsequent bole decay. The observed bole breakage rate (19.6%) was substantially higher than the 2.7% reported in other coastal forests affected by E. ruber (Sugimoto and Yamada 2007). This discrepancy may be attributed to the greater snowfall intensity at the study site, where the average maximum snow depth (35.8 cm, 1980–2020) was nearly eight times higher than that recorded in Sugimoto and Yamada’s study (4.3 cm, 1980–2020) (Japan Meteorological Agency, 2024). Evergreen broadleaf trees, such as M. thunbergii , retain their foliage in winter, making them more susceptible to snow accumulation and stem breakage (Givnish 2002; Chen and Sun 2010). The study area recorded a maximum snow depth of 81 cm in 2010 (Japan Meteorological Agency 2024), suggesting that trees weakened by E. ruber infestation may have sustained further damage due to heavy snow loads, resulting in increased bole breakage that year. 4.5 Tree Mortality Caused by E. ruber Infestation Previous studies suggest that M. thunbergii generally does not die solely from E. ruber damage (Banno and Yamagami 1989). In this study, only one dead M. thunbergii tree was observed, indicating that mortality due to E. ruber infestation alone is unlikely. However, for smaller-diameter trees, mortality may result from cumulative weakening caused by boring, bole breakage, or other forms of structural damage (Sugimoto and Yamada 2007). In certain longhorn beetles, such as Anoplophora glabripennis and Aromia bungii , larval boring into the cambium or wood can directly lead to tree death (Morewood et al. 2003b; Urano et al. 2022). 4.6 Pest Management in Coastal Forests This study demonstrated that E. ruber infestation in coastal forests leads to bole breakage in M. thunbergii , with damage exacerbated in regions with heavy snowfall. M. thunbergii has been planted in coastal forests even beyond the natural range of E. ruber (Nobori et al. 2004; Nitta and Kaneko, 2023), raising concerns that these cultivated trees may facilitate the beetle’s range expansion. To mitigate this risk, precautions should be taken to prevent the anthropogenic introduction of E. ruber into new areas. The study also revealed that E. ruber larvae can penetrate the interior of relatively small M. thunbergii trees with a DBH of less than 5 cm. Oviposition scars were observed on branches as thin as 2 cm in diameter (Kojima and Hayashi 1969). Therefore, thorough inspections for oviposition scars are essential when introducing M. thunbergii and C. japonicum to coastal forests. In contrast, N. sericea showed no signs of damage from E. ruber in the study area. Additionally, tall evergreen species, such as Ilex integra and Ternstroemia gymnanthera , which are expected to contribute to the diversity of coastal forests (Yamaguchi and Nakata 2008), may play a role in reducing pest impacts. Forests with higher tree species diversity are generally less susceptible to pest and disease outbreaks (Jactel and Brockerhoff 2007; Stemmelen et al. 2023; Field et al. 2025). Thus, promoting species diversity and selecting species adapted to local environments, rather than relying on monocultures, can help mitigate the risks posed by pests like E. ruber . The severity of pest damage varies according to species-specific traits and microclimatic conditions, highlighting the importance of understanding these factors to improve pest control efficiency (Naves et al. 2006; Mazaheri et al. 2011; Kautz et al. 2013; Jonsson et al. 2015; Mariño et al. 2016). In coastal forests already invaded by E. ruber , control efforts should focus on host trees, particularly M. thunbergii and C. japonicum . This study revealed that E. ruber prefers oviposition sites on M. thunbergii located in bright areas or at forest edges. Therefore, control measures should prioritize these areas, as well as isolated trees and those in canopy gaps caused by pine wilt disease. Physical control methods, such as wrapping tree trunks with netting, can prevent wood-boring beetles like E. ruber from boring and laying eggs (Kain et al. 2010; Ranger et al. 2019; Yamamoto et al. 2024). Covering trunks with plastic or burlap is particularly effective for young M. thunbergii trees, preventing boles and branches from breaking caused by oviposition. Early application and removal of branches with oviposition scars are recommended to eliminate eggs and larvae. This study also found that oviposition was concentrated on trees with a high crown ratio. Increasing tree density in coastal forests to promote early dieback of lower branches or conducting selective pruning may reduce oviposition damage. However, these practices could increase the height-to-diameter ratio of trees, making them more vulnerable to wind and snow damage. Therefore, pest management strategies should strike a balance between the risks of E. ruber infestation and the structural stability of trees, and regular monitoring is essential to adapt management practices accordingly. 5. Conclusion This study revealed that E. ruber infestation causes significant bole damage in M. thunbergii within coastal forests, particularly in regions with heavy snowfall, where weakened stems are more prone to breakage. Since M. thunbergii has been widely planted beyond the beetle’s natural range, careful management is required to prevent further spread. Regular inspections for oviposition scars, especially on thin branches, and early removal of infested parts are crucial to limit damage. Increasing tree species diversity, adjusting stand density, and prioritizing monitoring in bright or edge environments where E. ruber is most active can reduce infestation risks. Integrated pest management strategies balancing pest control and forest stability are essential for the long-term conservation and restoration of coastal forests. Declarations Author Contribution Conceptualization: RA, MN; Methodology: RA, MN; Formal analysis and investigation: RA; Writing – original draft preparation: RA; Writing – review and editing: MN, AN, TY; Funding acquisition: MN; Resources: MN; Supervision: MN, TY.The authors read and approved the final manuscript. Acknowledgement We would like to express our gratitude to Dr. Shota Deguchi and Mr. Daisuke Ataka for their collaboration in this study. References Akinwande MO, Dikko HG, Samson A (2015) Variance inflation factor: As a condition for the inclusion of suppressor variable (s) in regression analysis. Open Journal of Statistics 5: 754–767. https://doi.org/10.4236/ojs.2015.57075 Anbutsu H, Togashi K (1996) Deterred oviposition of Monochamus alternatus (Coleoptera: Cerambycidae) on Pinus densiflora bolts from oviposition scars containing eggs or larvae. 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University","correspondingAuthor":false,"prefix":"","firstName":"Makoto","middleName":"","lastName":"Nakata","suffix":""},{"id":546470421,"identity":"65dc7782-2a2f-4abd-95c9-5aca023894d2","order_by":2,"name":"Akihiro Nakamura","email":"","orcid":"","institution":"Chinese Academy of Sciences","correspondingAuthor":false,"prefix":"","firstName":"Akihiro","middleName":"","lastName":"Nakamura","suffix":""},{"id":546470422,"identity":"575795f9-eef5-476a-9bfc-cbb6e9c8e54b","order_by":3,"name":"Tomohiro Yoshida","email":"","orcid":"","institution":"Tokyo University of Agriculture and Technology","correspondingAuthor":false,"prefix":"","firstName":"Tomohiro","middleName":"","lastName":"Yoshida","suffix":""}],"badges":[],"createdAt":"2025-11-04 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06:47:46","extension":"html","order_by":25,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":215337,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8025870/v1/eeaca5882f777e4e9514b3a0.html"},{"id":96592823,"identity":"3260d289-c218-413c-b12c-af472d3e74d1","added_by":"auto","created_at":"2025-11-24 06:47:45","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":279322,"visible":true,"origin":"","legend":"\u003cp\u003eSurvey sites of the coastal forests in Niigata City, Japan. A) Location of the survey sites in Niigata Prefecture (black) and Niigata City (red), (B) The survey sites are divided into: Sites A to D and Sakata and Uwasekigata Parks surveyed for the distribution of \u003cem\u003eEupromus ruber i\u003c/em\u003enfestation, and Plot 1 and 2 for damage by \u003cem\u003eEupromus ruber \u003c/em\u003eand its oviposition characteristics.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8025870/v1/a6f13d315009bdf9597ae273.png"},{"id":96592822,"identity":"704bd1f8-ecb6-4c88-b9ba-8551d4ff3435","added_by":"auto","created_at":"2025-11-24 06:47:45","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":136902,"visible":true,"origin":"","legend":"\u003cp\u003eRelationship between diameter at breast height (DBH) of \u003cem\u003eMachilus thunbergii\u003c/em\u003e and tree height of oviposition scars by \u003cem\u003eEupromus ruber\u003c/em\u003e: oviposition sites categorized into trunk (brown) and branches (green).\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8025870/v1/6e026168c885dac6659ad4da.png"},{"id":102743102,"identity":"41f1e2cf-9adf-436d-9bc7-282420a21864","added_by":"auto","created_at":"2026-02-16 08:12:08","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":949730,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8025870/v1/88b33981-5c66-4d20-9359-cde7ef773d4b.pdf"},{"id":96592826,"identity":"32f04c8d-3861-489e-9a28-3453f4eac0e3","added_by":"auto","created_at":"2025-11-24 06:47:45","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":2377110,"visible":true,"origin":"","legend":"","description":"","filename":"FigSuppl.docx","url":"https://assets-eu.researchsquare.com/files/rs-8025870/v1/22d56a385b36c50c814dbff9.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Impacts of the pest wood-boring beetle, Eupromus ruber, on Lauraceae species in temperate coastal forests","fulltext":[{"header":"Key Messages","content":"\u003cp\u003eThe wood-boring beetle\u003cem\u003e\u0026nbsp;Eupromus ruber\u003c/em\u003e is expanding its distribution in temperate coastal forests along the Sea of Japan, affecting Lauraceae species. Field surveys show that taller, sun-exposed trees are preferentially oviposited, and beetle activity contributes to stem breakage and fungal invasion. Monitoring and integrated pest management are essential for forest conservation.\u003c/p\u003e"},{"header":"1. Introduction","content":"\u003cp\u003eCoastal forests serve as a protective buffer, safeguarding communities from wind-blown sand, strong winds, erosion, and tsunamis, thereby enhancing local resilience (Shepard et al. \u003cspan citationid=\"CR72\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Chang and Mori \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Zhu et al. \u003cspan citationid=\"CR93\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). In response to their ecological importance, global conservation and afforestation efforts have been initiated to preserve these ecosystems (Wu et al. \u003cspan citationid=\"CR86\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Xie et al. \u003cspan citationid=\"CR87\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Song et al. \u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). However, coastal forests are increasingly threatened by various stressors and disturbances, particularly invasive pests (Trumbore et al. \u003cspan citationid=\"CR81\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). The introduction of such species has been associated with severe declines in tree health across many coastal regions (Koch and Smith \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; Firmino et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Cobb et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). As biological invasions continue (Ramsfield et al. \u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Green et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), monitoring trends in invasive pest populations is necessary to protect the ecosystem services provided by coastal forests.\u003c/p\u003e\u003cp\u003eCoastal pine forests are widely distributed across East Asia (Han et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Bitog et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2011\u003c/span\u003e), and provide essential ecosystem services to coastal communities (Kusumoto et al. \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Torita et al. \u003cspan citationid=\"CR80\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Omori et al. \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). In Japan, however, these forests have been severely affected by pine wilt disease, caused by the pine wood nematode \u003cem\u003eBursaphelenchus xylophilus\u003c/em\u003e, which is thought to have been introduced from North America in the early 1900s (Mamiya \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e1988\u003c/span\u003e). The disease has contributed to the decline of coastal forests in Japan (Mamiya \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e1988\u003c/span\u003e; Teramoto and Shimokawa \u003cspan citationid=\"CR79\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). Once established, the nematode spreads rapidly through vector insects and human activity (Vicente et al. \u003cspan citationid=\"CR84\" class=\"CitationRef\"\u003e2012\u003c/span\u003e), making its management costly and challenging (Back et al. \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Historically, pine needle gathering was routinely practiced as a fuel resource in \u003cem\u003ePinus thunbergii\u003c/em\u003e coastal forests between the 1950s and 1960s, where it served as a household fuel resource (Konta \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2001\u003c/span\u003e). The decline of this practice following the transition to alternative fuels resulted in the accumulation of organic matter on the forest floor, which facilitated the invasion of broadleaf species (Konta \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2001\u003c/span\u003e). Reduced removal of fallen leaves and branches, coupled with broadleaf encroachment, further promoted nutrient accumulation in the soil (Fujita and Nakata \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2001\u003c/span\u003e). This nutrient enrichment has driven a gradual shift toward plantations dominated by native Lauraceae species, such as \u003cem\u003eMachilus thunbergii\u003c/em\u003e and \u003cem\u003eNeolitsea sericea\u003c/em\u003e, in place of pines that are better adapted to nutrient-poor soils (Fujita and Nakata \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2001\u003c/span\u003e; Yoneyama and Kamitani \u003cspan citationid=\"CR92\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). However, monoculture plantations remain vulnerable to pest and disease outbreaks compared with mixed-species forests (Jactel and Brockerhoff \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Jactel et al. \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Stemmelen et al. \u003cspan citationid=\"CR74\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Supporting this, European studies have shown that tree species richness at the plot or stand scale is negatively correlated with the abundance of invasive forest pests (Jactel et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Guyot et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2015\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eIn recent years, cases of invasive wood-boring beetles overcoming biogeographical barriers and successfully establishing their populations have been reported worldwide (Garonna et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Horrocks et al. \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). The wood-boring beetle \u003cem\u003eEupromus ruber\u003c/em\u003e is widely distributed in East Asia (Lim et al. \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2013\u003c/span\u003e) and infests Lauraceae trees. Adult beetles feed on the branches and leaves of these trees (Kojima and Hayashi \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e1969\u003c/span\u003e; Hayashi et al. \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e1984\u003c/span\u003e). In the warm-temperate zones of Japan, \u003cem\u003eE. ruber\u003c/em\u003e has been reported to infest Lauraceae trees (Kojima and Hayashi \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e1969\u003c/span\u003e). The larvae of this species bore into the cambial layer of young trunks and branches of host trees and damage the cambium (Kojima \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e1931\u003c/span\u003e; Banno and Yamagami \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e1989\u003c/span\u003e). Although \u003cem\u003eE. ruber\u003c/em\u003e infestation typically does not result in the death of Lauraceae species (Banno and Yamagami \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e1989\u003c/span\u003e), severe damage has been observed in Lauraceae trees planted as street trees (Ohga et al. \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e1995\u003c/span\u003e). These infestations, which affect healthy parts of the tree, can facilitate fungal invasions (Ohga et al. \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e1995\u003c/span\u003e). Furthermore, Lauraceae species planted in coastal forests have shown signs of branch and trunk breakage due to \u003cem\u003eE. ruber\u003c/em\u003e infestation (Sugimoto and Yamada \u003cspan citationid=\"CR75\" class=\"CitationRef\"\u003e2007\u003c/span\u003e). In coastal areas with heavy winter snowfall, there is concern that Lauraceae species infested by \u003cem\u003eE. ruber\u003c/em\u003e may experience additional physical damage from the weight of accumulated snow.\u003c/p\u003e\u003cp\u003eThis study investigated pest damage critical for the maintenance and management of coastal forests dominated by evergreen broadleaf trees of Lauraceae, with the goal of developing effective pest management strategies. Specifically, we: 1) identified the damage caused by the pest species \u003cem\u003eE. ruber\u003c/em\u003e to Lauraceae trees in coastal forests and examined the pest\u0026rsquo;s oviposition site preferences, and 2) provided recommendations for pest control measures to mitigate damage in these coastal forests. The introduction should open to a few explicit working hypotheses or at least a few explicit research questions; if none is available, the manuscript may be directly returned to the authors.\u003c/p\u003e"},{"header":"2. Material and methods","content":"\u003cp\u003eChoose your number of sections as appropriate.\u003c/p\u003e\n\u003cp\u003e2.1 Study area\u003c/p\u003e\n\u003cp\u003eThe study was conducted in 2011 and 2012 in the coastal forests of Niigata City, located in central Japan. The mean annual temperature and precipitation recorded between 1980 and 2020 in the study area were 13.9 \u0026deg;C and 1825.9 mm, respectively (Japan Meteorological Agency 2024). The region experiences heavy snowfall, with a mean annual maximum recorded snow depth of 35.8 cm during the same period (Japan Meteorological Agency, 2024). The distribution of \u003cem\u003eE. ruber\u003c/em\u003e is limited to areas west of Tokyo on the Pacific side and west of Ishikawa Prefecture along the Sea of Japan coast in Japan, and it was not recorded in Niigata City until the early 2000s (Ministry of Agriculture, Forestry and Fisheries 1998; Ohbayashi and Niisato 2007). However, Lauraceae trees, including \u003cem\u003eM. thunbergii\u003c/em\u003e and N. sericea, have been repeatedly planted in the coastal forests of Niigata City (Koda 2004; Takeda and Kaneko 2007). It is highly probable that \u003cem\u003eE. ruber\u003c/em\u003e invaded the area through this process as an alien species.\u003c/p\u003e\n\u003cp\u003e2.2 Distribution of tree damage caused by\u003cem\u003e\u0026nbsp;E. ruber\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eWe first conducted a survey from May to October 2011 to determine the distribution of \u003cem\u003eE. ruber\u003c/em\u003e by examining its host tree, \u003cem\u003eM. thunbergii\u003c/em\u003e, for signs of damage. The primary aim was to determine the extent of the beetle\u0026rsquo;s range expansion from the coastal forests at the foothills of Mt. Kakuda, where it had first been confirmed. The survey area stretched along a coastal forest zone from Mt. Kakuda (37.7976\u0026deg;N, 138.8263\u0026deg;E) to Sekiya (37.9214\u0026deg;N, 139.0279\u0026deg;E) (Fig. 1), and was divided into four sites, labeled Site A to Site D, to allow for a systematic assessment of the beetle\u0026rsquo;s range expansion along the coastline. In addition, we investigated \u003cem\u003eE. ruber\u003c/em\u003e occurrence in Sakata Park (37.8189\u0026deg;N, 138.8799\u0026deg;E) and Uwasekigata Park (37.7908\u0026deg;N, 138.8664\u0026deg;E), where \u003cem\u003eM. thunbergii\u003c/em\u003e trees have been planted in urban parks adjacent to the coastal forest. These parks were selected simply to document the distribution of E. ruber within the city area.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eMachilus thunbergii\u003c/em\u003e grows vigorously in relatively open areas, primarily regenerating in gaps and along forest edges (Yamamoto, 1992; Takyu \u0026amp; Ohsawa, 1997; Takyu, 1998; Yamagawa et al., 2007). We surveyed \u003cem\u003eM. thunbergii\u003c/em\u003e trees located along forest edges by cycling along the road that runs through Sites A to D. In addition, in parks within Sites C and D, as well as in Sakata Park and Uwasekigata Park, where walking trails were available, we walked along the trails to search for \u003cem\u003eM. thunbergii\u003c/em\u003e trees along the forest edges. \u003cem\u003eE. ruber\u003c/em\u003e produces distinctive elliptical oviposition scars by peeling the bark (Appendix Fig. 1A). Its larvae expel frass through fecal discharge holes, and newly emerged adults exit the tree through 7\u0026ndash;8 mm diameter exit holes (Appendix Fig. 1B, C) (Kojima \u0026amp; Hayashi, 1969). In Japan, \u003cem\u003eE. ruber\u003c/em\u003e is the only insect known to leave such distinctive signs on living Lauraceae trees (Kojima \u0026amp; Hayashi, 1969; Ministry of Agriculture, Forestry and Fisheries, 1998; Ohbayashi \u0026amp; Niisato, 2007).\u003c/p\u003e\n\u003cp\u003eUpon visually identifying \u003cem\u003eM. thunbergii\u003c/em\u003e trees, we approached them to closely inspect for these signs of damage. Trees showing such signs were recorded as part of the beetle\u0026rsquo;s distribution. For tall \u003cem\u003eM. thunbergii\u003c/em\u003e trees, we climbed the trees directly to check for damage.\u003c/p\u003e\n\u003cp\u003e2.3 Damage Assessment of Lauraceae Species by \u003cem\u003eE. ruber\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eFrom August to October 2012, we surveyed the damage and oviposition patterns of \u003cem\u003eE. ruber\u003c/em\u003e in the coastal forests at the foothills of Mt. Kakuda. This forest stand was selected because \u003cem\u003eE. ruber\u003c/em\u003e invasion had been confirmed in the area, and vegetation succession appeared to be progressing following pine wilt disease, with species of the family Lauraceae particularly \u003cem\u003eM. thunbergii\u003c/em\u003e and \u003cem\u003eN. sericea\u003c/em\u003e regenerating and becoming increasingly dominant. The forest stand is divided by a road into a seaward stand (Plot 1) and an inland stand (Plot 2) (Fig. 1). Plot 1, with a maximum forest belt width of about 270 m and a total area of approximately 11.8 ha, underwent thinning around two years ago. The stand is primarily composed of \u003cem\u003ePinus thunbergia\u0026nbsp;\u003c/em\u003e(Pinaceae), with few other tree species. Deciduous broadleaf species such as \u003cem\u003eCerasus\u003c/em\u003e spp. (Rosaceae) and \u003cem\u003eZelkova serrata\u003c/em\u003e (Ulmaceae) are rare. Most of the \u003cem\u003eM. thunbergii\u003c/em\u003e and \u003cem\u003eN. sericea\u0026nbsp;\u003c/em\u003e(both Lauraceae) trees are coppice regeneration shoots following thinning, with tree heights mostly under 3 m. Plot 2 has a maximum forest belt width of about 130 m and a total area of around 4.9 ha. This stand is a mixed multilayer forest, with a canopy dominated by \u003cem\u003eP. thunbergii\u003c/em\u003e, a subcanopy layer comprising Acer pictum (Sapindaceae), \u003cem\u003eQuercus serrata\u003c/em\u003e (Fagaceae), Lauraceae species \u003cem\u003eM. thunbergii\u003c/em\u003e, and \u003cem\u003eN. sericea\u003c/em\u003e, and an understory dominated by \u003cem\u003eViburnum dilatatum\u003c/em\u003e (Viburnaceae) and \u003cem\u003eMorus australis\u003c/em\u003e (Moraceae).\u003c/p\u003e\n\u003cp\u003eIn these plots, we surveyed all Lauraceae species, including \u003cem\u003eM. thunbergii\u003c/em\u003e, that were at least 1.3 m tall to assess damage caused by \u003cem\u003eE. ruber\u003c/em\u003e. For all surveyed Lauraceae species, we measured the diameter at breast height (DBH) and climbed taller trees to inspect higher sections directly. Additionally, for \u003cem\u003eM. thunbergii\u003c/em\u003e, we recorded tree height, tree position, the number of oviposition scars, and the height and diameter of these scars. The study area consisted of two plots differing in management status: Plot 1 (thinned area) and Plot 2 (unthinned area). Each plot contained forest edges (trees within five meters of the forest boundary or road) and forest interiors (trees farther inside the forest). Tree positions were classified based on their location as either forest edge or forest interior. Oviposition scars were counted, with a focus on newer scars likely made in the current year. These newer scars were identified by the absence of discoloration on the scraped area and the lack of bark regeneration or swelling around the scar. To measure oviposition height, one researcher held a measuring pole from the ground while another climbed the tree to confirm its position. The diameter of the tree at the oviposition site was measured with calipers within the accessible range.\u003c/p\u003e\n\u003cp\u003eAdditional data on solar radiation and crown base height were recorded for \u003cem\u003eM. thunbergii\u0026nbsp;\u003c/em\u003etrees taller than 3 m. In September 2012, we measured solar radiation using a photon meter (Digital Ohm Co. Ltd: HD230.2) to assess the photosynthetic photon flux density (PPFD). To calculate the relative photosynthetic photon flux density (rPPFD), measurements were taken three times each at a standardized height of 1.8 m at four evenly spaced points around each tree, with simultaneous measurements on bare ground. The relative photosynthetic photon flux density for each point was calculated and averaged. The crown length was determined by subtracting the crown base height from the total tree height, and the crown ratio (%) was calculated as the crown length divided by the total tree height.\u003c/p\u003e\n\u003cp\u003e2.4 Host tree damage\u003c/p\u003e\n\u003cp\u003eDuring the surveys in Plot 1 and Plot 2, we assessed \u003cem\u003eM. thunbergii\u003c/em\u003e trees over 3 m in height for bole breakage, dieback, and the presence of fungal fruiting bodies. To examine the effects of \u003cem\u003eE. ruber\u003c/em\u003e on bole breakage and dieback, we recorded the extent of damage at break points caused by \u003cem\u003eE. ruber\u003c/em\u003e and assessed trunk damage due to its infestation. For \u003cem\u003eM. thunbergii\u003c/em\u003e trees with confirmed bole breakage, we measured the length of the broken bole from the base to the break point and from the break point to the broken tip to estimate the tree\u0026rsquo;s original height before breakage.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe extent of \u003cem\u003eE. ruber\u003c/em\u003e-related damage at break points was determined by checking for oviposition scars and boring marks. To assess fungal invasion associated with \u003cem\u003eE. ruber\u003c/em\u003e infestation, we recorded the presence of fungal fruiting bodies, oviposition scars, and boring marks in areas where fungi were found. For trees showing dieback, we also recorded cracks, pressure marks, and any signs of \u003cem\u003eE. ruber\u003c/em\u003e damage.\u003c/p\u003e\n\u003cp\u003eThe level of \u003cem\u003eE. ruber\u003c/em\u003e-induced damage was assessed on the trunk below the crown base. The damage extent was evaluated based on the continuous oviposition scars, fecal discharge holes, and adult emergence holes of \u003cem\u003eE. ruber\u0026nbsp;\u003c/em\u003ealong the trunk in relation to unaffected areas. \u003cem\u003eEupromus ruber\u003c/em\u003e larvae hatch from oviposition scars and create fecal discharge holes at various points along the tunnel when boring into the tree. These fecal discharge holes, along with adult emergence holes, contribute to continuous damage. Damage levels were classified into five categories based on the percentage of affected trunk area: Level 1 (0%), Level 2 (less than 5%), Level 3 (5\u0026ndash;15%), Level 4 (15\u0026ndash;30%), and Level 5 (more than 30%).\u003c/p\u003e\n\u003cp\u003e2.5 Statistical analysis\u003c/p\u003e\n\u003cp\u003eWe used a generalized linear model (GLM) with a Poisson error distribution to examine the factors influencing the number of \u003cem\u003eE. ruber\u003c/em\u003e oviposition scars. The analysis focused on \u003cem\u003eM. thunbergii\u003c/em\u003e trees taller than 3 m, with the number of oviposition scars as the response variable. Explanatory variables included tree height, crown ratio (%), relative photosynthetic photon flux density (rPPFD, %), tree location (edge vs. interior forest), and management status (thinned vs. unthinned plots).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAdditionally, we applied logistic regression to explore the factors influencing bole breakage in \u003cem\u003eM. thunbergii\u003c/em\u003e trees. This analysis also focused on trees taller than 3 m, using the presence or absence of bole breakage (1 = breakage, 0 = no breakage) as the response variable. Explanatory variables included \u003cem\u003eE. ruber\u003c/em\u003e-induced damage level, tree height, rPPFD, tree location, and management status.\u003c/p\u003e\n\u003cp\u003eTo address potential multicollinearity among explanatory variables, we calculated the Variance Inflation Factor (VIF) and excluded variables with VIF \u0026ge; 5 to ensure all retained variables remained below this threshold (Akinwande 2015). We then constructed multiple GLMs and logistic regression models, testing all possible combinations of explanatory variables. The optimal model was selected using a stepwise method based on the Akaike Information Criterion (AIC) (Lander 2013). Our analyses included only main effects, without interaction terms. All statistical analyses were conducted using R 2.14.0 (R Core Team 2012).\u003c/p\u003e"},{"header":"3. Results","content":"\u003cp\u003e3.1 Distribution of \u003cem\u003eE. ruber\u0026nbsp;\u003c/em\u003eat the Study Sites\u003c/p\u003e\n\u003cp\u003eThe survey identified\u003cem\u003e\u0026nbsp;\u003c/em\u003esigns of \u003cem\u003eE. ruber\u003c/em\u003e activity (e.g., oviposition scars and larval boring)\u003cem\u003e\u0026nbsp;\u003c/em\u003ein Site A, Sakata Park, and Uwasekigata Park. However, no signs of the beetle were found in Site B, where only small \u003cem\u003eM. thunbergii\u0026nbsp;\u003c/em\u003esaplings were observed. Although \u003cem\u003eM. thunbergii\u003c/em\u003e trees were found in Sites C and D, no evidence of \u003cem\u003eE. ruber\u003c/em\u003e-induced damage\u003cem\u003e\u0026nbsp;\u003c/em\u003ewas recorded.\u003c/p\u003e\n\u003cp\u003e3.2 Damage by \u003cem\u003eE. ruber\u003c/em\u003e in Lauraceae Species\u003c/p\u003e\n\u003cp\u003eAcross Plot 1 and Plot 2, a total of 401 Lauraceae trees were surveyed, comprising \u003cem\u003eM. thunbergii\u003c/em\u003e (253 trees), \u003cem\u003eNeolitsea sericea\u003c/em\u003e (146 trees), \u003cem\u003eCinnamomum japonicum\u003c/em\u003e (1 tree), and \u003cem\u003eLaurus nobilis\u003c/em\u003e (1 tree). Damage caused by \u003cem\u003eE. ruber\u003c/em\u003e, including oviposition scars, frass discharge holes, and expelled frass, was observed on 128 out of 253 \u003cem\u003eM. thunbergii\u003c/em\u003e trees and on the single \u003cem\u003eC. japonicum\u003c/em\u003e tree. No signs of damage were detected on \u003cem\u003eN. sericea\u003c/em\u003e or \u003cem\u003eL. nobilis\u003c/em\u003e (Appendix Fig. 2A, B). Among \u003cem\u003eM. thunbergii\u003c/em\u003e, the damage was observed even in trees with a DBH of less than 5 cm, and all \u003cem\u003eM. thunbergii\u003c/em\u003e and \u003cem\u003eC. japonicum\u003c/em\u003e trees with a DBH of 5 cm or more were affected by\u003cem\u003e\u0026nbsp;E. ruber\u0026nbsp;\u003c/em\u003e(Appendix Fig. 2C, D). In contrast, \u003cem\u003eN. sericea\u003c/em\u003e trees, ranging from less than 5 cm to nearly 35 cm DBH, showed no signs of infestation. Similarly, the single \u003cem\u003eL. nobilis\u003c/em\u003e tree, with a DBH under 5 cm, remained undamaged.\u003c/p\u003e\n\u003cp\u003e3.3 Oviposition by \u003cem\u003eE. ruber\u0026nbsp;\u003c/em\u003eand Environmental Factors in Plots 1 and 2\u003c/p\u003e\n\u003cp\u003eGLM analysis (Table 1) revealed that the number of \u003cem\u003eE. ruber\u003c/em\u003e oviposition scars was significantly influenced by tree height (Coefficient = 0.36, p \u0026lt; 0.001), crown ratio (Coefficient = 0.02, p \u0026lt; 0.01), and rPPFD (Coefficient = 0.03, p \u0026lt; 0.001). Additionally, trees located at forest edges exhibited significantly higher oviposition scars (E = 0.52, p \u0026lt; 0.01).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe height of oviposition points was strongly positively correlated with tree DBH (Spearman\u0026rsquo;s r = 0.796, p \u0026lt; 0.001), indicating a shift in oviposition preference from trunks to branches as trees grow larger (Fig. 2). Oviposition activity was most frequently observed on surfaces with a diameter of 2\u0026ndash;4 cm, including both branches and trunks, with no activity observed on surfaces larger than 8 cm in diameter (Appendix Fig. 3).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1\u003c/strong\u003e A generalized linear model with the number of oviposition scars as the dependent variable (response variable) in the final model.\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003eVariables\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003eEstimate\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003eStd. Error\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003et value\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003ep value\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003eIntercept\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e-2.48\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e0.39\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e0.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e***\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003eTree height\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e0.36\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e0.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e0.18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e***\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003eCrown ratio\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e0.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e**\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003erPPFD (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e0.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e***\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003eForest edge\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e0.52\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e0.18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e0.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e**\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e***: p\u0026lt;0.001, **: p\u0026lt;0.01, *: p\u0026lt;0.05\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;Among 138 \u003cem\u003eM. thunbergii\u003c/em\u003e trees taller than 3 m, 110 (79.7%) were healthy, 27 (19.6%) exhibited bole breakage, and one (0.7%) was dead. Fruiting bodies of Pleurotaceae fungi were found on five non-broken trees, emerging from oviposition scars or exit holes created by \u003cem\u003eE. ruber\u003c/em\u003e (Appendix Fig. 4A, B). All trees with bole breakage showed evidence of \u003cem\u003eE. ruber\u003c/em\u003e damage, with both oviposition scars and boring marks present on 92.6% of damaged areas, while 7.4% had only boring marks (Appendix Fig. 4C, D, Appendix Fig. 5).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eLogistic regression analysis (Table 2) revealed that bole breakage was significantly positively associated with the extent of \u003cem\u003eE. ruber\u003c/em\u003e damage (Coefficient = 0.78, p \u0026lt; 0.01) and rPPFD (Coefficient = 0.05, p \u0026lt; 0.01), while tree height had a significantly negative association (Coefficient = \u0026minus;0.6, p \u0026lt; 0.01). Although not statistically significant, trees located at forest edges tended to have higher rates of bole breakage compared to those located in the interior of the forest. The single dead tree observed in this study showed no signs of suppression damage or injury other than perforations caused by \u003cem\u003eE. ruber\u003c/em\u003e larvae.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 2\u003c/strong\u003e The final model of logistic regression analysis with the presence or absence of broken trunk in \u003cem\u003eMachilus thunbergii\u003c/em\u003e as the dependent variable.\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003eVariables\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003eEstimate\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003eStandard Error\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003et value\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003ep value\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003eIntercept\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e-2.92\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e1.34\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e0.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e***\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003eDamage level of \u003cem\u003eEupromus ruber\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20%;\"\u003e\n \u003cp\u003e0.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20%;\"\u003e\n \u003cp\u003e0.26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20%;\"\u003e\n \u003cp\u003e2.07\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 20%;\"\u003e\n \u003cp\u003e**\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003eTree height\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e-0.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e0.23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e-2.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e**\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003erPPFD (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e0.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e1.69\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e**\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003eForest edge\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e0.81\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e0.57\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003e0.92\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 20%;\"\u003e\n \u003cp\u003en.s.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e***: p\u0026lt;0.001, **: p\u0026lt;0.01, *: p\u0026lt;0.05, n.s.: p\u003cu\u003e\u0026gt;\u003c/u\u003e0.05\u003c/p\u003e"},{"header":"4. Discussion","content":"\u003cp\u003e4.1 Factors affecting bole damage by \u003cem\u003eE. ruber\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThis study confirmed \u003cem\u003eE. ruber\u0026nbsp;\u003c/em\u003eoccurrence in Site A, Sakata Park, and Uwasekigata Park within Niigata City. However, it was not found in Site B, C, or D, indicating that at the time of the survey (2011 and 2012), its distribution remained localized and had not yet spread throughout the coastal forests of Niigata City. This suggests that the invasion of \u003cem\u003eE. ruber\u003c/em\u003e is still in its early stages. The larvae of \u003cem\u003eE. ruber\u003c/em\u003e primarily infest \u003cem\u003eM. thunbergii\u003c/em\u003e, although they may occasionally bore into living \u003cem\u003eCinnamomum japonicum\u003c/em\u003e and \u003cem\u003eMachilus japonica\u003c/em\u003e under rare conditions in Japan\u0026rsquo;s warm-temperate zones (Kojima and Hayashi 1969). In this study, signs of \u003cem\u003eE. ruber\u003c/em\u003e oviposition and boring were observed in \u003cem\u003eM. thunbergii\u003c/em\u003e (128 of 253 trees) and \u003cem\u003eC. japonicum\u0026nbsp;\u003c/em\u003e(1 of 1 tree), confirming that \u003cem\u003eM. thunbergii\u003c/em\u003e is the primary host at the study site. In contrast, despite the broad size range of \u003cem\u003eNeolitsea sericea\u003c/em\u003e trees surveyed, no signs of infestation were detected, suggesting that \u003cem\u003eN. sericea\u003c/em\u003e is not a preferred host for oviposition. All \u003cem\u003eM. thunbergii\u003c/em\u003e trees with a DBH greater than 5 cm exhibited signs of \u003cem\u003eE. ruber\u003c/em\u003e damage, including oviposition scars and larval boring, consistent with observations from other warm-temperate habitats, where few trees show no signs of damage (Kojima and Hayashi 1969). Additionally, some \u003cem\u003eM. thunbergii\u003c/em\u003e trees with a DBH smaller than 5 cm also showed signs of infestation, suggesting that eggs or larvae may already be present in relatively small trees.\u003c/p\u003e\n\u003cp\u003e4.2 Substrate Diameter and Oviposition Preferences\u003c/p\u003e\n\u003cp\u003eMany species within the Cerambycidae family exhibit oviposition preferences based on substrate diameter (e.g. Morewood et al. 2003a; Lee and Lee, 2020; Turgeon et al. 2024). Similarly, \u003cem\u003eE. ruber\u003c/em\u003e is thought to select oviposition sites based on branch diameter (Kojima and Hayashi 1969; Sugimoto and Yamada 2007). In this study, oviposition scars were found on both branches and boles, with oviposition points shifting from boles to branches as trees grew taller. Despite this shift, the substrate diameter at oviposition points remained concentrated between 2 and 4 cm, suggesting that diameter is a more critical factor than wood type or substrate height. This preference likely reflects a trade-off between the difficulty of penetrating bark and the availability of resources for larval development.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eBark serves as a protective barrier for plant boles and branches (Ferrenberg and Mitton 2014; Rosell et al. 2016), and thicker bark\u0026mdash;more common in larger-diameter substrates\u0026mdash;poses higher energy costs for oviposition and may increase predation risk (Edwards and Linit, 1991; Rosell et al. 2016). Conversely, thinner branches, while easier to penetrate, offer fewer resources for larvae, potentially increasing mortality due to competition (Coulson 1979; Rice 1989; Hanks et al. 1991). Since \u003cem\u003eE. ruber\u003c/em\u003e lays only 5\u0026ndash;10 eggs per oviposition point (Kojima and Hayashi, 1969), selecting substrates of optimal diameter is essential for minimizing larval competition and improving survival rates.\u003c/p\u003e\n\u003cp\u003eThe observed resource preference may also be influenced by the scarcity of suitable oviposition sites resulting from the rapid growth of the \u003cem\u003eE. ruber\u003c/em\u003e population. Invasive species often experience population surges in non-native ranges due to the absence of natural enemies and high host susceptibility (Wolfe et al. 2002; Brockerhoff and Liebhold 2017). The presence of numerous old oviposition scars in the study area suggests a rapid population increase, with branches and boles of suitable diameters already heavily utilized. Similar to other wood-boring beetles, such as \u003cem\u003eMonochamus alternatus\u003c/em\u003e and \u003cem\u003eM. scutellatus\u003c/em\u003e, which avoid previously used substrates to reduce intraspecific competition (Anbutsu and Togashi 1996, 2002; Peddle et al. 2002), \u003cem\u003eE. ruber\u003c/em\u003e may have shifted to thinner, unused branches to mitigate competition in this study area.\u003c/p\u003e\n\u003cp\u003e4.3 Other Environmental Factors Affecting Oviposition Preferences\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eE. ruber\u003c/em\u003e exhibited a preference for oviposition on \u003cem\u003eM. thunbergii\u003c/em\u003e trees with greater height, higher crown ratios, higher rPPFD values, and those located at forest edges. Taller trees with higher crown ratios provide more branches of suitable diameter, increasing the availability of oviposition sites and potentially enhancing offspring survival by offering better protection from parasites, desiccation, and extreme weather conditions (Paulino-Neto et al. 2005). The preference for trees with higher rPPFD values may be explained by \u003cem\u003eE. ruber\u003c/em\u003e\u0026rsquo;s positive phototaxis. Similar patterns have been observed in other wood-boring insects, which frequently oviposit on trees in well-lit environments (C\u0026aacute;rdenas and Gallardo 2013; Kautz et al. 2013; Ka\u0026scaron;\u0026aacute;k and Foit 2018). Additionally, \u003cem\u003eM. thunbergii\u003c/em\u003e thrives in such conditions, regenerating primarily in forest gaps (Yamamoto 1992; Takyu and Ohsawa 1997; Takyu 1998; Yamagawa et al. 2007). Another wood-boring species, \u003cem\u003eAnoplophora glabripennis\u003c/em\u003e, has been shown to utilize visual cues, particularly when adult beetles search for host plants from a distance (Lyu et al. 2023). Similarly, \u003cem\u003eE. ruber\u003c/em\u003e may rely on visual cues to locate host trees in brighter environments, where reduced tree density enhances visibility. Furthermore, higher wood temperatures in sunlit areas may accelerate larval development, as reported in other wood-boring beetles (Graham 1925; Savely 1939). These factors collectively suggest that \u003cem\u003eE. ruber\u003c/em\u003e selects trees in brighter environments or at forest edges to optimize offspring fitness.\u003c/p\u003e\n\u003cp\u003e4.4 Boles Damage and Associated Risks\u003c/p\u003e\n\u003cp\u003eInfestation by wood-boring insects like \u003cem\u003eE. ruber\u003c/em\u003e often leads to structural damage, including decay fungi invasion, branch drop, bole breakage, and, in severe cases, tree mortality (Sharifi et al. 1970; Nowak et al. 2001; Negussie et al. 2018; Monteys et al. 2021). In this study, 19.6% of surveyed \u003cem\u003eM. thunbergii\u003c/em\u003e trees taller than 3 m exhibited bole breakage, and all cases were associated with \u003cem\u003eE. ruber\u003c/em\u003e damage, as evidenced by oviposition scars or boring marks at the break points. Logistic regression analysis confirmed a positive relationship between the extent of \u003cem\u003eE. ruber\u003c/em\u003e damage and the likelihood of bole breakage.\u003c/p\u003e\n\u003cp\u003eBefore reaching maturity, \u003cem\u003eE. ruber\u003c/em\u003e larvae consume between 7 and 17 g of dry wood mass or between 12 and 33 cm\u0026sup3; in volume (Banno \u0026amp; Yamagami 1989). Their boring activity weakens the structural integrity of trees by forming cavities, an effect exacerbated by larval aggregation around oviposition sites (Sugimoto and Yamada 2007). Additionally, wood-boring beetle damage promotes the invasion of decay fungi (Ohga et al. 1995; Panzavolta et al. 2018; Linnakoski and Forbes 2019), which can lead to bole and root rot, thereby increasing the risk of tree collapse (Ding et al. 2020). In this study, Pleurotaceae fungi were frequently observed at \u003cem\u003eE. ruber\u003c/em\u003e oviposition scars (Appendix Fig. 4B), highlighting the beetle\u0026rsquo;s role in facilitating fungal colonization and subsequent bole decay.\u003c/p\u003e\n\u003cp\u003eThe observed bole breakage rate (19.6%) was substantially higher than the 2.7% reported in other coastal forests affected by \u003cem\u003eE. ruber\u003c/em\u003e (Sugimoto and Yamada 2007). This discrepancy may be attributed to the greater snowfall intensity at the study site, where the average maximum snow depth (35.8 cm, 1980\u0026ndash;2020) was nearly eight times higher than that recorded in Sugimoto and Yamada\u0026rsquo;s study (4.3 cm, 1980\u0026ndash;2020) (Japan Meteorological Agency, 2024). Evergreen broadleaf trees, such as \u003cem\u003eM. thunbergii\u003c/em\u003e, retain their foliage in winter, making them more susceptible to snow accumulation and stem breakage (Givnish 2002; Chen and Sun 2010). The study area recorded a maximum snow depth of 81 cm in 2010 (Japan Meteorological Agency 2024), suggesting that trees weakened by \u003cem\u003eE. ruber\u003c/em\u003e infestation may have sustained further damage due to heavy snow loads, resulting in increased bole breakage that year.\u003c/p\u003e\n\u003cp\u003e4.5 Tree Mortality Caused by\u003cem\u003e\u0026nbsp;E. ruber\u003c/em\u003e Infestation\u003c/p\u003e\n\u003cp\u003ePrevious studies suggest that \u003cem\u003eM. thunbergii\u003c/em\u003e generally does not die solely from \u003cem\u003eE. ruber\u003c/em\u003e damage (Banno and Yamagami 1989). In this study, only one dead \u003cem\u003eM. thunbergii\u003c/em\u003e tree was observed, indicating that mortality due to \u003cem\u003eE. ruber\u003c/em\u003e infestation alone is unlikely. However, for smaller-diameter trees, mortality may result from cumulative weakening caused by boring, bole breakage, or other forms of structural damage (Sugimoto and Yamada 2007). In certain longhorn beetles, such as \u003cem\u003eAnoplophora glabripennis\u003c/em\u003e and \u003cem\u003eAromia bungii\u003c/em\u003e, larval boring into the cambium or wood can directly lead to tree death (Morewood et al. 2003b; Urano et al. 2022).\u003c/p\u003e\n\u003cp\u003e4.6 Pest Management in Coastal Forests\u003c/p\u003e\n\u003cp\u003eThis study demonstrated that \u003cem\u003eE. ruber\u003c/em\u003e infestation in coastal forests leads to bole breakage in \u003cem\u003eM. thunbergii\u003c/em\u003e, with damage exacerbated in regions with heavy snowfall. \u003cem\u003eM. thunbergii\u003c/em\u003e has been planted in coastal forests even beyond the natural range of \u003cem\u003eE. ruber\u003c/em\u003e (Nobori et al. 2004; Nitta and Kaneko, 2023), raising concerns that these cultivated trees may facilitate the beetle\u0026rsquo;s range expansion. To mitigate this risk, precautions should be taken to prevent the anthropogenic introduction of \u003cem\u003eE. ruber\u003c/em\u003e into new areas.\u003c/p\u003e\n\u003cp\u003eThe study also revealed that \u003cem\u003eE. ruber\u003c/em\u003e larvae can penetrate the interior of relatively small \u003cem\u003eM. thunbergii\u003c/em\u003e trees with a DBH of less than 5 cm. Oviposition scars were observed on branches as thin as 2 cm in diameter (Kojima and Hayashi 1969). Therefore, thorough inspections for oviposition scars are essential when introducing \u003cem\u003eM. thunbergii\u003c/em\u003e and \u003cem\u003eC. japonicum\u003c/em\u003e to coastal forests. In contrast, \u003cem\u003eN. sericea\u003c/em\u003e showed no signs of damage from \u003cem\u003eE. ruber\u003c/em\u003e in the study area.\u003c/p\u003e\n\u003cp\u003eAdditionally, tall evergreen species, such as \u003cem\u003eIlex integra\u003c/em\u003e and \u003cem\u003eTernstroemia gymnanthera\u003c/em\u003e, which are expected to contribute to the diversity of coastal forests (Yamaguchi and Nakata 2008), may play a role in reducing pest impacts. Forests with higher tree species diversity are generally less susceptible to pest and disease outbreaks (Jactel and Brockerhoff 2007; Stemmelen et al. 2023; Field et al. 2025). Thus, promoting species diversity and selecting species adapted to local environments, rather than relying on monocultures, can help mitigate the risks posed by pests like \u003cem\u003eE. ruber\u003c/em\u003e.\u003c/p\u003e\n\u003cp\u003eThe severity of pest damage varies according to species-specific traits and microclimatic conditions, highlighting the importance of understanding these factors to improve pest control efficiency (Naves et al. 2006; Mazaheri et al. 2011; Kautz et al. 2013; Jonsson et al. 2015; Mari\u0026ntilde;o et al. 2016). In coastal forests already invaded by \u003cem\u003eE. ruber\u003c/em\u003e, control efforts should focus on host trees, particularly \u003cem\u003eM. thunbergii\u003c/em\u003e and \u003cem\u003eC. japonicum\u003c/em\u003e. This study revealed that \u003cem\u003eE. ruber\u003c/em\u003e prefers oviposition sites on \u003cem\u003eM. thunbergii\u003c/em\u003e located in bright areas or at forest edges. Therefore, control measures should prioritize these areas, as well as isolated trees and those in canopy gaps caused by pine wilt disease.\u003c/p\u003e\n\u003cp\u003ePhysical control methods, such as wrapping tree trunks with netting, can prevent wood-boring beetles like\u003cem\u003e\u0026nbsp;E. ruber\u003c/em\u003e from boring and laying eggs (Kain et al. 2010; Ranger et al. 2019; Yamamoto et al. 2024). Covering trunks with plastic or burlap is particularly effective for young \u003cem\u003eM. thunbergii\u003c/em\u003e trees, preventing boles and branches from breaking caused by oviposition. Early application and removal of branches with oviposition scars are recommended to eliminate eggs and larvae.\u003c/p\u003e\n\u003cp\u003eThis study also found that oviposition was concentrated on trees with a high crown ratio. Increasing tree density in coastal forests to promote early dieback of lower branches or conducting selective pruning may reduce oviposition damage. However, these practices could increase the height-to-diameter ratio of trees, making them more vulnerable to wind and snow damage. Therefore, pest management strategies should strike a balance between the risks of \u003cem\u003eE. ruber\u003c/em\u003e infestation and the structural stability of trees, and regular monitoring is essential to adapt management practices accordingly.\u003c/p\u003e"},{"header":"5. Conclusion","content":"\u003cp\u003eThis study revealed that \u003cem\u003eE. ruber\u003c/em\u003e infestation causes significant bole damage in \u003cem\u003eM. thunbergii\u003c/em\u003e within coastal forests, particularly in regions with heavy snowfall, where weakened stems are more prone to breakage. Since \u003cem\u003eM. thunbergii\u003c/em\u003e has been widely planted beyond the beetle\u0026rsquo;s natural range, careful management is required to prevent further spread. Regular inspections for oviposition scars, especially on thin branches, and early removal of infested parts are crucial to limit damage. Increasing tree species diversity, adjusting stand density, and prioritizing monitoring in bright or edge environments where \u003cem\u003eE. ruber\u003c/em\u003e is most active can reduce infestation risks. Integrated pest management strategies balancing pest control and forest stability are essential for the long-term conservation and restoration of coastal forests.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eConceptualization: RA, MN; Methodology: RA, MN; Formal analysis and investigation: RA; Writing \u0026ndash; original draft preparation: RA; Writing \u0026ndash; review and editing: MN, AN, TY; Funding acquisition: MN; Resources: MN; Supervision: MN, TY.The authors read and approved the final manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eWe would like to express our gratitude to Dr. Shota Deguchi and Mr. Daisuke Ataka for their collaboration in this study.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAkinwande MO, Dikko HG, Samson A (2015) Variance inflation factor: As a condition for the inclusion of suppressor variable (s) in regression analysis. 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Ocean \u0026amp; Coastal Management 254: 107190. https://doi.org/10.1016/j.ocecoaman.2024.107190\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Cerambycidae, Forest damage prevention, Forest management, Invasion biology, Tree breakage, Wood-boring pests","lastPublishedDoi":"10.21203/rs.3.rs-8025870/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8025870/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cem\u003e\u003cstrong\u003eContext\u003c/strong\u003e\u003c/em\u003e:\u003c/p\u003e\n\u003cp\u003eLauraceae species have become key components of temperate coastal forests, particularly following the decline of pine trees. The wood-boring beetle \u003cem\u003eEupromus ruber\u003c/em\u003e, known to infest Lauraceae, is expanding its distribution in these forests, potentially impacting tree health and forest ecosystems.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u003cstrong\u003eAims\u003c/strong\u003e\u003c/em\u003e:\u003c/p\u003e\n\u003cp\u003eThis study aims to investigate the invasion of \u003cem\u003eE. ruber\u003c/em\u003e, identify preferred Lauraceae host trees, and evaluate whether oviposition and larval boring increase the risk of stem breakage in temperate coastal forests.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u003cstrong\u003eMethods:\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eField surveys were conducted in coastal forests to assess the extent of damage caused by \u003cem\u003eE. ruber \u003c/em\u003eon its host tree, \u003cem\u003eMachilus thunbergii\u003c/em\u003e. The number of oviposition scars and stem breakage were recorded for individual trees. Generalized linear models (GLMs) were used to evaluate environmental factors affecting \u003cem\u003eE. ruber\u003c/em\u003e activity and the association of \u003cem\u003eE. ruber\u003c/em\u003e with stem breakage in its host.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u003cstrong\u003eResults\u003c/strong\u003e\u003c/em\u003e:\u003c/p\u003e\n\u003cp\u003eGLM analysis revealed a positive correlation between the number of oviposition scars and both tree height and relative photosynthetic photon flux density (rPPFD), indicating that \u003cem\u003eE. ruber\u003c/em\u003e preferentially oviposits on taller, sun-exposed \u003cem\u003eM. thunbergii\u003c/em\u003e trees. Stem breakage was associated with the presence of oviposition and larval boring, suggesting that \u003cem\u003eE. ruber\u003c/em\u003eactivity increases the risk of stem failure in its host.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u003cstrong\u003eConclusion\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eE. ruber\u003c/em\u003e infestation weakens\u003cem\u003e M. thunbergii\u003c/em\u003e stems, increasing breakage risk in snowy coastal forests. Monitoring and integrated management are crucial for maintaining forest stability.\u003c/p\u003e","manuscriptTitle":"Impacts of the pest wood-boring beetle, Eupromus ruber, on Lauraceae species in temperate coastal forests","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-24 06:47:40","doi":"10.21203/rs.3.rs-8025870/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"411a38dc-c5c2-4008-a109-c79c0c23434b","owner":[],"postedDate":"November 24th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-02-16T08:11:51+00:00","versionOfRecord":[],"versionCreatedAt":"2025-11-24 06:47:40","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8025870","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8025870","identity":"rs-8025870","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}