Forecasting life table parameters of Cabbage Aphid Brevicone brassica (L.)Hemiptera: Aphididae using differential Nitrogen-regimes in kale

Forecasting life table parameters of Cabbage Aphid Brevicone brassica (L.)Hemiptera: Aphididae using differential Nitrogen-regimes in kale | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Forecasting life table parameters of Cabbage Aphid Brevicone brassica (L.)Hemiptera: Aphididae using differential Nitrogen-regimes in kale Anisa Ayub, Altaf Hussain This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7863911/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 The interactions between plants and herbivores are influenced by the increased application of nitrogen to crops, which has the potential to enhance the growth of herbivore populations. This study evaluates the impact of nitrogen fertilization on the life table parameters of cabbage aphid using kale ( Brassica oleracea var. acephala ) as a host plant under controlled greenhouse conditions. Nine nitrogen treatments (ranging from 0% to 200% of the recommended dose) were applied, while other biotic and abiotic factors were kept constant. Aphid performance was assessed based on developmental and reproductive metrics, including pre-reproductive period, reproductive and post-reproductive periods, adult longevity, mean daily fecundity, net reproductive rate (R₀), intrinsic rate of increase (rₘ), finite rate of increase (λ), mean generation time (T), and population doubling time. Linear regression models revealed strong, statistically significant relationships between nitrogen levels and cabbage aphid’s life history traits. Increased nitrogen availability extended reproductive and post-reproductive periods, enhanced mean daily fecundity, and reduced the pre reproductive period, mean generation and doubling times, leading to faster population growth. While as the intrinsic rate of increase and net reproductive rate both showed robust positive correlations with nitrogen levels (R² >0.9, p < 0.001). These results highlight the critical influence of nitrogen in shaping pest population dynamics and stress the importance of balanced fertilization strategies. Excessive nitrogen application, while promoting plant growth, can inadvertently intensify aphid infestations. The study advocates for integrated pest and nutrient management approaches to sustainably mitigate the pest pressures on kale plant . Cabbage aphid Nitrogen fertilization Kale (Brassica oleracea var. acephala) Intrinsic rate of increase (rₘ) Net reproductive rate (R₀) Finite rate of increase (λ) Mean generation time (T) Population doubling time Integrated pest management (IPM) Figures Figure 1 Figure 2 Introduction The cabbage aphid, Brevicoryne brassicae (L.) (Hemiptera: Aphididae), originally native to Europe, is now distributed worldwide (Rivnay, 1962 ). It is a major pest of Brassicaceae crops, causing direct damage through feeding and serving as a vector for numerous plant viruses, transmitting nearly 20 viral diseases to a wide range of hosts (Eastop and Blackman, 2000 ; Ellis et al., 1998 ). Chemical pesticides have long been the primary strategy for aphid management; however, indiscriminate use has led to serious environmental consequences (Furk and Hines, 1993 ; Saldo and Szpyrka, 2009 ).The performance of herbivorous insects, including cabbage aphids, is influenced by host plant quality—particularly carbon and nitrogen content—as well as defensive chemicals and physical traits (Awmack and Leather, 2002). Fertilizers are widely applied to improve crop quality and maximize yield (Chau et al., 2005 ). Nevertheless, several studies have demonstrated that nitrogen fertilization enhances aphid growth, fecundity, and development rate, ultimately increasing population density (Pettit et al., 1994; Nevo and Coll, 2001 ; Jansson and Ekbom, 2002 ). As phytophagous insects are often limited by nitrogen availability, this macronutrient plays a crucial role in shaping population dynamics (Denno et al., 2002 ; Behmer, 2009 ). In particular, nitrogen enrichment significantly boosts aphid fecundity and reproductive success (Bentz et al., 1995 ; Nevo and Coll, 2001 ).Nitrogen-enriched phloem sap benefits aphids and other phloem-feeding insects, whereas chewing insects such as moths and grasshoppers often suffer from elevated defensive compound concentrations present in leaf tissues (Awmack and Leather, 2002; Behmer, 2009 ). Conversely, nitrogen deficiency has been shown to reduce aphid intrinsic rates of increase, as reported in multiple species (Douglas, 1993 ), including Rhopalosiphum padi (Ponder et al., 2000 ). Thus, soil nitrogen management can significantly affect crop susceptibility to pests without necessarily reducing plant yield (Phelan et al., 1995 ).Excess nitrogen inputs also modify plant morphology (Simpson and Simpson, 1990), which may enhance herbivore growth, survival, and reproduction (Barbour et al., 1991 ; Leather, 1994). Factors such as plant species, variety, and soil nutrient status strongly influence aphid reproduction, growth, and longevity (Evans, 1938 ). Aphid fecundity is positively correlated with nitrogen content, though responses vary across species, suggesting that nitrogen concentration may serve as an indicator of host plant suitability (Van Emden and Bashford, 1969 ). Understanding pest population dynamics is therefore central to effective pest control (Cammell and Knight, 1992 ; Reuveni, 1995; van Emden and Harrington, 2007; Abrol, 2014). Since shorter development time extends reproductive opportunities and longer reproductive periods increase lifetime fecundity, aphids experiencing favorable nitrogen conditions can produce more offspring, intensifying outbreaks (Mousa et al., 2019 ).Given these dynamics, this study employs Brevicoryne brassicae on Brassica oleracea var. acephala (kale) to investigate how varying levels of nitrogen fertilizer influence the life table parameters of cabbage aphids. Materials and method Study location and rearing conditions The experiments were conducted in controlled environmental chambers at the Entomology Laboratory Department of Zoology, University of Kashmir, to determine the effect of N applications to kale ( Brassica oleracea var. acephala ) on the developmental periods and life table parameters of Brevicoryne brassica . The mean temperature controlled conditions at 25 ± 2°C, 60–70% RH and maintained on a photoperiod regime of 12L:12D-hr photoperiods Insect source Cabbage aphid were initially collected from naturally infested kale plants ( Brassica oleracea var. acephala ) grown in the fields and subsequently reared under greenhouse conditions. Seeds were sown in plastic pots (15 cm height, 12 cm base diameter, 17.8 cm surface diameter) with a surface area of 248.48 cm², filled with cocopeat, a nutrient-free medium. No fertilizers were added at the time of sowing. Plants were watered individually to maintain optimal moisture. Aphid colonies were reared on kale plants supplied with the recommended dose of nitrogen for about two generations to acclimatize them to experimental conditions. The recommended doses per 248.58 cm² area, calculated from hectare-based guidelines (90 kg N/ha, 60 kg P/ha, and 60 kg K/ha as per SKAUST-Kashmir), were 0.2237 g nitrogen (from 0.3241 g DAP and 0.3595 g urea), 0.1491 g phosphorus (from 0.3241 g DAP), and 0.1491 g potassium (from 0.3594 g potassium sulfate). Aphids used in the experiment were obtained from these laboratory-reared colonies. Experimental design. Cabbage aphids ( Brevicoryne brassicae ) were reared on kale plants ( Brassica oleracea var. acephala ) grown under nine nitrogen treatments to assess the effects of nitrogen levels on their life table parameters. The nitrogen treatments included: 0%, 25%, 50%, 75%, 100%, 125%, 150%, 175%, and 200% of the recommended nitrogen dose—were applied, each replicated 20 times, while other biotic and abiotic factors were kept constant across treatments, and all treatments were applied in three equal splits during early vegetative, mid-vegetative, and pre-reproductive stages of the plant. Cocopeat, a nutrient-free medium, was used to ensure nitrogen was the only varying nutrient. To establish a cohort of first-instar nymphs of uniform age (< 24 h old), one apterous adult female aphid from a colony which were reared on recommended nitrogen dose plants was placed on each kale plant. After four hours, all aphids were removed except for one newly born nymph per plant. A compact plastic enclosure (clip-cage with an inner diameter of 3.2 cm). was attached to a single leaf on each kale plant in every pot for conducting the experiments. The enclosures were sufficiently sized to ensure that neither nourishment nor area constrained the study (Eini et al 2017 ). Each treatment was replicated 20 times (one plant per replication). Aphids were observed daily from birth until death. Statistical analysis and modelling Linear regression analysis was performed to determine the relationship between nitrogen levels and life table parameters of cabbage aphid viz Total longevity, pre-reproductive period, reproductive period, and post-reproductive period, mean daily fecundity (MDF), net reproductive rate (R 0 ), intrinsic rate of increase (r m ), Finite rate of increase (λ), mean generation time (T),Doubling time (t) For each trait, a linear model was fitted using nitrogen as the predictor variable. The assumptions of normality, homoscedasticity, and model validity were assessed using graphical residual diagnostics (Fig. 2). All data analyses were conducted using R statistical environment (R Core Team, 2024). The initial diagnostics for the relationship between nitrogen and mean daily fecundity indicated a violation of the linearity assumption and visual inspection of the data suggested a non-linear pattern. Consequently, to model the non-linear relationship between nitrogen and mean daily fecundity, a generalized additive model (GAM) was employed using the ‘ mgcv ’ package (Wood, 2017). Life table parameters Table 1 Demographic variables assessed in age-stage life table analyses of the cabbage aphid ( Brevicoryne brassicae ) reared on kale ( Brassica oleracea var. acephala ). Parameters Explanation age-specific fecundity (mₓ) m x = nymphs produced at age x /aphids alive at age x Represents survival probability to age x and mean fecundity at age x. Age-specific survival rate(l x ) l x =n x /n 0 l x ​ represents the proportion of individuals surviving at the beginning of each specific age or stage ( x ) out of the original cohort n x = Number of cabbage aphid alive at age x n 0 = initial number of cabbage aphid at age 0(the starting population) Net reproductive rate (R₀) \(\:{R}_{0}=\:\sum\:(\text{l}x\cdot\:\text{m}x)\) Indicates total expected number of offspring an individual can produce during its lifetime. Intrinsic rate of increase (r m ) r m ≈ ln R 0 /T Population growth rate under ideal conditions (Birch 1948 ). Finite rate of increase (λ) λ = eʳ Represents population growth multiplier per time unit. Mean generation time (T) T = ln(R₀)/r Average time from birth of parents to birth of offspring. Doubling time (t d ) t d = ln 2 /r m, refers to the period required for a population of cabbage aphids ( Brevicoryne brassicae ) to double in number under specific environmental conditions Mean daily fecundity (MDF) MDF = Total Fecundity​/Lifespan Number of nymphs produced by female aphid per day Developmental period (Dp) Time taken (in days) from birth to attainment of adult stage by cabbage aphids under specified greenhouse conditions. Pre-reproductive period (Pr) Duration (in days) from the adult emergence to the first reproduction event (first offspring production). Reproductive period (Rp) The span (in days) during which a cabbage aphid adult actively reproduces and produces offspring. Post-reproductive period (Pp) The time (in days) from the last reproductive event to the death of the individual. Total Longevity (TL) Total lifespan (in days) of cabbage aphid from birth to death, including developmental, reproductive, and post-reproductive periods. Results Nitrogen fertilization had a substantial effect on multiple biological and life table parameters of cabbage aphids ( Brevicoryne brassicae ) reared on kale ( Brassica oleracea var. acephala ). Regression analyses revealed that nitrogen concentration positively influenced longevity, reproductive period, post-reproductive period, intrinsic rate of increase (r), finite rate of increase (λ), net reproductive rate (R₀), and fecundity, while negatively affecting pre-reproductive period, generation time (T), and doubling time. The longevity of aphids increased significantly with nitrogen application (R² = 0.93, p < 0.001), following the regression equation y = 0.016 N + 18.2. The regression slope indicates that for every 1% increase in nitrogen, aphid lifespan increases by approximately 0.016 days Fig. (1d) Similarly, the reproductive period showed a strong positive linear relationship ( y = 0.012 N + 8.04, R² = 0.98, p < 0.01), suggesting that for every 1% increase in nitrogen, the reproductive period increases by 0.012 days and the post-reproductive period increased according to y = 0.01 N + 1.34 (R² = 0.98, p < 0.01), the slope of 0.01 suggests that for every 1% increase in nitrogen Fig. (1a). The post-reproductive period extends by 0.01 days Fig. (1c) In contrast, the pre-reproductive period decreased with higher nitrogen levels ( y = − 0.007 N + 8.8, R² = 0.78, p < 0.01), indicates that at 0% nitrogen, the predicted pre-reproductive period is 8.8 days, and for every 1% increase in nitrogen, the pre-reproductive period decreases by 0.007 days (Fig. 1b), suggesting a negative correlation between nitrogen levels and the time before aphid begin reproducing. The net reproductive rate (R₀) increased linearly ( y = 0.09 N + 29.2, R² = 0.90, p < 0.001),the regression equation suggests that for every 1% increase in nitrogen, R₀ increases by 0.09 units (Fig. 1e), indicating enhanced fecundity with nitrogen enrichment. Intrinsic rate of increase (r) also rose with nitrogen application ( y = 0.007 N + 0.20, R² = 0.94, p < 0.001), reaching approximately 0.35 at 200% nitrogen and for every 1% increase in nitrogen, the intrinsic rate of increase (r) of the aphid population increases by 0.007 (Fig. 1f). Similarly, the finite rate of increase (λ) increased linearly ( y = 0.009 N + 1.25, R² = 0.94, p < 0.001), for every 1% increase in nitrogen, λ increases by 0.009. At 0% nitrogen, finite rate of increase λ starts at 1.25 units (Fig. 1g) highlighting faster population growth. Mean daily fecundity followed a non-linear pattern with a plateau at higher nitrogen concentrations (R² = 0.86, p < 0.002), suggesting diminishing returns in reproduction beyond a threshold. The GAM revealed a significant non-linear effect of nitrogen on mean daily fecundity (Fig. 1h) The smooth term for nitrogen was highly significant ( p < 0.001 ). The model explained a substantial amount of the variation in mean daily fecundity (R² = 0.86), deviance explained = 90.4%). The fitted relationship showed that MDF increased sharply as nitrogen levels rose from 0% to approximately 100%, after which the positive effect diminished, and mean daily fecundity levels plateaued at higher nitrogen concentrations. Mean generation time (T) decreased linearly with nitrogen application ( y = − 0.02 N + 14.8, R² = 0.90, p < 0.001), This indicates that for every 1% increase in nitrogen, the generation time decreases by 0.02 days(Fig. 1i). while doubling time reduced as well ( y = − 0.006 N + 3.03, R² = 0.93, p < 0.001), Indicates that with each 1% increase in nitrogen, doubling time decreases by 0.006 days (Fig. 1j), reflecting accelerated population turnover. Overall, model diagnostics confirmed the robustness of all regressions, with residuals displaying approximate normality, minimal heteroscedasticity, and no major influential outliers. These findings strongly suggest that nitrogen enrichment enhances aphid survival and reproductive potential, which may lead to higher infestation risks under excessive nitrogen fertilization. Table 2 Developmental period parameters Regression Analysis Parameter Regression Equation R² p-value Interpretation Reproductive Period y = 0.012x + 8.04 0.98 <0.01 Prolongs with increased N Pre-Reproductive Period y = -0.007x + 8.8 0.78 <0.01 Decreases with increased N Post-Reproductive Period y = 0.01x + 1.34 0.98 <0.01 Increases with increased N Longevity y = 0.016x + 18.2 0.93 <0.001 Positively influenced by N Table 3 Life Table Parameters Regression Analysis Parameter Regression Equation R² p-value Interpretation Net Reproductive Rate (R 0 ) y = 0.09x + 29.2 0.90 < 0.001 Higher nitrogen enhances fecundity Intrinsic Rate of Increase (r) y = 0.007x + 0.20 0.94 < 0.001 Accelerated population growth Finite Rate of Increase (λ) y = 0.009x + 1.25 0.94 < 0.001 Positively correlated with N Mean Generation Time (T) y = -0.02x + 14.8 0.90 < 0.001 Shortened with increased N Doubling Time (Dt) y = -0.006x + 3.03 0.93 < 0.001 Declines with higher N levels Discussion Nitrogen levels within the host plant significantly influence various aspects of aphid biology, including development rate, physical characteristics, life history traits, and the proportional production of winged versus wingless morphs (Dixon, 1987 ). Host plant nitrogen concentration significantly influences aphid reproductive patterns and seasonal population dynamics, altering both the timing and intensity of their reproductive cycles throughout the year (Dixon et al., 1993 ). Our study confirmed that nitrogen availability exhibited significant positive impacts on multiple demographic parameters of aphid populations. Elevated nitrogen concentrations resulted in prolonged reproductive and post-reproductive phases and shrinks the pre reproductive period of the cabbage aphid, however Increases in nitrogen rates on wheat (in hydroponic culture) did not substantially alter the length of the pre-reproductive phase, the reproductive period, longevity, or the reproductive rate of the Russian wheat aphid, Diuraphis noxia (Kurdjumov), according to Moon et al. ( 1995 ) but the studies of Zarghami et al ( 2010 ) revealed that the nitrogen fertilisation levels positively correlates with cabbage aphid ( Brevicoryne brassicae ) performance on oilseed rape ( RGS003 cultivar) and reported that a higher level of nitrogen fertilisation resulted in a shorter pre-reproductive phase overall, but it had no discernible effect on lifespan. In agreement to our results Fallahpour et al. ( 2015 ) observed that aphid developmental periods shortened as nitrogen concentrations increased, demonstrating a significant inverse relationship between host plant nitrogen content and aphid development time. The net reproductive rate (R₀) showed increased linearly trend with the increase of nitrogen fertiliser (, R² = 0.90, p < 0.001), indicating enhanced fecundity with nitrogen enrichment. In our experiment the mean daily fecundity exhibited a distinctive non-linear response pattern with respect to nitrogen concentration, characterized by a saturation plateau at higher nitrogen levels (R² = 0.86, p < 0.002). This asymptotic relationship indicates potential physiological constraints on reproductive output, suggesting diminishing reproductive returns beyond a critical nitrogen threshold. This phenomenon may reflect inherent limitations in the aphid's capacity to convert additional nutritional resources into offspring production once baseline nutritional requirements have been sufficiently met. These findings align with initial observations of enhanced A. gossypii fecundity with nitrogen application on cucumber (Pettit et al. 1994) and cotton (Rosenheim et al. 1994 ; Nevo and Coll 2001 ). Conversely, nitrogen fertilization showed no impact on reproductive output for A. gossypii on chrysanthemums (Bethke et al. 1998 ) or D. noxia on wheat (Moon et al. 1995 ). Fallahpour et al. ( 2015 ) also demonstrated increased Lipaphis erysimis fecundity with higher nitrogen levels across three canola cultivars (Zarfam, Okapi, Modena). Excessive nitrogen application (120–130 kg/acre) in wheat increases aphid infestations despite higher ladybird beetle activity, while moderate nitrogen (90 kg/acre) minimizes pest pressure (Maqsood et al 2025).Comparable fecundity enhancements with elevated nitrogen were documented for Aphis gossypii on cucumber (Hosseini et al., 2010 ) and cotton (Nevo and Coll, 2001 ), and for Brevicoryne brassicae on oilseed rape (Brassica napus) (Zarghami et al., 2010 ). Alasvand Zarasvand et al. (2015) observed that the varied amounts of Nitrogen had little effect on pre- and post-reproductive periods but had substantial influence on reproductive period, adult longevity and fecundity of Schizaphis graminum ( Rondani). The studies of Eini et al ( 2017 ) indicated that the fecundity of A. gossypii decreased with the increasing amount of nitrogen. Furthermore, Aqueel and Leather ( 2011 ) found nitrogen fertilizer positively affected Sitobion avenae (F) and Rhopalosiphum padi (L) fecundity on wheat plants. Hosseini et al. (2015) observed maximum A. craccivora Koch reproduction at 100% recommended nitrogen levels with minimum reproduction in unfertilized plants. Hosseini et al. (2014) reported comparable findings for Lipaphis erysimi (Kalt). Khattak et al. ( 1998 ) demonstrated that nitrogen fertilizer applied independently increased Brevicoryne brassicae (L) populations on canola, whereas combined nitrogen and phosphorus applications reduced pest numbers. Concurrently, our results showed that both mean generation time (T) and population doubling time (Dt) were found to be inversely proportional to nitrogen availability, facilitating accelerated population growth dynamics. Eini et al ( 2017 ) revealed that Nitrogen fertilizer levels significantly influenced mean generation time ( T) and population doubling time (Dt ) of Aphis gossypii on cucumber plant. But according to primary results of Hosseini et al ( 2010 ) there is no significant effect of increasing nitrogen fertiliser on mean generation time but significant effect on doubling time of the cotton aphid on cucumber plants. Population intrinsic growth rate (r m ) variations stem primarily from three biological parameters: developmental rate, fecundity, and longevity (Dixon, 1987 ). This metric serves as an essential indicator for quantifying environmental factor effects on population dynamics. Throughout the experiment, the intrinsic rate of increase (r m ) showed strong positive correlations (R² >0.9, p < 0.001) underscore the substantial explanatory power of nitrogen as a predictor variable for aphid population parameters. These results corroborate with previous findings of Hosseini et al. ( 2010 ) and showed that Nitrogen fertilization significantly influenced the intrinsic rate of natural increase (r m ) of A. gossypii , with r m values rising proportionally to nitrogen application rates. Zargami et al ( 2010) also showed that increase in nitrogen fertilization levels on oilseed rape plants resulted in increase in r m of Brevicoryne brassica e. Nevo and Coll ( 2001 ) similarly demonstrated that elevated nitrogen fertilization in cotton systems corresponds with increased intrinsic growth rate (r m ) in A. gossypii populations. Similarly the studies conducted by Fallahpour et al ( 2015 ) found that there is a significant positive effect of nitrogen fertiliser on the r m of aphid and Gao et al ( 2025 ) also found that Nitrogen fertilization improved plant growth (height, biomass) and biochemical traits (nitrogen, chlorophyll, tannin), while also enhancing aphid life history parameters (longevity, fecundity, population growth rates) Conversely, Jansson and Smilowitz ( 1986 ) reported diminished Myzus persicae population growth rates at maximum nitrogen levels on potatoes. Chau et al. ( 2005 ) documented increasing A. gossypii population growth on chrysanthemum as nitrogen rates rose from 0 to 38 ppm, followed by stabilization between 38 and 488 ppm. Cole ( 1997 ) determined that concentrations of key amino acids—tyrosine, alanine, leucine, and glutamic acid—explained 43% of variation in aphid intrinsic growth rates, with elevated tyrosine and glutamic acid levels specifically enhancing aphid performance parameters. These findings align with established phloem-feeding insect nutritional ecology models, wherein host plant nitrogen content directly influences phloem sap compositional quality, particularly amino acid profiles and concentrations. The observed demographic responses likely reflect the physiological mechanisms through which enhanced nutritional substrate availability translates to improved reproductive efficiency and developmental outcomes in aphid populations. The magnitude of these effects suggests that nitrogen may function as a primary limiting factor in aphid population growth within agricultural and natural ecosystems. Conclusion This study underscores the profound ecological impact of nitrogen fertilization on the population dynamics of Brevicoryne brassicae . Nitrogen-enriched kale plants enhanced aphid longevity, reproduction, and developmental rates, resulting in a faster generational turnover. These improvements can be attributed to the enhanced nutritional quality of host plants, particularly the increased availability of nitrogen-rich phloem sap, which likely made them more palatable and nutritious for the aphids. Extended lifespan allowed aphids to reproduce over a longer period, thereby increasing total offspring and supporting larger populations. A prolonged reproductive phase further amplified reproductive success, while a longer post-reproductive lifespan indicated better overall vitality and health of aphids on nitrogen-rich plants. Furthermore, a shorter pre-reproductive period demonstrated faster development to reproductive maturity, which accelerated population establishment and growth. The observed increase in fecundity and net reproductive rate (R₀) indicates enhanced energy availability for reproduction due to better host plant nutrition. Moreover, the rise in intrinsic rate of increase (r) and finite rate of increase (λ) with nitrogen reflects both higher reproductive output and a faster life cycle, resulting in rapid population multiplication under nitrogen-rich conditions.However, a notable plateau in daily mean fecundity at higher nitrogen concentrations Fig. (1h). suggests a physiological or nutritional threshold beyond which further increases in nitrogen do not translate into proportional reproductive gains. This threshold effect may reflect limitations in nutrient assimilation or the biological capacity of aphids. Similarly, a reduction in generation time (T) and doubling time (D t ) under increased nitrogen conditions points to quicker generational turnover and faster population doubling—critical factors in pest outbreaks. Collectively, the evidence indicates that nitrogen is a key driver of aphid population dynamics, enhancing nearly all life table parameters. While nitrogen supports crop growth, excessive fertilization poses a risk of pest escalation, particularly for sap-feeding insects like B. brassicae . Therefore, strategic nitrogen management is crucial not only for optimizing plant health and productivity but also for mitigating pest outbreaks as part of integrated pest management (IPM) strategies. Declarations Conflict of interest: The author confirms that there are no known financial or personal conflicts that could have influenced the work reported in this manuscript. Funding: The author gratefully acknowledges financial support from the Council of Scientific and Industrial Research – Human Resource Development Group (CSIR-HRDG), New Delhi, India [File No. / Grant No. 09/0251(17624)/2024-EMR-I]. Author Contribution Authors contribution Title of Manuscript: Forecasting life table parameters of Cabbage Aphid Brevicoryne brassica (L.)Hemiptera: Aphididae using differential Nitrogen-regimes in kale Corresponding Author1•Full Name: Dr. Anisa Ayub•Affiliation: Department of Zoology, university of Kashmir [Srinagar , jammu and Kashmir , India •Email: [ [email protected] ]•ORCID ID:0009-0006-4443-3539•Phone Number: [7006821513l]Corresponding author2 •Full Name: Altaf Hussain Mir •Affiliation: university of Kashmir ]•Email: [email protected] •Contribution: Statistical analysis, supervision, and critical revision of the manuscript.Author Contributions•Anisa Ayub: Conceptualisation, experiment design, data collection, interpretation of results, manuscript writing.•Dr. Altaf Hussain Mir: Statistical analysis, model validation, supervision, and manuscript review.AcknowledgementWe thank the Council of Scientific and Industrial Research (CSIR), India, for funding support. We also extend our gratitude to laboratory and greenhouse staff who assisted in maintaining plant and aphid cultures.Funding StatementThe author gratefully acknowledges financial support from the Council of Scientific and Industrial Research – Human Resource Development Group (CSIR-HRDG), New Delhi, India [File No. / Grant No. 09/0251(17624)/2024-EMR-I]. Acknowledgement AcknowledgementWe thank the Council of Scientific and Industrial Research (CSIR), India, for funding support. We also extend our gratitude to laboratory and greenhouse staff who assisted in maintaining plant and aphid cultures. We express our sincere thanks to the Head of the Department of Zoology for providing the necessary facilities and encouragement throughout the study. References Alasvand Zarasvand, A., Allahyari, H., & Fattah-Hosseini, S. (2013). Effect of nitrogen fertilisation on biology, life table parameters and population abundance of greenbug; Schizaphis graminum (Rondani)(Hemiptera: Aphididae). 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Entomologia experimentalis et applicata , 12 (3), 351-364. Zarghami, S., Allahyari, H., Bagheri, M. R., & Saboori, A. (2010). Effect of nitrogen fertilization on life table parameters and population growth of Brevicoryne brassicae. Bulletin of Insectology , 63 (1), 39-43. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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10:07:17","extension":"xml","order_by":67,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":105759,"visible":true,"origin":"","legend":"","description":"","filename":"c43fa9b534424ec9bc0ae916dd04ffd11structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-7863911/v1/3c1408ecdb3a3cf6ad5e208c.xml"},{"id":95526702,"identity":"467115eb-095a-4300-81c6-dc66bd3ff35a","added_by":"auto","created_at":"2025-11-10 10:07:38","extension":"html","order_by":68,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":120680,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7863911/v1/2497be042a852674ecca9507.html"},{"id":95385362,"identity":"f90640e5-73b0-4fab-bbc0-8220fe0e346b","added_by":"auto","created_at":"2025-11-07 12:51:34","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":111522,"visible":true,"origin":"","legend":"\u003cp\u003eThis figure illustrates the effect of nitrogen treatments (measured in grams per cm²) on various biological and life table parameters of cabbage aphid (\u003cem\u003eBrevicoryne brassicae\u003c/em\u003e) reared on kale (\u003cem\u003eBrassica oleracea\u003c/em\u003e var. \u003cem\u003eacephala\u003c/em\u003e). The subfigures include: (a) reproductive period (days), (b) pre-reproductive period (days), (c) post-reproductive period (days), (d) adult longevity (days), (e) net reproductive rate (R₀), (f) intrinsic rate of increase (r), (g) finite rate of increase (λ), (h) mean daily fecundity, (i) mean generation time (T, days), and (j) doubling time (Dt, days). In each subfigure, the x-axis represents nitrogen treatment levels (g/cm²), while the y-axis denotes the corresponding parameter value.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7863911/v1/674c8d673857f85384dfa6fb.png"},{"id":95385363,"identity":"8499c570-c884-4410-b9c6-3e7c36d0d3ba","added_by":"auto","created_at":"2025-11-07 12:51:34","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":323207,"visible":true,"origin":"","legend":"\u003cp\u003eThis figure presents diagnostic plots for model fitting of various biological and life table parameters of cabbage aphid (Brevicoryne brassicae) reared on kale (Brassica oleracea var. acephala) under different nitrogen treatments (g per cm²). The parameters analyzed include: (a) Reproductive period, (b)Pre-reproductive period, (c) post-reproductive period, (d)adult longevity,(e) net reproductive rate (R₀), (f)intrinsic rate of increase (r), (g)finite rate of increase (λ), (h) mean daily fecundity,(i) mean generation time (T), and (j)doubling time (Dt). The following models were used to fit the data: linear, regression for all and non-linear regression for the MDF. The representative diagnostic plots including: (1) Residuals vs Fitted, (2) Normal Q-Q plot, (3) Scale-Location plot, and (4) Residuals vs Leverage with Cook’s distance. These plots evaluate model assumptions such as linearity, homoscedasticity, normality of residuals, and influence of data points.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7863911/v1/8aead33a67ff076a660d418e.png"},{"id":96992021,"identity":"ab38d2c1-5988-4922-9b38-6ab0be640edf","added_by":"auto","created_at":"2025-11-28 11:24:18","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1067736,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7863911/v1/8256e877-913c-44c1-8076-49158b47f4cd.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Forecasting life table parameters of Cabbage Aphid Brevicone brassica (L.)Hemiptera: Aphididae using differential Nitrogen-regimes in kale","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe cabbage aphid, \u003cem\u003eBrevicoryne brassicae\u003c/em\u003e (L.) (Hemiptera: Aphididae), originally native to Europe, is now distributed worldwide (Rivnay, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e1962\u003c/span\u003e). It is a major pest of Brassicaceae crops, causing direct damage through feeding and serving as a vector for numerous plant viruses, transmitting nearly 20 viral diseases to a wide range of hosts (Eastop and Blackman, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2000\u003c/span\u003e; Ellis et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e1998\u003c/span\u003e). Chemical pesticides have long been the primary strategy for aphid management; however, indiscriminate use has led to serious environmental consequences (Furk and Hines, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e1993\u003c/span\u003e; Saldo and Szpyrka, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2009\u003c/span\u003e).The performance of herbivorous insects, including cabbage aphids, is influenced by host plant quality\u0026mdash;particularly carbon and nitrogen content\u0026mdash;as well as defensive chemicals and physical traits (Awmack and Leather, 2002). Fertilizers are widely applied to improve crop quality and maximize yield (Chau et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2005\u003c/span\u003e). Nevertheless, several studies have demonstrated that nitrogen fertilization enhances aphid growth, fecundity, and development rate, ultimately increasing population density (Pettit et al., 1994; Nevo and Coll, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2001\u003c/span\u003e; Jansson and Ekbom, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2002\u003c/span\u003e). As phytophagous insects are often limited by nitrogen availability, this macronutrient plays a crucial role in shaping population dynamics (Denno et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2002\u003c/span\u003e; Behmer, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). In particular, nitrogen enrichment significantly boosts aphid fecundity and reproductive success (Bentz et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e1995\u003c/span\u003e; Nevo and Coll, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2001\u003c/span\u003e).Nitrogen-enriched phloem sap benefits aphids and other phloem-feeding insects, whereas chewing insects such as moths and grasshoppers often suffer from elevated defensive compound concentrations present in leaf tissues (Awmack and Leather, 2002; Behmer, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). Conversely, nitrogen deficiency has been shown to reduce aphid intrinsic rates of increase, as reported in multiple species (Douglas, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e1993\u003c/span\u003e), including \u003cem\u003eRhopalosiphum padi\u003c/em\u003e (Ponder et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2000\u003c/span\u003e). Thus, soil nitrogen management can significantly affect crop susceptibility to pests without necessarily reducing plant yield (Phelan et al., \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e1995\u003c/span\u003e).Excess nitrogen inputs also modify plant morphology (Simpson and Simpson, 1990), which may enhance herbivore growth, survival, and reproduction (Barbour et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e1991\u003c/span\u003e; Leather, 1994). Factors such as plant species, variety, and soil nutrient status strongly influence aphid reproduction, growth, and longevity (Evans, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e1938\u003c/span\u003e). Aphid fecundity is positively correlated with nitrogen content, though responses vary across species, suggesting that nitrogen concentration may serve as an indicator of host plant suitability (Van Emden and Bashford, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e1969\u003c/span\u003e). Understanding pest population dynamics is therefore central to effective pest control (Cammell and Knight, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e1992\u003c/span\u003e; Reuveni, 1995; van Emden and Harrington, 2007; Abrol, 2014). Since shorter development time extends reproductive opportunities and longer reproductive periods increase lifetime fecundity, aphids experiencing favorable nitrogen conditions can produce more offspring, intensifying outbreaks (Mousa et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).Given these dynamics, this study employs \u003cem\u003eBrevicoryne brassicae\u003c/em\u003e on \u003cem\u003eBrassica oleracea\u003c/em\u003e var. \u003cem\u003eacephala\u003c/em\u003e (kale) to investigate how varying levels of nitrogen fertilizer influence the life table parameters of cabbage aphids.\u003c/p\u003e"},{"header":"Materials and method","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eStudy location and rearing conditions\u003c/h2\u003e\u003cp\u003eThe experiments were conducted in controlled environmental chambers at the Entomology Laboratory Department of Zoology, University of Kashmir, to determine the effect of N applications to kale (\u003cem\u003eBrassica oleracea\u003c/em\u003e var. \u003cem\u003eacephala\u003c/em\u003e) on the developmental periods and life table parameters of \u003cem\u003eBrevicoryne brassica\u003c/em\u003e. The mean temperature controlled conditions at 25\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u0026deg;C, 60\u0026ndash;70% RH and maintained on a photoperiod regime of 12L:12D-hr photoperiods\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eInsect source\u003c/h3\u003e\n\u003cp\u003eCabbage aphid were initially collected from naturally infested kale plants (\u003cem\u003eBrassica oleracea\u003c/em\u003e var. \u003cem\u003eacephala\u003c/em\u003e) grown in the fields and subsequently reared under greenhouse conditions. Seeds were sown in plastic pots (15 cm height, 12 cm base diameter, 17.8 cm surface diameter) with a surface area of 248.48 cm\u0026sup2;, filled with cocopeat, a nutrient-free medium. No fertilizers were added at the time of sowing. Plants were watered individually to maintain optimal moisture. Aphid colonies were reared on kale plants supplied with the recommended dose of nitrogen for about two generations to acclimatize them to experimental conditions. The recommended doses per 248.58 cm\u0026sup2; area, calculated from hectare-based guidelines (90 kg N/ha, 60 kg P/ha, and 60 kg K/ha as per SKAUST-Kashmir), were 0.2237 g nitrogen (from 0.3241 g DAP and 0.3595 g urea), 0.1491 g phosphorus (from 0.3241 g DAP), and 0.1491 g potassium (from 0.3594 g potassium sulfate). Aphids used in the experiment were obtained from these laboratory-reared colonies.\u003c/p\u003e\u003cp\u003e\u003cb\u003eExperimental design.\u003c/b\u003e\u003c/p\u003e\u003cp\u003eCabbage aphids (\u003cem\u003eBrevicoryne brassicae\u003c/em\u003e) were reared on kale plants (\u003cem\u003eBrassica oleracea\u003c/em\u003e var. \u003cem\u003eacephala\u003c/em\u003e) grown under nine nitrogen treatments to assess the effects of nitrogen levels on their life table parameters. The nitrogen treatments included: 0%, 25%, 50%, 75%, 100%, 125%, 150%, 175%, and 200% of the recommended nitrogen dose\u0026mdash;were applied, each replicated 20 times, while other biotic and abiotic factors were kept constant across treatments, and all treatments were applied in three equal splits during early vegetative, mid-vegetative, and pre-reproductive stages of the plant. Cocopeat, a nutrient-free medium, was used to ensure nitrogen was the only varying nutrient. To establish a cohort of first-instar nymphs of uniform age (\u0026lt;\u0026thinsp;24 h old), one apterous adult female aphid from a colony which were reared on recommended nitrogen dose plants was placed on each kale plant. After four hours, all aphids were removed except for one newly born nymph per plant. A compact plastic enclosure (clip-cage with an inner diameter of 3.2 cm). was attached to a single leaf on each kale plant in every pot for conducting the experiments. The enclosures were sufficiently sized to ensure that neither nourishment nor area constrained the study (Eini et al \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Each treatment was replicated 20 times (one plant per replication). Aphids were observed daily from birth until death.\u003c/p\u003e\n\u003ch3\u003eStatistical analysis and modelling\u003c/h3\u003e\n\u003cp\u003eLinear regression analysis was performed to determine the relationship between nitrogen levels and life table parameters of cabbage aphid viz Total longevity, pre-reproductive period, reproductive period, and post-reproductive period, mean daily fecundity (MDF), net reproductive rate (R\u003csub\u003e0\u003c/sub\u003e), intrinsic rate of increase (r\u003csub\u003em\u003c/sub\u003e), Finite rate of increase (λ), mean generation time (T),Doubling time (t) For each trait, a linear model was fitted using nitrogen as the predictor variable. The assumptions of normality, homoscedasticity, and model validity were assessed using graphical residual diagnostics (Fig.\u0026nbsp;2). All data analyses were conducted using R statistical environment (R Core Team, 2024). The initial diagnostics for the relationship between nitrogen and mean daily fecundity indicated a violation of the linearity assumption and visual inspection of the data suggested a non-linear pattern. Consequently, to model the non-linear relationship between nitrogen and mean daily fecundity, a generalized additive model (GAM) was employed using the \u0026lsquo;\u003cem\u003emgcv\u003c/em\u003e\u0026rsquo; package (Wood, 2017).\u003c/p\u003e\n\u003ch3\u003eLife table parameters\u003c/h3\u003e\n\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eDemographic variables assessed in age-stage life table analyses of the cabbage aphid (\u003cem\u003eBrevicoryne brassicae\u003c/em\u003e) reared on kale (\u003cem\u003eBrassica oleracea\u003c/em\u003e var. \u003cem\u003eacephala\u003c/em\u003e).\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"2\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eParameters\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eExplanation\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eage-specific fecundity (mₓ)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003em\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e= nymphs produced at age \u003cem\u003ex\u003c/em\u003e/aphids alive at age \u003cem\u003ex\u003c/em\u003e\u003c/p\u003e\u003cp\u003eRepresents survival probability to age x and mean fecundity at age x.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAge-specific survival rate(l\u003cem\u003ex\u003c/em\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003el\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e=n\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e/n\u003csub\u003e0\u003c/sub\u003e\u003c/p\u003e\u003cp\u003el\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e​\u003c/em\u003e represents the proportion of individuals surviving at the beginning of each specific age or stage (\u003cem\u003ex\u003c/em\u003e) out of the original cohort\u003c/p\u003e\u003cp\u003en\u003csub\u003ex\u003c/sub\u003e= Number of cabbage aphid alive at age \u003cem\u003ex\u003c/em\u003e\u003c/p\u003e\u003cp\u003en\u003csub\u003e0\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;initial number of cabbage aphid at age 0(the starting population)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNet reproductive rate (R₀)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{R}_{0}=\\:\\sum\\:(\\text{l}x\\cdot\\:\\text{m}x)\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\u003cp\u003eIndicates total expected number of offspring an individual can produce during its lifetime.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eIntrinsic rate of increase (r\u003csub\u003em\u003c/sub\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003er\u003csub\u003em\u003c/sub\u003e \u0026asymp; ln R\u003csub\u003e0\u003c/sub\u003e/T\u003c/p\u003e\u003cp\u003ePopulation growth rate under ideal conditions (Birch 1948 ).\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFinite rate of increase (λ)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eλ\u0026thinsp;=\u0026thinsp;eʳ\u003c/p\u003e\u003cp\u003eRepresents population growth multiplier per time unit.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMean generation time (T)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eT\u0026thinsp;=\u0026thinsp;ln(R₀)/r\u003c/p\u003e\u003cp\u003eAverage time from birth of parents to birth of offspring.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDoubling time (t\u003csub\u003ed\u003c/sub\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003et\u003csub\u003ed =\u003c/sub\u003e ln\u003csup\u003e2\u003c/sup\u003e/r\u003csub\u003em,\u003c/sub\u003e\u003c/p\u003e\u003cp\u003erefers to the period required for a population of cabbage aphids (\u003cem\u003eBrevicoryne brassicae\u003c/em\u003e) to double in number under specific environmental conditions\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMean daily fecundity (MDF)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMDF\u0026thinsp;=\u0026thinsp;Total\u0026nbsp;Fecundity​/Lifespan\u003c/p\u003e\u003cp\u003eNumber of nymphs produced by female aphid per day\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDevelopmental period (Dp)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTime taken (in days) from birth to attainment of adult stage by cabbage aphids under specified greenhouse conditions.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePre-reproductive period (Pr)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eDuration (in days) from the adult emergence to the first reproduction event (first offspring production).\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eReproductive period (Rp)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eThe span (in days) during which a cabbage aphid adult actively reproduces and produces offspring.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePost-reproductive period (Pp)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eThe time (in days) from the last reproductive event to the death of the individual.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTotal Longevity (TL)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTotal lifespan (in days) of cabbage aphid from birth to death, including developmental, reproductive, and post-reproductive periods.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eNitrogen fertilization had a substantial effect on multiple biological and life table parameters of cabbage aphids (\u003cem\u003eBrevicoryne brassicae\u003c/em\u003e) reared on kale (\u003cem\u003eBrassica oleracea var. acephala\u003c/em\u003e). Regression analyses revealed that nitrogen concentration positively influenced longevity, reproductive period, post-reproductive period, intrinsic rate of increase (r), finite rate of increase (λ), net reproductive rate (R₀), and fecundity, while negatively affecting pre-reproductive period, generation time (T), and doubling time. The longevity of aphids increased significantly with nitrogen application (R\u0026sup2; = 0.93, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001), following the regression equation \u003cem\u003ey\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.016\u003cem\u003eN\u003c/em\u003e\u0026thinsp;+\u0026thinsp;18.2. The regression slope indicates that for every 1% increase in nitrogen, aphid lifespan increases by approximately 0.016 days Fig.\u0026nbsp;(1d) Similarly, the reproductive period showed a strong positive linear relationship (\u003cem\u003ey\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.012\u003cem\u003eN\u003c/em\u003e\u0026thinsp;+\u0026thinsp;8.04, R\u0026sup2; = 0.98, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01), suggesting that for every 1% increase in nitrogen, the reproductive period increases by 0.012 days and the post-reproductive period increased according to \u003cem\u003ey\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.01\u003cem\u003eN\u003c/em\u003e\u0026thinsp;+\u0026thinsp;1.34 (R\u0026sup2; = 0.98, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01), the slope of 0.01 suggests that for every 1% increase in nitrogen Fig.\u0026nbsp;(1a). The post-reproductive period extends by 0.01 days Fig.\u0026nbsp;(1c) In contrast, the pre-reproductive period decreased with higher nitrogen levels (\u003cem\u003ey\u003c/em\u003e\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.007\u003cem\u003eN\u003c/em\u003e\u0026thinsp;+\u0026thinsp;8.8, R\u0026sup2; = 0.78, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01), indicates that at 0% nitrogen, the predicted pre-reproductive period is 8.8 days, and for every 1% increase in nitrogen, the pre-reproductive period decreases by 0.007 days (Fig.\u0026nbsp;1b), suggesting a negative correlation between nitrogen levels and the time before aphid begin reproducing. The net reproductive rate (R₀) increased linearly (\u003cem\u003ey\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.09\u003cem\u003eN\u003c/em\u003e\u0026thinsp;+\u0026thinsp;29.2, R\u0026sup2; = 0.90, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001),the regression equation suggests that for every 1% increase in nitrogen, R₀ increases by 0.09 units (Fig.\u0026nbsp;1e), indicating enhanced fecundity with nitrogen enrichment. Intrinsic rate of increase (r) also rose with nitrogen application (\u003cem\u003ey\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.007\u003cem\u003eN\u003c/em\u003e\u0026thinsp;+\u0026thinsp;0.20, R\u0026sup2; = 0.94, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001), reaching approximately 0.35 at 200% nitrogen and for every 1% increase in nitrogen, the intrinsic rate of increase (r) of the aphid population increases by 0.007 (Fig.\u0026nbsp;1f). Similarly, the finite rate of increase (λ) increased linearly (\u003cem\u003ey\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.009\u003cem\u003eN\u003c/em\u003e\u0026thinsp;+\u0026thinsp;1.25, R\u0026sup2; = 0.94, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001), for every 1% increase in nitrogen, λ increases by 0.009. At 0% nitrogen, finite rate of increase λ starts at 1.25 units (Fig.\u0026nbsp;1g) highlighting faster population growth. Mean daily fecundity followed a non-linear pattern with a plateau at higher nitrogen concentrations (R\u0026sup2; = 0.86, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.002), suggesting diminishing returns in reproduction beyond a threshold. The GAM revealed a significant non-linear effect of nitrogen on mean daily fecundity (Fig.\u0026nbsp;1h) The smooth term for nitrogen was highly significant (\u003cem\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/em\u003e). The model explained a substantial amount of the variation in mean daily fecundity (R\u0026sup2; = 0.86), deviance explained\u0026thinsp;=\u0026thinsp;90.4%). The fitted relationship showed that MDF increased sharply as nitrogen levels rose from 0% to approximately 100%, after which the positive effect diminished, and mean daily fecundity levels plateaued at higher nitrogen concentrations. Mean generation time (T) decreased linearly with nitrogen application (\u003cem\u003ey\u003c/em\u003e\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.02\u003cem\u003eN\u003c/em\u003e\u0026thinsp;+\u0026thinsp;14.8, R\u0026sup2; = 0.90, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001), This indicates that for every 1% increase in nitrogen, the generation time decreases by 0.02 days(Fig.\u0026nbsp;1i). while doubling time reduced as well (\u003cem\u003ey\u003c/em\u003e\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.006\u003cem\u003eN\u003c/em\u003e\u0026thinsp;+\u0026thinsp;3.03, R\u0026sup2; = 0.93, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001), Indicates that with each 1% increase in nitrogen, doubling time decreases by 0.006 days (Fig.\u0026nbsp;1j), reflecting accelerated population turnover. Overall, model diagnostics confirmed the robustness of all regressions, with residuals displaying approximate normality, minimal heteroscedasticity, and no major influential outliers. These findings strongly suggest that nitrogen enrichment enhances aphid survival and reproductive potential, which may lead to higher infestation risks under excessive nitrogen fertilization.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eDevelopmental period parameters Regression Analysis\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eParameter\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eRegression Equation\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eR\u0026sup2;\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003ep-value\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eInterpretation\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eReproductive Period\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ey\u0026thinsp;=\u0026thinsp;0.012x\u0026thinsp;+\u0026thinsp;8.04\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.98\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;0.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eProlongs with increased N\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePre-Reproductive Period\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ey = -0.007x\u0026thinsp;+\u0026thinsp;8.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.78\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;0.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eDecreases with increased N\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePost-Reproductive Period\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ey\u0026thinsp;=\u0026thinsp;0.01x\u0026thinsp;+\u0026thinsp;1.34\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.98\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;0.01\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eIncreases with increased N\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLongevity\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ey\u0026thinsp;=\u0026thinsp;0.016x\u0026thinsp;+\u0026thinsp;18.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.93\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;0.001\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003ePositively influenced by N\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eLife Table Parameters Regression Analysis\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eParameter\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eRegression Equation\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eR\u0026sup2;\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003ep-value\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eInterpretation\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNet Reproductive Rate (R\u003csub\u003e0\u003c/sub\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ey\u0026thinsp;=\u0026thinsp;0.09x\u0026thinsp;+\u0026thinsp;29.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.90\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eHigher nitrogen enhances fecundity\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eIntrinsic Rate of Increase (r)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ey\u0026thinsp;=\u0026thinsp;0.007x\u0026thinsp;+\u0026thinsp;0.20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.94\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eAccelerated population growth\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFinite Rate of Increase (λ)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ey\u0026thinsp;=\u0026thinsp;0.009x\u0026thinsp;+\u0026thinsp;1.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.94\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003ePositively correlated with N\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMean Generation Time (T)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ey = -0.02x\u0026thinsp;+\u0026thinsp;14.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.90\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eShortened with increased N\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDoubling Time (Dt)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ey = -0.006x\u0026thinsp;+\u0026thinsp;3.03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.93\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eDeclines with higher N levels\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eNitrogen levels within the host plant significantly influence various aspects of aphid biology, including development rate, physical characteristics, life history traits, and the proportional production of winged versus wingless morphs (Dixon, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e1987\u003c/span\u003e). Host plant nitrogen concentration significantly influences aphid reproductive patterns and seasonal population dynamics, altering both the timing and intensity of their reproductive cycles throughout the year (Dixon et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e1993\u003c/span\u003e). Our study confirmed that nitrogen availability exhibited significant positive impacts on multiple demographic parameters of aphid populations. Elevated nitrogen concentrations resulted in prolonged reproductive and post-reproductive phases and shrinks the pre reproductive period of the cabbage aphid, however Increases in nitrogen rates on wheat (in hydroponic culture) did not substantially alter the length of the pre-reproductive phase, the reproductive period, longevity, or the reproductive rate of the Russian wheat aphid, \u003cem\u003eDiuraphis noxia\u003c/em\u003e (Kurdjumov), according to Moon et al. (\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e1995\u003c/span\u003e) but the studies of Zarghami et al (\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2010\u003c/span\u003e) revealed that the nitrogen fertilisation levels positively correlates with cabbage aphid ( \u003cem\u003eBrevicoryne brassicae\u003c/em\u003e ) performance on oilseed rape ( RGS003 cultivar) and reported that a higher level of nitrogen fertilisation resulted in a shorter pre-reproductive phase overall, but it had no discernible effect on lifespan. In agreement to our results Fallahpour et al. (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2015\u003c/span\u003e) observed that aphid developmental periods shortened as nitrogen concentrations increased, demonstrating a significant inverse relationship between host plant nitrogen content and aphid development time. The net reproductive rate (R₀) showed increased linearly trend with the increase of nitrogen fertiliser (, R\u0026sup2; = 0.90, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001), indicating enhanced fecundity with nitrogen enrichment. In our experiment the mean daily fecundity exhibited a distinctive non-linear response pattern with respect to nitrogen concentration, characterized by a saturation plateau at higher nitrogen levels (R\u0026sup2; = 0.86, p\u0026thinsp;\u0026lt;\u0026thinsp;0.002). This asymptotic relationship indicates potential physiological constraints on reproductive output, suggesting diminishing reproductive returns beyond a critical nitrogen threshold. This phenomenon may reflect inherent limitations in the aphid's capacity to convert additional nutritional resources into offspring production once baseline nutritional requirements have been sufficiently met. These findings align with initial observations of enhanced A. gossypii fecundity with nitrogen application on cucumber (Pettit et al. 1994) and cotton (Rosenheim et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e1994\u003c/span\u003e; Nevo and Coll \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2001\u003c/span\u003e). Conversely, nitrogen fertilization showed no impact on reproductive output for \u003cem\u003eA. gossypii\u003c/em\u003e on chrysanthemums (Bethke et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e1998\u003c/span\u003e) or \u003cem\u003eD. noxia\u003c/em\u003e on wheat (Moon et al. \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e1995\u003c/span\u003e). Fallahpour et al. (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2015\u003c/span\u003e) also demonstrated increased \u003cem\u003eLipaphis erysimis\u003c/em\u003e fecundity with higher nitrogen levels across three canola cultivars (Zarfam, Okapi, Modena). Excessive nitrogen application (120\u0026ndash;130 kg/acre) in wheat increases aphid infestations despite higher ladybird beetle activity, while moderate nitrogen (90 kg/acre) minimizes pest pressure (Maqsood et al 2025).Comparable fecundity enhancements with elevated nitrogen were documented for Aphis gossypii on cucumber (Hosseini et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2010\u003c/span\u003e) and cotton (Nevo and Coll, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2001\u003c/span\u003e), and for Brevicoryne brassicae on oilseed rape (Brassica napus) (Zarghami et al., \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). Alasvand Zarasvand et al. (2015) observed that the varied amounts of Nitrogen had little effect on pre- and post-reproductive periods but had substantial influence on reproductive period, adult longevity and fecundity of \u003cem\u003eSchizaphis graminum (\u003c/em\u003eRondani). The studies of Eini et al (\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) indicated that the fecundity of A. gossypii decreased with the increasing amount of nitrogen. Furthermore, Aqueel and Leather (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2011\u003c/span\u003e) found nitrogen fertilizer positively affected \u003cem\u003eSitobion avenae\u003c/em\u003e (F) and \u003cem\u003eRhopalosiphum padi\u003c/em\u003e (L) fecundity on wheat plants. Hosseini et al. (2015) observed maximum \u003cem\u003eA. craccivora\u003c/em\u003e Koch reproduction at 100% recommended nitrogen levels with minimum reproduction in unfertilized plants. Hosseini et al. (2014) reported comparable findings for \u003cem\u003eLipaphis erysimi\u003c/em\u003e (Kalt). Khattak et al. (\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e1998\u003c/span\u003e) demonstrated that nitrogen fertilizer applied independently increased Brevicoryne brassicae (L) populations on canola, whereas combined nitrogen and phosphorus applications reduced pest numbers. Concurrently, our results showed that both mean generation time \u003cem\u003e(T)\u003c/em\u003e and population doubling time \u003cem\u003e(Dt)\u003c/em\u003e were found to be inversely proportional to nitrogen availability, facilitating accelerated population growth dynamics. Eini et al (\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) revealed that Nitrogen fertilizer levels significantly influenced mean generation time (\u003cem\u003eT)\u003c/em\u003e and population doubling time (Dt\u003cem\u003e)\u003c/em\u003e of \u003cem\u003eAphis gossypii\u003c/em\u003e on cucumber plant. But according to primary results of Hosseini et al (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2010\u003c/span\u003e) there is no significant effect of increasing nitrogen fertiliser on mean generation time but significant effect on doubling time of the cotton aphid on cucumber plants. Population intrinsic growth rate (r\u003csub\u003em\u003c/sub\u003e) variations stem primarily from three biological parameters: developmental rate, fecundity, and longevity (Dixon, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e1987\u003c/span\u003e). This metric serves as an essential indicator for quantifying environmental factor effects on population dynamics. Throughout the experiment, the intrinsic rate of increase (r\u003csub\u003em\u003c/sub\u003e) showed strong positive correlations (R\u0026sup2; \u0026gt;0.9, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001) underscore the substantial explanatory power of nitrogen as a predictor variable for aphid population parameters. These results corroborate with previous findings of Hosseini et al. (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2010\u003c/span\u003e) and showed that Nitrogen fertilization significantly influenced the intrinsic rate of natural increase (r\u003csub\u003em\u003c/sub\u003e) of \u003cem\u003eA. gossypii\u003c/em\u003e, with r\u003csub\u003em\u003c/sub\u003e values rising proportionally to nitrogen application rates. Zargami \u003cem\u003eet al\u003c/em\u003e ( 2010) also showed that increase in nitrogen fertilization levels on oilseed rape plants resulted in increase in r\u003csub\u003em\u003c/sub\u003e of \u003cem\u003eBrevicoryne brassica\u003c/em\u003ee. Nevo and Coll (\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2001\u003c/span\u003e) similarly demonstrated that elevated nitrogen fertilization in cotton systems corresponds with increased intrinsic growth rate (r\u003csub\u003em\u003c/sub\u003e) in \u003cem\u003eA. gossypii\u003c/em\u003e populations. Similarly the studies conducted by Fallahpour et al (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2015\u003c/span\u003e) found that there is a significant positive effect of nitrogen fertiliser on the r\u003csub\u003em\u003c/sub\u003e of aphid and Gao et al (\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2025\u003c/span\u003e) also found that Nitrogen fertilization improved plant growth (height, biomass) and biochemical traits (nitrogen, chlorophyll, tannin), while also enhancing aphid life history parameters (longevity, fecundity, population growth rates) Conversely, Jansson and Smilowitz (\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e1986\u003c/span\u003e) reported diminished \u003cem\u003eMyzus persicae\u003c/em\u003e population growth rates at maximum nitrogen levels on potatoes. Chau et al. (\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2005\u003c/span\u003e) documented increasing A. gossypii population growth on chrysanthemum as nitrogen rates rose from 0 to 38 ppm, followed by stabilization between 38 and 488 ppm. Cole (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e1997\u003c/span\u003e) determined that concentrations of key amino acids\u0026mdash;tyrosine, alanine, leucine, and glutamic acid\u0026mdash;explained 43% of variation in aphid intrinsic growth rates, with elevated tyrosine and glutamic acid levels specifically enhancing aphid performance parameters. These findings align with established phloem-feeding insect nutritional ecology models, wherein host plant nitrogen content directly influences phloem sap compositional quality, particularly amino acid profiles and concentrations. The observed demographic responses likely reflect the physiological mechanisms through which enhanced nutritional substrate availability translates to improved reproductive efficiency and developmental outcomes in aphid populations. The magnitude of these effects suggests that nitrogen may function as a primary limiting factor in aphid population growth within agricultural and natural ecosystems.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis study underscores the profound ecological impact of nitrogen fertilization on the population dynamics of \u003cem\u003eBrevicoryne brassicae\u003c/em\u003e. Nitrogen-enriched kale plants enhanced aphid longevity, reproduction, and developmental rates, resulting in a faster generational turnover. These improvements can be attributed to the enhanced nutritional quality of host plants, particularly the increased availability of nitrogen-rich phloem sap, which likely made them more palatable and nutritious for the aphids. Extended lifespan allowed aphids to reproduce over a longer period, thereby increasing total offspring and supporting larger populations. A prolonged reproductive phase further amplified reproductive success, while a longer post-reproductive lifespan indicated better overall vitality and health of aphids on nitrogen-rich plants. Furthermore, a shorter pre-reproductive period demonstrated faster development to reproductive maturity, which accelerated population establishment and growth. The observed increase in fecundity and net reproductive rate (R₀) indicates enhanced energy availability for reproduction due to better host plant nutrition. Moreover, the rise in intrinsic rate of increase (r) and finite rate of increase (λ) with nitrogen reflects both higher reproductive output and a faster life cycle, resulting in rapid population multiplication under nitrogen-rich conditions.However, a notable plateau in daily mean fecundity at higher nitrogen concentrations Fig.\u0026nbsp;(1h). suggests a physiological or nutritional threshold beyond which further increases in nitrogen do not translate into proportional reproductive gains. This threshold effect may reflect limitations in nutrient assimilation or the biological capacity of aphids. Similarly, a reduction in generation time (T) and doubling time (D\u003csub\u003et\u003c/sub\u003e) under increased nitrogen conditions points to quicker generational turnover and faster population doubling\u0026mdash;critical factors in pest outbreaks. Collectively, the evidence indicates that nitrogen is a key driver of aphid population dynamics, enhancing nearly all life table parameters. While nitrogen supports crop growth, excessive fertilization poses a risk of pest escalation, particularly for sap-feeding insects like \u003cem\u003eB. brassicae\u003c/em\u003e. Therefore, strategic nitrogen management is crucial not only for optimizing plant health and productivity but also for mitigating pest outbreaks as part of integrated pest management (IPM) strategies.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003ch2\u003eConflict of interest:\u003c/h2\u003e\u003cp\u003eThe author confirms that there are no known financial or personal conflicts that could have influenced the work reported in this manuscript.\u003c/p\u003e\u003c/p\u003e\u003ch2\u003eFunding:\u003c/h2\u003e\u003cp\u003eThe author gratefully acknowledges financial support from the Council of Scientific and Industrial Research \u0026ndash; Human Resource Development Group (CSIR-HRDG), New Delhi, India [File No. / Grant No. 09/0251(17624)/2024-EMR-I].\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eAuthors contribution Title of Manuscript: Forecasting life table parameters of Cabbage Aphid Brevicoryne brassica (L.)Hemiptera: Aphididae using differential Nitrogen-regimes in kale Corresponding Author1\u0026bull;Full Name: Dr. Anisa Ayub\u0026bull;Affiliation: Department of Zoology, university of Kashmir [Srinagar , jammu and Kashmir , India \u0026bull;Email: [ [email protected] ]\u0026bull;ORCID ID:0009-0006-4443-3539\u0026bull;Phone Number: [7006821513l]Corresponding author2 \u0026bull;Full Name: Altaf Hussain Mir \u0026bull;Affiliation: university of Kashmir ]\u0026bull;Email: [email protected]\u0026bull;Contribution: Statistical analysis, supervision, and critical revision of the manuscript.Author Contributions\u0026bull;Anisa Ayub: Conceptualisation, experiment design, data collection, interpretation of results, manuscript writing.\u0026bull;Dr. Altaf Hussain Mir: Statistical analysis, model validation, supervision, and manuscript review.AcknowledgementWe thank the Council of Scientific and Industrial Research (CSIR), India, for funding support. We also extend our gratitude to laboratory and greenhouse staff who assisted in maintaining plant and aphid cultures.Funding StatementThe author gratefully acknowledges financial support from the Council of Scientific and Industrial Research \u0026ndash; Human Resource Development Group (CSIR-HRDG), New Delhi, India [File No. / Grant No. 09/0251(17624)/2024-EMR-I].\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eAcknowledgementWe thank the Council of Scientific and Industrial Research (CSIR), India, for funding support. We also extend our gratitude to laboratory and greenhouse staff who assisted in maintaining plant and aphid cultures. We express our sincere thanks to the Head of the Department of Zoology for providing the necessary facilities and encouragement throughout the study.\u003c/p\u003e"},{"header":"References","content":"\u003col class=\"decimal_type\"\u003e\n\u003cli\u003eAlasvand Zarasvand, A., Allahyari, H., \u0026amp; Fattah-Hosseini, S. (2013). 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A comparison of the reproduction of \u003cem\u003eBrevicoryne brassicae\u003c/em\u003e and \u003cem\u003eMyzus persicae\u003c/em\u003e in relation to soluble nitrogen concentration and leaf age (leaf position) in the Brussels sprout plant. \u003cem\u003eEntomologia experimentalis et applicata\u003c/em\u003e, \u003cem\u003e12\u003c/em\u003e(3), 351-364.\u003c/li\u003e\n\u003cli\u003eZarghami, S., Allahyari, H., Bagheri, M. R., \u0026amp; Saboori, A. (2010). Effect of nitrogen fertilization on life table parameters and population growth of Brevicoryne brassicae. \u003cem\u003eBulletin of Insectology\u003c/em\u003e, \u003cem\u003e63\u003c/em\u003e(1), 39-43.\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":"Cabbage aphid, Nitrogen fertilization, Kale (Brassica oleracea var. acephala), Intrinsic rate of increase (rₘ), Net reproductive rate (R₀), Finite rate of increase (λ), Mean generation time (T), Population doubling time, Integrated pest management (IPM)","lastPublishedDoi":"10.21203/rs.3.rs-7863911/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7863911/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe interactions between plants and herbivores are influenced by the increased application of nitrogen to crops, which has the potential to enhance the growth of herbivore populations. This study evaluates the impact of nitrogen fertilization on the life table parameters of cabbage aphid using kale (\u003cem\u003eBrassica oleracea\u003c/em\u003e var. \u003cem\u003eacephala\u003c/em\u003e) as a host plant under controlled greenhouse conditions. Nine nitrogen treatments (ranging from 0% to 200% of the recommended dose) were applied, while other biotic and abiotic factors were kept constant. Aphid performance was assessed based on developmental and reproductive metrics, including pre-reproductive period, reproductive and post-reproductive periods, adult longevity, mean daily fecundity, net reproductive rate (R₀), intrinsic rate of increase (rₘ), finite rate of increase (λ), mean generation time (T), and population doubling time. Linear regression models revealed strong, statistically significant relationships between nitrogen levels and cabbage aphid\u0026rsquo;s life history traits. Increased nitrogen availability extended reproductive and post-reproductive periods, enhanced mean daily fecundity, and reduced the pre reproductive period, mean generation and doubling times, leading to faster population growth. While as the intrinsic rate of increase and net reproductive rate both showed robust positive correlations with nitrogen levels (R\u0026sup2; \u0026gt;0.9, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). These results highlight the critical influence of nitrogen in shaping pest population dynamics and stress the importance of balanced fertilization strategies. Excessive nitrogen application, while promoting plant growth, can inadvertently intensify aphid infestations. The study advocates for integrated pest and nutrient management approaches to sustainably mitigate the pest pressures on kale plant .\u003c/p\u003e","manuscriptTitle":"Forecasting life table parameters of Cabbage Aphid Brevicone brassica (L.)Hemiptera: Aphididae using differential Nitrogen-regimes in kale","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-07 12:51:30","doi":"10.21203/rs.3.rs-7863911/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":"fecef8c4-440f-4d86-9eb6-49a2517b162e","owner":[],"postedDate":"November 7th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-11-28T11:24:01+00:00","versionOfRecord":[],"versionCreatedAt":"2025-11-07 12:51:30","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7863911","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7863911","identity":"rs-7863911","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}