Demography of Cacopsylla chinensis (Hemiptera: Psyllidae) Reared on Four Cultivars of Pyrus bretschneideri (Rosales: Rosaceae) and P. communis Pears With Estimations of Confidence Intervals of Specific Life Table Statistics

Morphotype-Specific Antifungal Defense in Cacopsylla chinensis Arises from Metabolic and Immune Network Restructuring

Pear psylla (Cacopsylla chinensis), a major pear tree pest widely distributed in China, is increasingly affecting the productivity of orchards. This species exhibits seasonal polyphenism with two distinct forms, namely, a summer form and a winter form. Through topically applying Beauveria bassiana conidial suspensions to the abdominal cuticle of C. chinensis, we demonstrated that the entomopathogenic fungus B. bassiana exhibits significant yet phenotypically divergent virulence against these two forms. Using PacBio SMRT sequencing and Illumina RNA-seq, we analyzed transcriptomic changes post-infection, revealing form-specific immune responses, with 18,232 and 5027 differentially expressed genes identified in summer- and winter-form pear psylla, respectively, and a total of 3715 DEGs shared between the two seasonal phenotypes. In summer-form individuals, B. bassiana infection disrupted oxidative phosphorylation and downregulated immune recognition genes, cellular immune-related genes, and signaling genes, along with the upregulation of the immune inhibitor serpin, indicating immunosuppression. Conversely, in winter-form individuals, immune-related genes and glycolytic rate-limiting enzymes were upregulated after infection, suggesting that the winter-form immune system normally responds to B. bassiana infection and supports efficient defense through metabolic reprogramming to fuel energy-demanding defenses. These findings advance our understanding of C. chinensis/B. bassiana interactions, providing a basis for elucidating immune regulation in seasonally polymorphic insects. The results also inform strategies to optimize B. bassiana-based biocontrol, contributing to sustainable pear psylla management.

The biological characteristics and life table parameters of Plodia interpunctella (Lepidoptera: Pyralidae) reared on different maize varieties

The Indianmeal moth, Plodia interpunctella (Hübner) is a major polyphagous pest of stored food products causing serious quantity and quality losses. In this study, the life history of P. interpunctella was evaluated on different maize varieties, including Simon, Valbom, 703, BK, and BC678. The preadult duration for P. interpunctella were 35.5, 43.1, 39.2, 43.4, and 36.8 d on Simon, Valbom, 703, BK, and BC678, respectively. The mean total longevity on Valbom was 52.2 d which was significantly longer than the 41.8 d on Simon (P = 0.012). The developmental period of moths was the most prolonged on Valbom indicating low nutritional suitability of this variety. However, the moths preferred Valbom for oviposition, and more than 132 eggs were laid on this variety. The most intrinsic rate of increase (r) was reported on BC678 and Simon, while the lowest population growth rate was on BK and Valbom. The highest r value on BC678 and Simon could be due to their high moisture and protein content. Based on the shorter preadult, total preoviposition period, mean generation time and higher life table parameters (gross reproductive rate, r, and λ) that occurred on the BC678, make this variety most favorable host for P. interpunctella. The findings highlighted the importance of maize variety selection in managing this pest in stored food products.

Potential influence of supplemental nutrients intake by adults on the development, fecundity, and population growth of Megalurothrips usitatus (Thysanoptera: Thripidae) offspring

Megalurothrips usitatus (Bagnall) (Thysanoptera: Thripidae), is an important pest in cowpea-growing areas of south China. To study control strategies, M. usitatus has been raised for multiple generations in the laboratory. Considering the impact of supplemental nutrients on colony fitness during laboratory rearing is crucial for achieving a significant population of uniformly developed individuals. Here, an age-stage, 2-sex life table for M. usitatus was developed to examine the impacts of F0M. usitatus adults fed on 3 different supplemental diets (20% sucrose solution, 20% pollen solution, and 20% honey solution) on the development, fecundity, and population growth of F1M. usitatus. The findings indicated that, compared to thrips fed on water, F0 adult thrips provided with 3 supplementary diets exhibited a reduction in the developmental duration for each instar, an increase in fecundity, and an extension of the lifespan of F1M. usitatus, with honey yielding the best results. Similarly, the addition of supplemental nutrients resulted in a reduction in the mean generation time (T) and an enhancement of the net reproductive rate (R0), intrinsic rate of increase (r), and finite rate of increase (λ) compared to the control group. The effects were highest for honey, followed by pollen, and then sucrose. This study provides favorable evidence concerning the direct impacts of parental nutrition supplementation on the fitness of offspring in insects, and provides information to aid indoor rearing of M. usitatus.

Sustainable management of potato tuber moth in storages using entomopathogenic fungi and an ectoparasitic mite

BACKGROUND

The potato tuber moth (PTM), Phthorimaea operculella, is an economically important pest of potato crops worldwide. So far, the application of chemical pesticides is the major measure to manage PTM, but it induces serious deleterious impacts on the environment and human health. Here, we screened the entomopathogenic fungi that are lethal to PTM, and tested their sublethal impacts on PTM development, mortality, and reproduction as well as that of ectoparasitic mite Pyemotes zhonghuajia, a natural enemy of PTM.

RESULTS

Among 13 tested entomopathogenic fungal strains in three genera, Beauveria Vuillemin, Cordyceps Fries, and Talaromyces Benjamin, Cordyceps fumosorosea (strain KY1136) and Beauveria bassiana (strain KY1115) caused a significantly higher mortality in PTM eggs, larvae, and pupae. Median lethal concentration (LC50) of both strains prolonged PTM immature development, shortened adult longevity, and reduced fecundity and life table parameters in terms of intrinsic rate of increase (rm), net reproductive rate (R0), and finite rate of increase (λ). The LC50 value of KY1136 (1.9 × 106 spores/mL) was lower than that of KY1115 (9.0 × 106 spores/mL), indicating the greater potential for biological control of PTM by KY1136. Both strains had no significant impact on P. zhonghuajia survival and reproduction. Increasing P. zhonghuajia density reduced PTM feeding and pupation rate, while the combined application of P. zhonghuajia and entomopathogenic fungi had no additional effect in inhabiting PTM feeding and pupation.

CONCLUSION

Entomopathogenic fungal strains Cordyceps fumosorosea KY1136 and Beauveria bassiana KY1115 are the potential biological control agents of PTM, but do not impose a negative impact on the natural enemy. Our study provides insights into the integrated pest management of PTM by combining the entomopathogenic fungi and an ectoparasitic mite. © 2024 Society of Chemical Industry.

Grafting Tomato 'Nairouz F1' onto Interspecific Hybrids for Induced Antibiosis and Antixenosis Resistance to Tetranychus urticae Koch via Chlorogenic Acid Synthesis

BACKGROUND

This study is the first research to investigate the potential of grafting to induce tomato resistance to two-spotted spider mite (TSSM), Tetranychus urticae Koch. TSSM can cause up to 50% yield loss of tomato. The grafting technique permits the rapid adoption of biotic/abiotic stress resistance/tolerance from wild relatives as rootstock while preserving the scion's important horticultural characteristics. Although TSSM resistance is found in wild tomato relatives, particularly those with the Mi-1 gene, its effects as rootstocks on TSSM resistance remain uncertain. Tomato 'Nairouz F1' (lacking Mi-1) grafted onto six interspecific hybrids with Solanum habrochiates (harboring Mi-1/mi-1), including commercial rootstock 'Estamino' and 'Fortamino', along with hybrids between tomato 'VFN-14' and each of S. habrochiates AusTRCF312064 (R312064), AusTRCF312344 (R312344), CGN15391 (R15391), and LA1777 (R1777). In the 2019 and 2020 fall seasons, the grafted and ungrafted plants were assessed in a naturally TSSM-infested field. The population of TSSM movable stages on grafted and ungrafted plants was estimated one week after transplanting, and every two weeks for 11 weeks. To assess antixenosis and antibiosis resistance in tomato grafts, TSSM males and females were reared on leaves of grafts onto R312064 and R15391, along with ungrafted plants. TSSM bio-behaviors and two-sex life table parameters were assessed.

RESULTS

Grafting onto interspecific hybrids, particularly R15391, R312064, and R312344, significantly lowered TSSM populations compared to commercial rootstocks and ungrafted plants. HPLC analysis revealed that grafting induced foliar synthesis of herbivore-repellent (antixenosis) and antibiosis phenolics, viz., chlorogenic acid in all grafts and syringic acid, pyrocatechol, and vanillin in certain grafts. Grafts-R312064 showed delayed TSSM development, lower survival rates, lower fecundity, and higher mortality. Grafts-R312064 also had a longer mean generation time (GT; 23.33 days) and a lower reproductive rate (R0: 14.63), leading to a slower intrinsic population growth rate (rm: 0.115) compared to ungrafted plants and grafts-R15391.

CONCLUSION

The findings suggest tomato grafting onto rootstocks with the Mi-1 gene, particularly R312064, could reduce TSSM populations through induced antixenosis and antibiosis resistance mechanisms.

The Effects of Temperature on Development, Reproduction, Population Dynamics and Protective Enzyme Activity of Neotoxoptera formosana (Hemiptera: Aphididae)

Neotoxoptera formosana is an allium vegetable pest that has increasingly threatened Chinese leek production in North China in recent years. The effects of temperature on the biological characteristics and physiology of N. formosana are not well understood. In this study, life tables were constructed at 12 °C, 16 °C, 20 °C, 24 °C, and 28 °C to explore the effects of temperature on the development, reproduction, and population dynamics of N. formosana, and to determine the threshold temperature (C) and the effective cumulative temperature (K) for each developmental stage of this aphid. The protective enzyme activity of N. formosana at three representative temperatures, 12 °C, 20 °C, and 28 °C, was determined to explore the physiological response of N. formosana to temperature. The result showed that the increasing temperature speeded up the development of N. formosana, but decreased the body size, and shortened the longevity and reproduction period of adults. The temperature exceeding 20 °C inhibited its reproduction. The N. formosana population was obviously inhibited by 28 °C with all the population parameters decreasing to be the lowest, especially the fecundity, which was 16.7 times lower than that at 20 °C. The population expanded the fastest at 20 °C, followed by 24 °C, 16 °C, and 12 °C, the slowest at 28 °C, with the population size merely increasing to 2.3 times at 60 days. The K values for the first, second, third, and fourth-instar nymphs were 1.852 °C, 5.029 °C, 4.747 °C and 5.979 °C, respectively, and the C values were 47.540 days °C, 30.817 days °C, 33.481 days °C and 32.294 days °C, respectively. The C value for nymphal aphids was 4.002 °C, and the K value was 145.252 days °C. The activity of superoxide dismutase and peroxidase of N. formosana at 28 °C was higher than at 12 °C and 20 °C, and the catalase activity of N. formosana was highest at 12 °C. In conclusion, the temperature had significant effects on population parameters and the physiological metabolism of N. formosana.

Impact of temperature on development and reproduction of the olive black scale Saissetia oleae (Olivier) (Hemiptera: Coccidae)

The olive black scale, Saissetia oleae (Olivier), is a significant pest of olive crops worldwide. The developmental, reproductive, and population growth parameters of S. oleae were evaluated under five constant temperature conditions (18°C to 33°C). Developmental durations significantly decreased with increasing temperatures. Female lifespan decreased from 161.6 days at 18°C to 104.3 days at 33°C, while male lifespan decreased from 96.8 days at 18°C to 49.4 days at 33°C. The highest sex ratio (proportion of females) of 0.35 was observed at 30°C, with pre-adult survival rates of 63%, while survival rates dropped to 28% at 18°C. Parthenogenesis was not observed in females. The total pre-oviposition and post-oviposition periods decreased with increasing temperature, with the longest oviposition period at 33°C (49.6 days). Maximum fecundity was recorded at 33°C (379.0 eggs/female), followed by 30°C (298.6 eggs/female), and decreased sharply at 18°C (90.1 eggs/female). The intrinsic rate of increase (r) was highest at 30 and 33°C (0.038 d⁻1), while the net reproductive rate (R0) peaked at 30°C (104.5 offspring/female). The predicted fecundity of the next generation showed significant potential growth at 27 and 30°C, with the population increasing 65.3 times at 30°C and 39.4 times at 27°C. The developmental threshold for S. oleae was highest for first-instar nymphs (7.58°C), while second-instar nymphs had lower thresholds (1.09-1.65°C), with total pre-adult development requiring 1250 degree-days for both males and females. These findings underscore the significant impact of temperature on the development and reproduction of S. oleae, with implications for pest management in olive orchards.

Implications of cyantraniliprole sublethal doses on the population dynamics and gene expression of Aphis gossypii Glover (Hemiptera: Aphididae)

Cyantraniliprole (CYA), widely recognized as a highly effective solution, is widely used in pest management. It has been broadly utilized to manage diverse pests, among which Aphis gossypii Glover (Hemiptera: Aphididae) is a prominent agricultural pest that leads to significant crop damage worldwide. Studies suggest that the sublethal effect of insecticides might contribute to the resurgence of A. gossypii. Therefore, in this study, A. gossypii were exposed to sublethal doses of CYA (LC15 and LC30 values of 1.43 and 2.93 mg/L, respectively) for 48 h then employed life table parameters and RT-qPCR were used to estimate the sublethal and cross-generational impacts. Treatments with sublethal doses of CYA notably reduced the survival and reproduction of the F0A. gossypii and CYA at LC30 significantly increased the fecundity and population growth parameters (R0, r, λ, and GRR) of F1 and reduced in the pre-adult stage. Furthermore, gene expression analysis indicated a significant downregulation of juvenile hormone-binding protein (JHBP) in F0. Conversely, the F1 generation exhibited an upregulation of vitellogenin (Vg), insulin receptor substrate 1 (InS1), ecdysone receptor (EcR), and ultraspiracle protein (USP). The funding not only enhance the comprehension of the sublethal effects of CYA on A. gossypii but also provide valuable guidance for the effective utilization of insecticides in managing the pest.

Survival, development, and reproduction of Aulacorthum solani (Hemioptera: Aphididae) fed on Persicaria lapathifolia

The foxglove aphid, Aulacorthum solani (Kaltenbach), is a polyphagous economic pest. In this study, A. solani were fed on detached leaves of dockleaf knotweed, Persicaria lapathifolia (L.) Delarbre. Survival, development, and reproduction were studied at constant temperatures of 17, 20, 23, 26, 29, and 32 °C. These data were compared with those of controls fed on Glycines max (L.) Merrill. At 17, 20, 23, and 26 °C, the survival rate of A. solani adults fed on P. lapathifolia were lower than those fed on G. max; the adult longevity, aphid total longevity, and reproduction period were shorter. At 20, 23, and 26 °C, the adult fecundity, intrinsic rate of increase, finite rate of increase, and net reproductive rate of A. solani fed on P. lapathifolia were smaller than those fed on G. max. At 29 °C, the survival rate of A. solani adults fed on P. lapathifolia were higher than those fed on G. max; the adult longevity and aphid total longevity were longer. These results are consistent with our finding that A. solani feed on P. lapathifolia, which is important for studying the host adaptability of A. solani.

Transgenerational effects of imidacloprid on Sclerodermus alternatusi (Hymenoptera: Bethylidae) based on age-stage, two-sex life table

Imidacloprid is a widely used insecticide for controlling piercing-sucking pests. However, its impact on nontarget insects must not be ignored. In this study, we assessed the effects of sublethal dose of imidacloprid on Sclerodermus alternatusi (Hymenoptera: Bethylidae), which is an important predator of many pests. The data indicate that imidacloprid at LD10 (0.1468 ng active ingredient per insect) and LD30 (0.2376 ng active ingredient per insect) significantly reduced the longevity and fecundity of the F0 generation of S. alternatusi. However, the adult female longevity of the F1 generation of the LD10 dose group showed a significant increase, and the LD30 dose group showed a nonsignificant increase. The study found that as the imidacloprid dose increased, the intrinsic rate of increase (r) decreased, while the mean generation time (T) increased. The imidacloprid groups also showed a decrease in age-stage specific survival rate (Sxj) and age-specific survival rate (lx). However, the female age-specific survival rate (fx4) showed an increasing and then decreasing trend for all treatments. The study found that imidacloprid had an impact on the longevity of S. alternatusi in the F0 generation and extended the mean generation time (T) in the F1 generation. However, it had negative effects on population growth parameters. These findings can be used as a basis for developing integrated pest management strategies.

The impacts of climate change on the potential distribution of Cacopsylla chinensis (Hemiptera: Psyllidae) in China

Cacopsylla chinensis is an oligophagous pest and has become one of the main pests that cause yield loss in commercial pear orchards in China. Predicting the impact of climate change on the distribution range of C. chinensis is crucial for its effectively preventing and managing. In this study, we collected 102 geographic distribution information of C. chinensis with 8 selected crucial environmental variables to simulate its potential suitable habitats. On this basis, the parameter-optimized maximum entropy model was utilized to predict the potential effect of future climate variation on its distribution, considering various socio-economic pathway scenarios and 3 Earth system models. The findings showed that the current total potential suitable area for C. chinensis was 578.29 × 104 km2, which accounts for 60.24% of China's territory. In the total area, the suitability areas of low, medium, and high were 308.21 × 104 km2, 118.50 × 104 km2, and 151.58 × 104 km2, respectively. Among them, the high suitability areas are mainly distributed in Anhui, Beijing, Chongqing, Hebei, Henan, Hubei, Jiangsu, Liaoning, Shandong, Shanxi, Shaanxi, Sichuan, and Tianjin. Furthermore, our predictions suggest that the potentially suitable areas for this pest will increase by 8.49-35.02% under various future climate change conditions in China. The findings will be propitious to understand the linkage between C. chinensis niches and the relevant environment. It also provides valuable insights for developing future pest management strategies.

Adaptability Analysis of Tuta absoluta to Different Hosts and Related Salivary Genes Identification

Tuta absoluta is a significant agricultural pest primarily affecting Solanaceae plants, resulting in substantial economic losses in agriculture. Insect saliva is an intermediary between insects and plants, playing a crucial role in modulating host adaptability and plant defense. This study analyzed the adaptive differences of T. absoluta on four plants using the two-sex life table method. Results indicated that the host adaptability of T. absoluta to tobacco is worse than its adaptability to the other three varieties of tomatoes. The salivary gland transcriptome analysis and signal peptide prediction revealed that Trypsin, B5 V51-1498, and Ta74 were highly expressed in the salivary glands of T. absoluta subjected to tobacco treatment and exhibit the characteristics of secretory proteins, alongside significant feeding selection differences. Our findings elucidate the adaptive strategies of T. absoluta larvae on various Solanaceae plants and offer new insights into the salivary protein-mediated plant defense processes.

Sublethal effects of flonicamid on the population growth of the grain aphid Rhopalosiphum padi (L.) (Hemiptera: Aphididae)

Rhopalosiphum padi is an important grain pest, causing severe losses during crop production. As a systemic insecticide, flonicamid can control piercing-sucking pests efficiently. In our study, the lethal effects of flonicamid on the biological traits of R. padi were investigated via a life table approach. Flonicamid is highly efficiently toxic to R. padi, with an LC50 of 9.068 mg L-1. The adult longevity and fecundity of the R. padi F0 generation were markedly reduced under the LC25 and LC50 concentrations of flonicamid exposure. In addition, negative transgenerational effects on R. padi were observed under exposure to lethal concentrations of flonicamid, with noticeable decreases in the reproductive period, adult longevity, total longevity, and total fecundity of the F1 generation under the LC25 concentration of flonicamid. Furthermore, the third nymph stage (N3), preadult stage, duration of the adult pre-reproductive period, duration of the total pre-reproductive period, reproductive period, adult longevity, total longevity, and total fecundity of the F1 generation were significantly lower under treatment with the LC50 concentration of flonicamid. The life table parameters were subsequently analysed, revealing that the intrinsic rate of increase (rm) and the net reproductive rate (R0) were significantly lower but that the finite rate of increase (λ) and the mean generation time (T) were not significantly different under the LC25 and LC50 concentrations of flonicamid. These data are beneficial for grain aphid control and are critical for exploring the role of flonicamid in the integrated management of this key pest.

Effects of continuous and transgenerational rearing in peanut leaves on the performance and enzyme activity of Spodoptera frugiperda (Lepidoptera: Noctuidae)

The invasive fall armyworm (FAW), Spodoptera frugiperda, is a polyphagous pest that significantly threatens crops worldwide. FAW may undergo adaptation, enhancing its ability to infect specific plant hosts. However, there is limited knowledge on this topic. After 8 generations of constant rearing on peanut leaves, the performance and enzyme activities of FAW were investigated in this study. Compared to FAW fed on the peanut cultivars 'Fuhua 8' and 'Quanhonghua 1' for 2 generations, those grown on leaves for 5 to 8 generations had significantly shorter pre-adult development times and total preoviposition periods. Fecundity also increased significantly, resulting in an overall improvement in population fitness as measured by demographic parameters. However, the F2 generation of FAW fed on corn leaves outperformed the F8 generation of FAW fed on peanut leaves. In the F2 generation, the FAW peanut population exhibited 30-55% supernumerary larval molts, which decreased substantially in the F5 and F8 generations. Notably, supernumerary larval molts displayed pupation and emergence rates comparable to normal larvae, regardless of the peanut cultivar or rearing generation. The activities of lipase and acetylcholinesterase increased significantly from the F2 to F8 generations, showing substantial negative and positive correlations with larval development time and fecundity, respectively. In conclusion, FAW demonstrated inferior performance on peanut leaves compared to corn leaves, despite its performance was significantly improved after 5 to 8 generations of acclimation. These results suggest that corn will continue to be the primary target crop for FAW in China.

Population Dynamics and Nutritional Indices of Spodoptera frugiperda (Lepidoptera: Noctuidae) Reared on Three Crop Species

The fall armyworm (FAW) is an invasive pest that has been rapidly spreading across China since its detection in Yunnan province in January 2019. Although sugarcane and sorghum have been reported as hosts, their effects on FAW's population growth and life table parameters have not been examined in China. Our research shows that FAW's development and life table metrics vary significantly when reared on sorghum, sugarcane, and maize. Notably, the preadult stage, adult preoviposition period, and total preoviposition period of FAW were markedly longer on sugarcane and sorghum compared to maize. FAW reared on these two crops also exhibited reduced survival rates, pupal weight, fecundity, and lower female-to-male ratios. The study highlights that FAW had lower population growth rates, reproductive rates, and longer generation times on sugarcane and sorghum compared to maize. The consumption index and digestibility index were higher on maize, while conversion efficiency and growth rate were greater on sorghum. Although maize is the most favorable host, FAW can still survive and reproduce on sugarcane and sorghum during the nongrowing season, posing a risk to economically important crops in China. Despite being less favorable for population growth, sugarcane and sorghum still support FAW development and spread. Therefore, enhanced surveillance and early warning measures for sugarcane and sorghum are recommended to monitor FAW population dynamics and mitigate its potential impact on primary host plants.

Integrated Metabolomic and Transcriptomic Profiling Reveals the Defense Response of Tea Plants (Camellia sinensis) to Toxoptera aurantii

The tea plant (Camellia sinensis) is a unique beverage crop worldwide, but its yield and quality are adversely affected by Toxoptera aurantii. However, the response mechanisms of tea plants to T. aurantii stress remain poorly known. Herein, we present the life table of T. aurantii on resistant (W016) and susceptible (HJY) tea cultivars, demonstrating that the fitness of T. aurantii on W016 was lower than that on HJY. Integrated metabolic and transcriptomic analyses revealed that T. aurantii feeding activated pathways associated with phenylpropanoid biosynthesis, plant hormone signal transduction, and ATP-binding cassette (ABC) transporters. Notably, T. aurantii feeding significantly upregulated the levels of brassinolide and p-coumaryl alcohol in W016 but not in HJY. Furthermore, in vitro enzymatic assays indicated that C. sinensis cinnamyl alcohol dehydrogenase (CsCAD1) catalyzes the formation of p-coumaryl alcohol participation in lignin synthesis. Our findings highlight the role of brassinolide-mediated lignin biosynthesis of the tea plant in response to T. aurantii feeding.

An evaluation of the growth, development, reproductive characteristics and pest control potential of three Trichogramma species on Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae)

BACKGROUND

Tuta absoluta is an invasive alien species that has caused major losses in the Chinese tomato industry. Investigating the growth, development, reproduction and pest control effects of three native species of Trichogramma species on the eggs of T. absoluta could provide an ecological tool for preventing and controlling T. absoluta in China. In this study, we constructed age-stage two-sex life tables for three common species of Trichogramma and determined their relative abilities to control T. absoluta in greenhouse insect cages, thus allowing us to identify the species with the most effective ability to prey on T. absoluta eggs.

RESULTS

Analysis showed that the net reproductive rate (R0), gross reproduction rate (GRR) and intrinsic rate of increase (r) of Trichogramma ostriniae were the highest of the three species at 22.85, 32.58 and 1.31, respectively. In the presence of 10 eggs and under ideal conditions, T. ostriniae, Trichogramma chilonis, and Trichogramma dendrolimi produced 9451.04, 5199.56, and 1902.95 offspring, respectively. Following the release of T. ostriniae, tomato leaves incurred a damage index of 1 after the first week, while the number of T. absoluta reduced to 24.60 individuals by week 10 (8.75% of the control treatment).

CONCLUSION

Of the three species of Trichogramma tested in this study, T. ostriniae exhibited the best growth, development, reproductive capacity and predatory ability against T. absoluta, and has broad application prospects. © 2024 Society of Chemical Industry.

Age-Stage, Two-Sex Life Table Analysis of Riptortus pedestris (Hemiptera: Alydidae) Across Different Soybean Varieties

Riptortus pedestris (Hemiptera: Alydidae) is an economically important pest of soybeans, significantly affecting their quality and market value. This study aims to evaluate the adaptability of R. pedestris to different soybean varieties and provide a foundation for selecting resistant varieties and developing effective integrated pest management strategies. Seven widely planted varieties (Beidou No. 3, Jiyu 47, Jiyu No. 80, Jiyu No. 90, Jiyu 203, Kangxianchong No. 6, and Kangxianchong 12) were selected for testing, and the developmental and population parameters of R. pedestris were measured using an age-stage, two-sex life table method. Notable differences were found in the developmental period, female longevity, and total preoviposition period (TPOP) of R. pedestris across diverse varieties. For those feeding on Kangxianchong 12, the nymph stage (14.73 ± 0.11 days), total longevity (37.35 ± 1.12 days), total female longevity (38.83 ± 1.80 days), and fecundity (38.86 ± 3.27 eggs per female) were all remarkably longer than on the other varieties. Additionally, the intrinsic rate of increase (r), finite rate of increase (λ), net reproductive rate (R0), and average generation time (T) of R. pedestris varied significantly between soybean varieties. The lowest r (0.0789 ± 0.0075 per day) and λ (1.0821 ± 0.0081 per day) values were recorded for Kangxianchong No. 6, while the highest were for Jiyu 47 (r = 0.0933 ± 0.0070 per day, λ = 1.0978 ± 0.0076 per day). The R0 and T values for R. pedestris on Kangxianchong 12 (R0 = 16.33 ± 3.24 offspring per female, T = 31.18 ± 0.79 days) were remarkably higher than those of the other six varieties, suggesting that Kangxianchong 12 and Jiyu 47 are preferred hosts, whereas Kangxianchong No. 6 is less preferred. These results provide valuable insights for optimizing soybean cultivation and managing R. pedestris.

The Changes in Cross-Resistance, Fitness, and Feeding Behavior in Aphis gossypii as Their Resistance to Sulfoxaflor Declines

The increasing resistance in Aphis gossypii field populations to sulfoxaflor and many different types of insecticides represents a significant challenge in protecting cotton production in China. Although resistant pests were able to regain their susceptibility to insecticides after the reduction in insecticide applications, some of their biological parameters remained different from susceptible strains. The resistance to sulfoxaflor was unstable in A. gossypii after the loss of selective pressure. The strain with declined resistance (Sul-D) (RR = 1.11-fold) restored its susceptibility to sulfoxaflor, acetamiprid, and imidacloprid after the sulfoxaflor-resistant (Sul-R) (RR = 51.57-fold) was maintained without insecticide pressure for 22 generations. Sul-R had a relative fitness of 0.87, and the Sul-D strain still had a relative fitness of 0.84, even if its susceptibility to sulfoxaflor was restored. Compared with the susceptible strain (Sus), the Sul-R and Sul-D strains became more active in searching for appropriate feeding positions because they generated more intercellular apoplastic stylar pathway events (C). However, the phloem-feeding ability was reduced in the Sul-R and Sul-D strains, as shown by the decrease in phloem behavioral parameters, such as phloem salivations (E1), phloem ingestion (E2), and the percentages of E1 and E2. The negative hormesis effect of sulfoxaflor on phloem feeding was observed in susceptible strain but not in Sul-R and Sul-D, as evidenced by the significant decreases in the number of E1, the duration of E1 and E2, and the percentage of E1 and E2 in the Sus strain. Sulfoxaflor resistance was unstable in A. gossypii, and there was still a fitness cost to A. gossypii after recovering susceptibility to sulfoxaflor. The phloem-feeding ability was reduced in the Sul-R and Sul-D strains compared with the Sus strain, but the negative hormesis effect of sulfoxaflor on phloem feeding was only found in the Sus strain. The outcomes of this study could contribute to a comprehensive risk assessment and provide a basis for developing a better strategy to control A. gossypii.

Neuropeptide Bursicon and its receptor-mediated the transition from summer-form to winter-form of Cacopsylla chinensis

Seasonal polyphenism enables organisms to adapt to environmental challenges by increasing phenotypic diversity. Cacopsylla chinensis exhibits remarkable seasonal polyphenism, specifically in the form of summer-form and winter-form, which have distinct morphological phenotypes. Previous research has shown that low temperature and the temperature receptor CcTRPM regulate the transition from summer-form to winter-form in C. chinensis by impacting cuticle content and thickness. However, the underling neuroendocrine regulatory mechanism remains largely unknown. Bursicon, also known as the tanning hormone, is responsible for the hardening and darkening of the insect cuticle. In this study, we report for the first time on the novel function of Bursicon and its receptor in the transition from summer-form to winter-form in C. chinensis. Firstly, we identified CcBurs-α and CcBurs-β as two typical subunits of Bursicon in C. chinensis, which were regulated by low temperature (10 °C) and CcTRPM. Subsequently, CcBurs-α and CcBurs-β formed a heterodimer that mediated the transition from summer-form to winter-form by influencing the cuticle chitin contents and cuticle thickness. Furthermore, we demonstrated that CcBurs-R acts as the Bursicon receptor and plays a critical role in the up-stream signaling of the chitin biosynthesis pathway, regulating the transition from summer-form to winter-form. Finally, we discovered that miR-6012 directly targets CcBurs-R, contributing to the regulation of Bursicon signaling in the seasonal polyphenism of C. chinensis. In summary, these findings reveal the novel function of the neuroendocrine regulatory mechanism underlying seasonal polyphenism and provide critical insights into the insect Bursicon and its receptor.

A comparative approach for life history and functional response demonstrates similar survival strategies for Trichogramma evanescens and T. pintoi

BACKGROUND

Egg parasitoids are important biological control agents of lepidopteran pests of agricultural crops. Trichogramma evanescens Westwood and T. pintoi Voegele (Hymenoptera: Trichogrammatidae) are egg parasitoids with worldwide importance. The parasitoid selection necessitates comparative assessment of the life table traits and functional response analysis to provide insights into their effectiveness in pest control. In this study, we examined their life table traits including survivorship and reproductivity, and functional response and associated parameters i.e., attack coefficient and handling time.

RESULTS

Life table parameters, using age-stage, two-sex theory, revealed similar survival and reproductive strategies for both species. For example, the female longevity, oviposition days and fecundity did not differ between both species. Exceptionally, the male longevity of T. evanescens was shorter than that of T. pintoi. The population growth parameters such as gross reproductive rate (GRR), net reproductive rate (R0), intrinsic rate of increase (r), finite rate of increase (λ), and mean generation time (T) did not differ between species. The polynomial logistic regression yielded a type III functional response and a non-linear least square analysis revealed different attack coefficient and similar handling time. However, their parasitism rate differed between the lowest (five eggs) and highest (80 eggs) initial host egg densities such that T. evanescens had a lower parasitism rate at the lowest density and higher parasitism rate at the highest density.

CONCLUSION

The similarity in survival strategies and minor differences in host handling of both parasitoids are discussed in terms of relevance to applied biological control applications and evolutionary traits. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Adaptability of the Soybean Aphid Aphis glycines (Hemiptera: Aphididae) to Temperature and Photoperiod in a Laboratory Experiment

The soybean aphid, Aphis glycines Matsumura, 1917, is a crucial soybean pest. Cultivated soybean, Glycine max (Carl von Linné) Elmer Drew Merrill, 1917, and wild soybean, Glycine soja Philipp Franz von Siebold & Joseph Gerhard Zuccarini, 1843, are summer hosts of A. glycines. In this study, the development, reproduction, and morphogenesis of A. glycines fed wild soybean (AgFW) were studied at different temperatures and photoperiods. The data were compared with that of A. glycines fed soybean (AgFS). At 20-29 °C, the adult lifespan of the first-third-generation AgFW was shorter than or equal to that of AgFS. Significant differences existed in the adult fecundity and intrinsic rate of increase between AgFW and AgFS. At a 10L:14D h photoperiod, males of AgFW were deposited earlier than, or as early as, males of AgFS. At 17 °C, the gynoparae of AgFW were deposited in proportions greater than or equal to those of AgFS. Based on these results, we concluded that the adaptability of AgFW and AgFS to temperature and photoperiod significantly differs. It is important to understand the life cycle of A. glycines in Harbin, northeast China, and formulate an integrated pest management strategy for A. glycines in the region.

Life history parameters of Ectropis grisescens (Lepidoptera: Geometridae) in different Wolbachia infection states

Wolbachia, a prevalent intracellular symbiotic bacterium in insects, plays a significant role in insect biology. Ectropis grisescens (Warren; Lepidoptera: Geometridae) is a devastating chewing pest distributed in tea plantations throughout China. However, it is unclear how Wolbachia titers affect the fitness and reproduction of E. grisescens. In this study, the impacts of 3 different infection lines, naturally Wolbachia-infected, Wolbachia-uninfected, and Wolbachia transinfected, regarding the life history traits of E. grisescens, were evaluated using the age-stage, 2-sex life table. Wolbachia infection shortened preadult duration and preoviposition periods and increased the fecundity, net reproductive rate, and finite rate of increase. Meanwhile, population projection indicated that E. grisescens population size with Wolbachia infection can increase faster than without. These results indicate that Wolbachia plays a regulatory role in the fitness of E. grisescens. It is also noted that the life history parameters of E. grisescens may positively correlate with Wolbachia titers. These findings could aid in pest management in tea gardens.

Evaluating the effects of short-term low temperature on the growth and development of Trichopria drosophilae based on the age-stage two-sex life table

BACKGROUND

The effects of low temperatures on parasitic wasps are crucial for maintaining farmland biodiversity and enhancing biological control, especially given the implications of global warming and frequent extreme cold events.

METHODS

We studied the effects of different low temperatures (-8 ± 1 °C, -4 ± 1 °C, 0 ± 1 °C, 4 ± 1 °C, and 8 ± 1 °C) on the mating frequency and duration of male adults of Trichopria drosophilae and the number of pupae beaten by female adults, and constructed the age-stage two-sex life table of T. drosophilae.

RESULTS

This study found that male T. drosophilae adults exposed to low temperatures for 12 h significantly altered their mating behavior, peaking between 15:00 and 17:00. As the temperature dropped during the exposure, both the mating frequency of T. drosophilae and the duration of pupal beating were affected. The survival rate of female adults dropped from 39.55% at 8 °C to just 21.17% at -8 °C. Low-temperature treatment shortened the development period and lifespan for T. drosophilae adults. They developed 4.71 days faster and had a total lifespan that was 10.66 days shorter than those in the control group after being exposed to -8 °C. Furthermore, the average number of eggs laid by females at -8 °C was 4.46 less than that at 8 °C and 6.16 less than that in the control group, which laid an average of 21.55 eggs. The net reproductive rate (R0) of T. drosophilae decreased with lower temperatures, reaching a low of 23.64 at -8 °C. Conversely, the intrinsic growth rate (rm) actually increased as temperatures dropped, with the lowest value being 0.21 at -8 °C.

CONCLUSIONS

The findings indicate that short-term exposure to low temperatures hampers the growth and population increase of T. drosophilae, thereby reducing their effectiveness as biological control agents.

Nanoparticle-mediated calmodulin dsRNA and cyantraniliprole co-delivery system: High-efficient control of two key pear pests while ensuring safety for natural enemy insects

Currently, the predominant method for managing pests in orchards is chemical control. However, prolonged use of chemicals leads to resistance issues and raise ecological safety. A promising approach to tackle these challenges involves nanoparticles-mediated delivery system of dsRNA and pesticides. Despite its potential, this strategy has not been widely applied in controlling pests in pear orchards. In this study, we developed a nanoparticle-mediated ternary biopesticide to tackle resistance and safety concerns associated with calmodulin dsRNA and cyantraniliprole. Initially, we assessed the effectiveness of cyantraniliprole against two key pear pests, Grapholita molesta and Cacopsylla chinensis. Subsequently, we observed an upregualtion of genes CaM and CN following cyantraniliprole treatment. Furthermore, inhibiting or silencing GmCaM and CcGaM enhanced the sensitivity to cyantraniliprole more effectively. By introducing hairpin RNA into the pET30a-BL21 RNaseIII- system to silence GmCaM and CcCaM, we developed a nanoparticle-mediated co-delivery system that exhibited improved control over these two pests. Importantly, our research demonstrated that using reduced cyantraniliprole dosages through ternary biopesticides could help mitigate risks to natural enemies. Overall, our research emphasizes the enhanced effectiveness of ternary biopesticides in boosting the performance of dsRNA and pesticide against pear pests, while fostering environmental sustainability-a novel advancement in this field.

A potential trade-off between reproduction and enhancement of thermotolerance in Liriomyza trifolii populations driven by thermal acclimation

The invasive pest, Liriomyza trifolii, poses a significant threat to ornamental and vegetable plants. It spreads rapidly and causes large-scale outbreaks with pronounced thermotolerance. In this study, we developed L. trifolii strains adapted to high temperatures (strains designated 35 and 40); these were generated from a susceptible strain (designated S) by long-term thermal acclimation to 35 °C and 40 °C, respectively. Age-stage, two-sex life tables, thermal preferences, critical thermal limits, knockdown behaviors, eclosion and survival rates as well as expression of genes encoding heat shock proteins (Hsps) were compared for the three strains. Our findings indicated that the thermotolerance of L. trifolii was enhanced after long-term thermal acclimation, which suggested an adaptive plastic response to thermal stress. A trade-off between reproduction and thermotolerance was observed under thermal stress, potentially improving survival of the population and fostering adaptionary changes. Acclimation at 35 °C improved reproductive performance and population density of L. trifolii, particularly by enhancing the fecundity of female adults and accelerating the speed of development. Although the 40 strain exhibited the highest developmental speed and greater thermotolerance, it incurred a larger reproductive cost. This study provides a theoretical framework for monitoring and controlling leafminers and understanding their evolutionary adaptation to environmental changes.

Cost-effectiveness evaluation of mass-rearing Cadra cautella (Lepidoptera: Pyralidae) based on harvest theory for sustainable alternative prey production

Cadra cautella (Walker) (Lepidoptera: Pyralidae) is a pest in barn, and its eggs are often utilized as an alternative prey or as hosts for mass production of insect predators and parasitoids. To aid in developing a mass-rearing system for C. castella, the suitability of using an artificial diet based on brown rice flour and whole brown rice was compared using the age-stage, 2-sex life table. Compared with those reared on brown rice, the insects reared on an artificial diet had a shorter preadult period (32.08 vs 37.38 d), higher fecundity (468.14 vs 356.20 eggs/female), greater intrinsic rate of increase (0.1509 vs 0.1145 d-1), and higher net reproductive rate (199.28 vs 103.52 offspring). Small populations were required to rear the moth on an artificial diet to achieve the same daily production of C. cautella. Still, the food expense was only 60.2% of that of C. cautella reared on brown rice. Approximately 99.44% of the eggs in each rearing procedure could be supplied as alternative prey for predators, with the remainder served to maintain the colonies for subsequent batches. Only eggs laid within 6 d would be utilized to ensure the high quality of alternative prey for the mass production of predacious bugs. Additionally, a multifunctional device was designed for moth rearing and egg collection, reducing labor input and minimizing health risks for workers coping with inhaled scales. To encourage the production of natural enemies, a cost-effective diet for maintaining a sustainable colony, and a system for daily egg-harvesting of alternative prey were proposed.

The sublethal concentration of acetamiprid suppresses the population growth of 2 species of wheat aphids, Sitobion miscanthi and Schizaphis graminum (Hemiptera: Aphididae)

Sitobion miscanthi and Schizaphis graminum (Rondani) are the 2 main aphid species that occur simultaneously, causing significant loss to wheat production. Acetamiprid has been used to control a variety of pests, including aphids. In this study, the sublethal effect of acetamiprid on S. miscanthi and S. graminum was evaluated using life-table analyses. The results showed that acetamiprid has a high toxicity to S. miscanthi and S. graminum with a LC50 of 1.90 and 3.58 mg/L at 24 h, respectively. The adult longevity and fecundity of S. miscanthi and S. graminum F0 generation were significantly reduced after being exposed to a sublethal concentration of acetamiprid. Additionally, the sublethal concentration of acetamiprid had negative transgenerational effects on S. miscanthi and S. graminum, which showed a significant decrease in fecundity and population life-table parameters involving age-stage-specific survival rate (sxj), age-specific survival rate (lx), and intrinsic rate of increase (r). Furthermore, the population projections showed that the total population size of S. miscanthi and S. graminum was significantly lower in the aphid group exposed to sublethal concentration of acetamiprid compared to the control group. These results suggest that sublethal concentration of acetamiprid suppresses the population growth of S. miscanthi and S. graminum. This finding is beneficial to the control of wheat aphids, and is important to fully understand the role of acetamiprid in integrated pest management.

Yellow Sticky Cards Reduce the Numbers of Trichogramma dendrolimi (Hymenoptera: Trichogrammatidae) Following Augmentative Releases against the Fruit Borers Carposina sasakii (Lepidoptera: Carposinidae) and Grapholita molesta (Lepidoptera: Tortricidae) in a Pear Orchard

Integrated pest management relies upon mutual compatibility among pest control tactics. The fruit-boring moths Carposina sasakii and Grapholita molesta can be devastating pests of pome and stone fruit production. Trichogramma dendrolimi parasitizes the eggs of these pests, preventing their eclosion, but its efficacy can be reduced by other pest control tactics. We tested T. dendrolimi attraction to five colors, and moth attraction to six colors, in laboratory choice tests, and thereafter deployed yellow sticky cards in tandem with releases of T. dendrolimi in field trials in a pear orchard. Yellow sticky cards deployed at high density trapped T. dendrolimi and reduced their numbers post-release. They also trapped adult G. molesta, which appeared to compensate for reduced egg parasitism on this species, but not on C. sasakii, which had higher abundance in plots with yellow sticky cards. The cards also captured adult lacewings, likely reducing their numbers in the field, but did not capture large numbers of lady beetles. The results suggest that yellow sticky cards can be used at high density to control aphids, psyllids and leafhoppers in early spring (March and April) when natural enemies are in low numbers, then removed in May so as not to interfere with augmentative releases of T. dendrolimi that must be timed to coincide with peak flights of fruit-boring moths. This strategy should enhance the compatibility of yellow sticky cards with egg parasitoid releases.

Compatibility of synthetic and biological pesticides with a biocontrol agent Phytoseiulus longipes (Acari: Phytoseiidae)

Phytoseiulus longipes is a predatory mite of Tetranychus evansi, which is an invasive pest in Africa and elsewhere. The introduction of this predator in Africa has considerable potential, but little is known about the compatibility of P. longipes with commonly used pesticides. Here, we examined lethal and sublethal effects of two pyrethroids (cypermethrin and deltamethrin), two organophosphates (dimethoate and chlorpyrifos), one nicotinoid (imidacloprid), two acaricides (propargite and abamectin), two naturally derived pesticides (oxymatrine and azadirachtin), and one entomopathogenic fungal-based formulation (Hirsutella thompsonii) on P. longipes eggs and adults. The pesticides were sprayed at their maximum recommended concentrations. Topical exposures to azadirachtin, imidacloprid, propargite, abamectin, oxymatrine, and H. thompsonii significantly reduced the net reproductive rate (R0), intrinsic rate of increase (r) and finite rate of increase (λ)of P. longipes. Pesticide lethal and sublethal effects on the predator were summarized in a reduction coefficient (Ex) for the classification based on IOBC toxicity categories. Results revealed that Azadirachtin and H. thompsonii were slightly harmful effects to adults. Imidacloprid, propargite, abamectin, and oxymatrine were moderately harmful to both eggs and adults. Residual persistence bioassays revealed that 4-day-old residue of azadirachtin had no harmful effect on the predator. Abamectin, oxymatrine, and H. thompsonii became harmless to it 10 days post-spraying, and propargite and imidacloprid were considered harmless after 20 days. Cypermethrin, deltamethrin, dimethoate, and chlorpyrifos were highly harmful to both eggs and adults, persistence remaining high even after 31 days of application. These findings provide valuable insights into decision-making when considering P. longipes for use in IPM programs.

Intergenerational Sublethal Effects of Flonicamid on Cotton Aphid, Aphis gossypii: An Age-Stage, Two-Sex Life Table Study

Flonicamid is a novel systemic insecticide widely used against aphids. However, the intergenerational sublethal effects of flonicamid on cotton aphid, Aphis gossypii, have not been fully studied. This study aimed to evaluate the sublethal effects of flonicamid on the biological parameters of adult A. gossypii (F0) and its subsequent intergenerational effects on the offspring (F1 generation) through age-stage, two-sex life table analysis. The results of the bioassays indicate that flonicamid exhibits significant toxicity toward adult A. gossypii, as evidenced by an LC50 value of 0.372 mg L-1 after a 48-h exposure period. The longevity, fecundity, and reproductive days of adult cotton aphids (F0) were significantly decreased when treated with the sublethal concentrations of flonicamid. The pre-adult stage exhibited an increase, whereas the adult longevity, total longevity, and fecundity experienced a notable decrease in F1 aphids after the exposure of F0 aphids to sublethal concentrations of flonicamid. Furthermore, the key demographic parameters, including r, λ, R0, and RPd, showed a significant decrease, while the total pre-reproductive period (TPRP) experienced a significant increase in the F1 generation. Collectively, our findings indicate that sublethal concentrations of flonicamid impact the demographic parameters of A. gossypii, resulting in suppression of population growth. This study presents comprehensive information on the overall impact of flonicamid on A. gossypii, which could potentially aid in managing this major pest.

The Food Source and Gut Bacteria Show Effects on the Invasion of Alien Pests-A Case of Bactrocera dorsalis (Hendel) (Diptera: Tephritidae)

How alien pests invade new areas has always been a hot topic in invasion biology. The spread of the Bactrocera dorsalis from southern to northern China involved changes in food sources. In this paper, in controlled conditions, we take Bactrocera dorsalis as an example to study how plant host transformation affects gut bacteria by feeding it its favorite host oranges in the south, its favorite host peaches and apples in the north, and feeding it cucumbers as a non-favorite host plant, thereby further affecting their fitness during invasion. The result showed that, after three generations of feeding on cucumbers, Bactrocera dorsalis took longer to develop as a larva while its longevity and fecundity decreased and pre-adult mortality increased. Feeding it cucumbers significantly reduced the overall diversity of gut microbiota of Bactrocera dorsalis. The relative abundance of Enterobacter necessary for survival decreased, while the Empedobacter and Enterococcus increased, resulting in decreased carbohydrate transport and metabolism and increased lipid transport and metabolism. Feeding Bactrocera dorsalis Empedobacter brevis and Enterococcus faecalis resulted in a 26% increase in pre-adult mortality and a 2-3 d increase in adult preoviposition period (APOP). Additionally, Enterococcus faecalis decreased the longevity of female and male adults by 17 and 12 d, respectively, and decreased fecundity by 11%. We inferred that the shifted plant hosts played an important role in posing serious harm to Bactrocera dorsalis invading from the south to the north. Therefore, after an invasion of Bactrocera dorsalis into northern China, it is difficult to colonize cucumbers for a long time, but there is still a risk of short-term harm. The findings of this study have established that the interactions between an insect's food source and gut bacteria may have an important effect on insect invasions.

Life Table Study of Liriomyza trifolii and Its Contribution to Thermotolerance: Responding to Long-Term Selection Pressure for Abamectin Resistance

Liriomyza trifolii is a significant invasive pest that targets horticultural and vegetable crops, causing large-scale outbreaks characterized by pronounced thermotolerance and insecticide resistance. This study examined the impact of long-term selection for abamectin resistance during the larval stage of L. trifolii on its population dynamics and thermal tolerance. We conducted a comprehensive comparison between the abamectin-resistant strain (AB-R) and the susceptible strain (S), including age-stage, two-sex life table analysis, thermal preference (Tpref), critical thermal maximum (CTmax), heat knockdown times (HKDTs), eclosion and survival rates, and LtHsp expression under heat stress. Our results showed that while selection for abamectin resistance was detrimental to survival and reproduction, it activated self-defense mechanisms and rapid adaptive adjustments and conferred modest thermal tolerance, which suggests a dual nature of insecticide effects. The AB-R strain exhibited significantly higher thermal preference and CTmax values, along with a longer HKDT and improved survival. Additionally, there was a significant upregulation of LtHsp expression in the AB-R strain compared to the S strain. These findings indicate that the evolution of thermal adaptation was accompanied by abamectin resistance development, emphasizing the necessity of considering temperature effects when applying chemical control. Our study provides valuable insights into how physiological acclimation may help mitigate the toxic effects of insecticides and illustrate how insects respond to multiple environmental pressures.

Utilizing Star Polycation Nanocarrier for the Delivery of miR-184 Agomir and Its Impact on the Life History Traits of the English Grain Aphid, Sitobion avenae

The investigation of genetics-based biopesticides has become a central focus in pesticide studies due to their inherent advantages, including species specificity, environmental safety, and a wide range of target genes. In this study, a mixture of miR-184 agomir and nanomaterial star polycation (SPc) was used to treat the nymphs of the English grain aphid, Sitobion avenae (F.). The life parameters of the aphids at various developmental stages were analyzed using an age-stage two-sex life table to assess the effect of miR-184 agomir on the experimental population. The results indicated that miR-184 agomir had a significant negative effect on four key life parameters, including the intrinsic rate of increase, the finite rate of increase, the net rate of increase, and the mean generation time. The population prediction revealed a substantial reduction (91.81% and 95.88%) in the population size of S. avenae at 60 d after treatment with miR-184 agomir, compared to the control groups. Our findings suggest that the miR-184 agomir has the potential to reduce the survival rate and mean longevity of S. avenae, highlighting its potential as a promising candidate for the development of an effective genetics-based biopesticide.

Demographic Parameters of Anthocoris minki Dohrn (Hemiptera: Anthocoridae) Reared on Common Bean (Phaseolus vulgaris L.), Faba Bean (Vicia faba L.) and Pea (Pisum sativum L.) as Egg Laying Media

Anthocoris minki Dohrn (Hemiptera: Anthocoridae) is used as a biological control agent of various agricultural pests. This study determined the effect of different egg laying materials, i.e., faba bean, common bean, and pea on population parameters of A. minki using age-stage, two-sex life table. The longest (34.45 d) and the shortest (21.32 d) adult longevity was noted on common bean and pea, respectively. Likewise, the highest (92%) and the lowest (69%) preadult survival rate was recorded on faba bean and pea, respectively. The highest fecundity (93.74 eggs/female) was noted on faba bean followed by common bean (43.95 eggs/female) and pea (48.69 eggs/female). Oviposition period remained unaffected, while higher oviposition days (22 d) were noted on faba bean compared with common bean (10 d) and pea (14 d). The shortest and the longest adult pre-oviposition period and total pre-ovipositional period were calculated for common bean and pea, respectively. The highest intrinsic rate of increase (r) (0.1159 d-1) and finite rate of increase (λ) (1.1229 d-1) were noted on common bean, while the lowest (r = 0.0939 d-1; λ = 1.0985 d-1) were noted on pea. Paired bootstrap analyses indicated that the highest net reproductive rate (R0) (43.12 offspring) was recorded on faba bean. Egg hatching rate significantly differed among plants (P < 0.01) and it was 80.50%, 71.10%, and 38.90% on common bean, faba bean and pea, respectively. It is concluded that faba bean would be the most suitable host for mass rearing of A. minki, while pea proved unsuitable.

Effects of miR-306 Perturbation on Life Parameters in the English Grain Aphid, Sitobion avenae (Homoptera: Aphididae)

MicroRNAs (miRNA) play a vital role in insects' growth and development and have significant potential value in pest control. Previously, we identified miR-306 from small RNA libraries within the English grain aphid, Sitobion avenae, a devasting insect pest for wheat. miR-306 not only involves in wing morphogenesis, but also is critically important for aphid survival. Its specific impacts on the life history traits, however, remain unclear. Here, we evaluate the impact of miR-306 perturbation on S. avenae populations using a two-sex life table approach. This comprehensive analysis revealed that miR-306 perturbation significantly prolongs the developmental stages (9.64% and 8.20%) and adult longevity of S. avenae, while decreasing pre-adult survival rate (41.45% and 38.74%) and slightly reducing average fecundity (5.80% and 13.05%). Overall, miR-306 perturbation negatively affects the life table parameters of the aphid population. The population prediction models show a significant decline in the aphid population 60 days post interference, compared to the control groups (98.14% and 97.76%). Our findings highlight the detrimental effects of miR-306 perturbation on S. avenae population growth and suggest potential candidate genes for the development of RNAi-based biopesticides targeted specifically at this pest species.

Hormetic effects of thiamethoxam on Schizaphis graminum: demographics and feeding behavior

In agroecosystems, insects contend with chemical insecticides often encountered at sublethal concentrations. Insects' exposure to these mild stresses may induce hormetic effects, which has consequences for managing insect pests. In this study, we used an electrical penetration graph (EPG) technique to investigate the feeding behavior and an age-stage, two-sex life table approach to estimate the sublethal effects of thiamethoxam on greenbug, Schizaphis graminum. The LC5 and LC10 of thiamethoxam significantly decreased longevity and fecundity of directly exposed adult aphids (F0). However, the adult longevity, fecundity, and reproductive days (RPd)-indicating the number of days in which the females produce offspring - in the progeny generation (F1) exhibited significant increase when parental aphids (F0) were treated with LC5 of the active ingredient. Subsequently, key demographic parameters such as intrinsic rate of increase (r) and net reproductive rate (R0) significantly increased at LC5 treatment. EPG recordings showed that total durations of non-probing (Np), intercellular stylet pathway (C), and salivary secretion into the sieve element (E1) were significantly increased, while mean duration of probing (Pr) and total duration of phloem sap ingestion and concurrent salivation (E2) were decreased in F0 adults exposed to LC5 and LC10. Interestingly, in the F1 generation, total duration of Np was significantly decreased while total duration of E2 was increased in LC5 treatment. Taken together, our results showed that an LC5 of thiamethoxam induces intergenerational hormetic effects on the demographic parameters and feeding behavior of F1 individuals of S. graminum. These findings have important implications on chemical control against S. graminum and highlight the need for a deeper understanding of the ecological consequences of such exposures within pest management strategies across the agricultural landscapes.

A Long Photoperiod Promoted the Development, Reproduction, and Predation of Harmonia axyridis Pallas (Coleoptera: Coccinellidae) at an Average Greenhouse Temperature during the Winter

To explore the feasibility of adjusting the photoperiod to regulate the life parameters and predation ability of Harmonia axyridis Pallas in greenhouses during the winter, life tables were constructed for H. axyridis under the three following photoperiods: 9L:15D (light/dark), 12L:12D, and 16L:8D at 15 °C, an average greenhouse temperature during the winter when aphids severely damage vegetables. The effects of photoperiods on predation by this ladybird were tested in both laboratory and greenhouse settings. The results showed that increased illumination promoted the development and reproduction of H. axyridis; under medium and long photoperiods, the pre-adult periods were 3.61 days and 4.34 days shorter than that under the short photoperiod, respectively, and the fecundity increased by 1.78 and 2.41 times. Population parameters r, λ, and R0 increased as illumination time increased, whereas T decreased. Increased illumination also increased the predation by third- and fourth-instar larvae and adults. The amounts of predation by fourth-instar larvae and adults increased by 22.16% and 75.09% under the medium photoperiod, and those under the long photoperiod increased by 71.96% and 89.64%, respectively. The numbers of Myzus persicae Sulzer predated by H. axyridis under the long photoperiod were higher than those under the short photoperiod in a greenhouse, and the predation parameters were influenced.

Thiamethoxam-Induced Intergenerational Sublethal Effects on the Life History and Feeding Behavior of Rhopalosiphum padi

Thiamethoxam, a second-generation neonicotinoid insecticide is widely used for controlling sap-sucking insect pests including Rhopalosiphum padi. The current study aimed to investigate the life-history parameters and feeding behavior of R. padi following treatments with sublethal concentrations of thiamethoxam. The lethal concentration 50 (LC50) value of thiamethoxam against adult R. padi was 11.458 mg L-1 after 48 h exposure. The sublethal concentrations of thiamethoxam (LC5 and LC10) significantly decreased the adult longevity, fecundity, and reproductive days in the directly exposed aphids (F0 generation). In the progeny R. padi (F1), the developmental durations and total prereproductive period (TPRP) were decreased while the adult longevity, fecundity, and reproductive days (RPd) were increased at both thiamethoxam concentrations. The demographic parameters including the net reproductive rate (R0), intrinsic rate of increase (r), and finite rate of increase (λ) were prolonged only at the LC5 of thiamethoxam. The EPG results indicated that the sublethal concentrations of thiamethoxam increases the total duration of non-probing (Np) while reducing the total duration of E2 in directly exposed aphids (F0). Interestingly, the E2 were significantly increased in the progeny generation (F1) descending from previously exposed parental aphids (F0). Overall, this study showed that thiamethoxam exhibited high toxicity against directly exposed individuals (F0), while inducing intergenerational hormetic effects on the progeny generation (F1) of R. padi. These findings provided crucial details about thiamethoxam-induced hormetic effects that might be useful in managing resurgences of this key pest.

Temperature-induced effects on development, reproduction, and predation of Harmonia axyridis fed on first instar larvae Spodoptera litura

Since metabolism, survival, and reproduction in hexapods are closely related to temperatures; changes in the mean and variance of temperature are major aspects of global climate change. In the typical context of biological control, understanding how predator-prey systems are impacted under thermal conditions can make pest control more effective and resilient. With this view, this study investigated temperature-mediated development and predation parameters of the predator Harmonia axyridis against the potential prey Spodoptera litura. The age-stage, two-sex life table of the predator was constructed at four temperatures (i.e. 15, 20, 25, and 30°C) by feeding on the first instar larvae of S. litura. Our results showed that the mean generation time (T) decreased but the intrinsic rate of increase (r) and the finite rate of increase (λ) increased with increased temperature. The mean duration of the total preadult stage decreased with higher temperatures. The T and r were 70.47 d and 0.0769 d-1 at 15°C; 58.41 d and 0.0958 d-1 at 20°C; 38.71 d and 0.1526 d-1 at 25°C; and 29.59 d and 0.1822 d-1 at 30°C, respectively. The highest net reproductive rate (R0) and fecundity were obtained at 25°C. The highest λ (1.1998 d-1) and lowest T (29.59 d) were obtained at 30°C, whereas the maximum net predation rate (C0) was at 25°C. Total population and predation rates projections were the highest at 30°C. Based on these findings, we anticipate that biological control strategies for this predator release against S. litura should be attuned to warming scenarios to achieve better biocontrol functions.

Trypanosoma cruzi infection reduces the population fitness of Mepraia spinolai, a Chagas disease vector

The hematophagous insect Mepraia spinolai (Hemiptera: Reduviidae: Triatominae) is naturally infected with the protozoan parasite Trypanosoma cruzi, the agent of Chagas disease in humans. In this study, we compared the demographic parameters of M. spinolai with and without T. cruzi infection. We collected the immature life table data of 479 M. spinolai individuals of control cohort (reared on mice without T. cruzi infection) and 563 M. spinolai individuals of treatment cohort (reared on mice with T. cruzi infection). Nymphs were maintained in individual compartments inside a growth chamber (26°C; 65-75%) until adult emergence; moulting and survival were recorded daily. For the adult life table study of the control, we used 24 pairs of adults from the control cohort. For the adult life table study of T. cruzi-infected cohort, 25 infected females were paired with 25 males from the control cohort. Life table data were analysed using bootstrap-match technique based on the age-stage, two-sex life table. The preadult survival rate (0.5282) of the control cohort was significantly higher than that of the infected cohort (0.2913). However, the mean fecundity of reproductive females (Fr  = 22.29 eggs/♀) and net reproductive rate of population (R0  = 5.07 offspring/individual) of the 0.5th percentile bootstrap-match control cohort were not significantly different from those of the infected cohort (Fr  = 23.35 eggs/♀, R0  = 3.77 offspring/individual). Due to the shorter total preoviposition period and higher proportion of reproductive female, the intrinsic rate of increase (r = 0.0053 d-1 ) and finite rate of increase (λ = 1.0053 d-1 ) of control cohort of M. spinolai were significantly higher than those of the T. cruzi-infected cohort (r = 0.0035 d-1 , λ = 1.0035 d-1 ). These results suggest that T. cruzi infection reduces the population fitness of the Chagas disease vector M. spinolai.

Life table parameters and digestive physiology of Aulacophora lewisii Baly (Coleoptera: Chrysomelidae) on three Luffa acutangula (L.) Roxb. (Cucurbitaceae) cultivars

Aulacophora lewisii Baly (Coleoptera: Chrysomelidae) is an important pest of Luffa acutangula (L.) Roxb. (Cucurbitaceae) in India. Larvae of A. lewisii feed on the roots, while adults consume leaves of L. acutangula. In the current study, effects of three L. acutangula cultivars (Abhiskar, Debsundari, and Jaipur Long) on the life table parameters by age-stage, two-sex approach, and key digestive enzymatic activities (amylolytic, proteolytic, and lipolytic) of the larvae and adults of A. lewisii were determined. Further, nutrients (total carbohydrates, proteins, lipids, amino acids, and nitrogen content) and antinutrients (total phenols, flavonols, and tannins) present in the roots and leaves of three cultivars were estimated. The development time (egg to adult emergence) was fastest and slowest on Jaipur Long (31.80 days) and Abhiskar (40.91 days), respectively. Fecundity was highest and lowest on Jaipur Long (279.91 eggs) and Abhiskar (137.18 eggs), respectively. The intrinsic rate of increase (r) was lowest on Abhiskar (0.0511 day-1) and highest on Jaipur Long (0.0872 day-1). The net reproductive rate (R0) was lowest on Abhiskar (23.32 offspring female-1). The mean generation time (T) was shortest on Jaipur Long (52.59 days) and longest on Abhiskar (61.58 days). The amylolytic, proteolytic, and lipolytic activities of larvae and adults of A. lewisii were highest and lowest on Jaipur Long and Abhiskar, respectively. The lower level of nutrients and higher level of antinutrients influenced higher larval development time and lower fecundity of A. lewisii on Abhiskar than other cultivars. Our results suggest that Abhiskar cultivar could be promoted for cultivation.

Control Effects of Short-Term Heatwaves on a Holocyclic Aphid

The soybean aphid, A. glycines, is an important soybean pest. Harbin, in the Heilongjiang Province, is an area with increasing temperatures in China that faces frequent short-term heatwaves. In this study, the development, reproduction, and morph differentiation of A. glycines have been studied when they were exposed to diurnal at 35 °C for seven days, beginning at different developmental stages. The nymph stage duration of A. glycines was longer, the adult lifespans and total lifespans were shorter, and their bodies were smaller when exposed to a diurnal of 35 °C beginning at the 1st to 4th stadium. The adult reproduction period was shorter, and the adult fecundity and intrinsic rate of increase were smaller than those of aphids reared at a diurnal of 25 °C. A higher and lower proportion of gynoparae and males were deposited as offspring on day 13 by adults when exposed to diurnal at 35 °C, beginning at the 1st to 4th stadium, respectively, than those of aphids reared at a constant of 20 °C. These results are important for predicting the dynamics of A. glycines in Harbin soybeans. This provides evidence that short-term heatwaves are probably useful for controlling A. glycines, by inhibiting development and male morphogenesis.

Parthenogenesis affects interspecific competition between Megalurothrips usitatus and Frankliniella intonsa (Thysanoptera: Thripidae) in changing environment: evidence from life table study

The thrips Megalurothrips usitatus Bagnall and Frankliniella intonsa Trybom (Thysanoptera: Thripidae) are important pests in cowpea-growing areas of south China. Parthenogenesis is an important reproductive form of thysanopterans, and plays an important role in maintaining population growth. To understand the developmental and reproductive characteristics of these 2 thrips species during parthenogenesis, we compared the age-stage life tables of M. usitatus and F. intonsa on cowpea pods under natural regimes during the summer and winter. The results showed that the total preadult period and total preoviposition period of M. usitatus were significantly longer than those of F. intonsa in both seasons. Moreover, longevity of adult M. usitatus (29.53 days) was shorter compared with adult F. intonsa (34.00 days) in summer, whereas higher fecundity (220.8 eggs/female) and more oviposition days (37.83 days) were observed in M. usitatus compared with F. intonsa in winter (fecundity = 179.83 eggs/female, oviposition days = 33.03 days). The net and gross reproductive rates of M. usitatus were significantly greater than those of F. intonsa during winter. In addition, the intrinsic and finite rates of increase of M. usitatus were significantly lower than those of F. intonsa, and the mean generation time of M. usitatus was significantly longer than that of F. intonsa both in summer and winter. These results indicated that parthenogenesis has species specificity among thrips, which in turn affects population development, especially under changing environments.

Effects of dimpropyridaz on feeding behavior, locomotivity and biological parameters of Aphis gossypii

Aphis gossypii is a worldwide agricultural pest insect that has developed resistance to multiple pesticides. Dimpropyridaz is a new chordotonal organ regulator and has been registered for control of sap-sucking insects including A. gossypii. For the aim to effectively apply dimpropyridaz for A. gossypii control, it is necessary to clarify the toxic effects of dimpropyridaz on cotton aphids. In the present study, the effects of dimpropyridaz on feeding behavior, locomotivity and biological parameters of A. gossypii were investigated. The bioassay results showed that dimpropyridaz had good insecticidal activity against A. gossypii, with LC50 as 1.91 mg/L at 72 h post exposure. Moreover, the dimpropyridaz treated A. gossypii showed obvious poisoning symptoms of dehydration and shrivel. Through the gentle-touch experiment and feeding experiment, it was found that dimpropyridaz treatment had significant adverse impacts on the locomotivity and feeding behavior of A. gossypii. Compared with the control group, the coordinated movement ability of the treated A. gossypii attenuated, moreover the feeding behavior of A. gossypii was inhibited. The feeding rate decreased by 62.00%, 64.00% and 71.67% after treatment with 50.33 mg/L dimpropyridaz for 24 h, 48 h and 72 h, respectively. Especially, EPG recordings showed that the number of intracellular stylet puncture and the total duration of phloem sap ingestion and concurrent salivation decreased substantially, while the total duration of non-probing increased after exposure to dimpropyridaz. Furthermore, the treatments with LC10 and LC30 of dimpropyridaz significantly reduced the longevity and fecundity of F0, and led to a decrease of the relative fitness of F0 to 0.48 and 0.32, respectively. The net reproductive rate (R0) and mean generation time (T) of F1 generation were also significantly reduced, moreover the duration of reproduction was significantly shortened. In addition, at 72 h post treatment with LC30 dimpropyridaz, the gene expression levels of JHEH and USP of cotton aphids significantly increased, while the expression of FOXO, INR, EcR and INRS decreased. These results provide basis for clarifying the toxicology of dimpropyridaz to cotton aphids, and also are beneficial for effective control of cotton aphid using dimpropyridaz.

miR-252 targeting temperature receptor CcTRPM to mediate the transition from summer-form to winter-form of Cacopsylla chinensis

Temperature determines the geographical distribution of organisms and affects the outbreak and damage of pests. Insects seasonal polyphenism is a successful strategy adopted by some species to adapt the changeable external environment. Cacopsylla chinensis (Yang & Li) showed two seasonal morphotypes, summer-form and winter-form, with significant differences in morphological characteristics. Low temperature is the key environmental factor to induce its transition from summer-form to winter-form. However, the detailed molecular mechanism remains unknown. Here, we firstly confirmed that low temperature of 10 °C induced the transition from summer-form to winter-form by affecting the cuticle thickness and chitin content. Subsequently, we demonstrated that CcTRPM functions as a temperature receptor to regulate this transition. In addition, miR-252 was identified to mediate the expression of CcTRPM to involve in this morphological transition. Finally, we found CcTre1 and CcCHS1, two rate-limiting enzymes of insect chitin biosyntheis, act as the critical down-stream signal of CcTRPM in mediating this behavioral transition. Taken together, our results revealed that a signal transduction cascade mediates the seasonal polyphenism in C. chinensis. These findings not only lay a solid foundation for fully clarifying the ecological adaptation mechanism of C. chinensis outbreak, but also broaden our understanding about insect polymorphism.

Effects of heat wave on development, reproduction, and morph differentiation of Aphis glycines (Hemiptera: Aphididae)

As global warming intensifies, heat waves occur frequently in the summer and autumn in Heilongjiang Province, northeast China. The soybean aphid, Aphis glycines Matsumura, is an important pest of soybean in the region, which faces great survival pressure due to high temperature. In this study, A. glycines fed soybean (AgFS) and wild soybean (AgFW) were exposed to diurnal 35 °C for 7 days begin at different developmental stages, and the development, reproduction, and morph differentiation were studied. When AgFS were exposed to heat waves from the second stadium to the adult stage, they performed worse in adult lifespan and fecundity than the control. When AgFW were exposed to heat waves begin at different developmental stages, the adult lifespan and reproduction period were shortened and reproduction ability decreased. When exposed to heat waves, the adult fecundity and intrinsic rate of increase in AgFW were lower than those of AgFS. Lower proportion of males were deposited on day 13, when AgFS and AgFW were exposed to diurnal 35 °C begin at different developmental stages. The results showed that heat waves lasting for 7 days were likely to be useful in the management of A. glycines, which reduced adult reproduction ability and male differentiation proportion in the offspring and significantly affected AgFW compared to AgFS. These results are important for predicting the dynamics of A. glycines in Heilongjiang, northeast China, where the local environmental temperature is increasing and heat waves occur frequently.

Effects of different host plants on the growth, development, and fecundity of Phthorimaea absoluta (Lepidoptera: Gelechiidae): an evaluation based on the age-stage two-sex life table

This study aimed to investigate the growth and development parameters of Phthorimaea absoluta (Meyrick) population at each stage when feeding on 4 host plants: Lycopersicon esculentum, Solanum tuberosum, Solanum melongena, and Nicotiana tabacum. The objective was to predict population dynamics and develop appropriate control strategies. The age-stage sex-life table was used to evaluate survival rate, fecundity, life expectancy, reproductive value, population parameters, and population growth prediction of P. absoluta after feeding on the 4 Solanaceae plants. The results showed significant variations in the fecundity parameters of P. absoluta among the different host plants. The L. esculentum population exhibited the highest average egg-laying period (13.17 ± 0.61 days) and average egg production (219.31 ± 21.02 eggs), while N. tabacum had the lowest values (4.56 ± 0.26 days and 26.08 ± 2.53 eggs, respectively). The gross reproduction rate of P. absoluta feeding on L. esculentum was 146.43 ± 21.00, which was 1.80, 3.77, and 6.39 times higher compared to S. tuberosum, S. melongena, and N. tabacum, respectively. The average age period and population doubling time of P. absoluta feeding on L. esculentum were lower than those of the other 3 host plants. These results indicated that while P. absoluta can complete a generation on L. esculentum, S. tuberosum, S. melongena, and N. tabacum, L. esculentum is the most suitable host for its growth and development. Therefore, in the occurrence and adjacent areas of P. absoluta, relevant authorities should promptly monitor and control its population in the planting areas of Solanaceae plants to prevent further spread.

Effects of cold storage after cold acclimation on the fitness of Habrobracon hebetor (Hymenoptera: Braconidae)

Habrobracon hebetor (Say) (Hymenoptera: Braconidae) is a cosmopolitan, idiobiont, and gregarious ectoparasitoid, which can parasitize the larvae of several pyralid and noctuid moths. However, adult parasitoids require cold storage to ensure that adequate individuals are available when a pest outbreak occurs. To understand the effects of cold storage after acclimation on offspring fitness of H. hebetor, the development, fecundity, population parameters, and paralysis rate of the F1 generation were evaluated using an age-stage, two-sex life table. Four pairing treatments were used in this study, with refrigerated males and females (ReF×ReM), unrefrigerated females and refrigerated males (UnF×ReM), refrigerated females and unrefrigerated males (ReF×UnM), and unrefrigerated females and males (UnF×UnM, control). Cold storage after acclimation had no significant effect on the fecundity or oviposition period of F0-generation H. hebetor. Moreover, the survival rate (Sa = 61.43%), proportion of females (Nf/N = 0.41), intrinsic rate of increase (r = 0.3450), finite rate of increase (λ = 1.4121), net reproduction rate (R0 = 149.47), and net paralysis rate (C0 = 74.52) of ReF×UnM and UnF×UnM (Sa = 50.00%, Nf/N = 0.34, r = 0.3297, λ = 1.3881, R0 = 155.69, C0 = 62.90, respectively) treatments were significantly higher than those of the ReF×ReM treatment (Sa = 45%, Nf/N = 0.16, r = 0.2277, λ = 1.2558, R0 = 68.81, C0 = 31.61, respectively) (except for the Sa of UnF×UnM treatment), and there was no significant difference between the 2 treatments. Overall, it is advisable to avoid simultaneous cold storage of female and male parasitoids or to add unrefrigerated males appropriately when using cold-stored parasitoids to control pests.

Laboratory-Induced Bifenthrin, Flonicamid, and Thiamethoxam Resistance and Fitness Costs in Rhopalosiphum padi

The bird cherry-oat aphid, Rhopalosiphum padi (L.) (Hemiptera: Aphididae) is one of the most economically important pests of wheat crops worldwide. Thiamethoxam, bifenthrin, and flonicamid are extensively used insecticides for controlling this key pest. However, the indiscriminate use of chemical insecticides has led to the development of resistance in insects. In this study, we assessed the development of selection-induced resistance to bifenthrin, flonicamid, and thiamethoxam under controlled laboratory conditions. Additionally, we employed the age-stage, two-sex life table method to examine the fitness of R. padi. After ten generations of selection, bifenthrin-, flonicamid-, and thiamethoxam-resistant strains of R. padi were developed with resistance levels of 34.46, 31.97, and 26.46-fold, respectively. The life table analysis revealed a significant decrease in adult longevity and fecundity in these resistant strains compared to susceptible strain. Furthermore, the key demographic parameters such as net reproductive rate (R0) and reproductive days exhibited a significant reduction in all resistant strains, while the intrinsic rate of increase (r) and finite rate of increase (λ) were decreased only in resistant strains to bifenthrin and thiamethoxam. Taken together, these findings provide a comprehensive understanding of laboratory-induced insecticide resistance evolution and the associated fitness costs in R. padi. This knowledge could help to design resistance management strategies against this particular pest of wheat.