Parasitic behavior and developmental morphology of Mesocomys trabalae (Hymenoptera: Eupelmidae), a promising parasitoid of the Japanese giant silkworm Caligula japonica (Lepidoptera: Saturniidae).

The egg parasitoid Mesocomys trabalae Yao, Yang, and Zhao is used as a biocontrol agent against the emerging defoliator pest Caligula japonica Moore in East Asia. It has been proven that the eggs of Antheraea pernyi Guérin-Méneville can be used as a factitious host for the mass production of M. trabalae. We examined the parasitic behavior and morphological characteristics of the developmental stages of M. trabalae reared on A. pernyi eggs. The parasitic behavior of M. trabalae encompasses 10 steps, involving searching, antennation, locating the oviposition site, drilling, probing, detecting, oviposition, host feeding, grooming, and resting, with the oviposition step further divided into 3 stages. We determined that the parasitoid released an egg during the second stage of the oviposition step, while her body remained in a relatively static state. Among all the steps in parasitic behavior, probing occupied the longest time, accounting for 26.33% of the entire parasitism process. It was followed by oviposition (15.88%), drilling (15.10%), antennation (13.09%), detecting (10.79%), host feeding (10.02%), and the remaining steps, each occupying less than 5.00% of the total time in steps. The pre-emergence of adult M. trabalae comprised of 4 stages: egg (0-1 day), larva (2-6 days), prepupa (7-11 days), pupa (12-20 days), followed by the development into an adult, and it usually took 20-22 days to develop from an egg into an adult at 25°C. This study advances our understanding of the biology of Mesocomys parasitoids and their mass-rearing for use in augmentation programs.

Neoseiulus mites as biological control agents against Megalurothrips usitatus (Thysanoptera: Thripidae) and Frankliniella intonsa (Thysanoptera: Thripidae) on cowpea crop: laboratory to field.

Megalurothrips usitatus (Bagnall) (Thysanoptera: Thripidae) and Frankliniella intonsa (Trybom) (Thysanoptera: Thripidae) have been detrimental to cowpea production in many countries. Laboratory experiments were conducted to determine the prey stage preference and functional response of 2 predatory mites species, Neoseiulus barkeri (Hughes) (Acari: Phytoseiidae), and Neoseiulus californicus (McGregor) (Acari: Phytoseiidae), towards 2 thrips species (TS), M. usitatus, and F. intonsa, at varying densities and life stages on cowpea. Results shown that Neoseiulus species had a preference for different life stages of prey. Neoseiulus barkeri consumed more M. usitatus nymphs, while N. californicus consumed more F. intonsa (second-instar nymphs). The functional response of the 2 Neoseiulus spp. to nymphs of 2 TS was Type II on cowpea. The higher attack rate coefficient (a') and shorter handling time (Th) values were found on N. barkeri against M. usitatus, and a similar trend was found for those in N. californicus against F. intonsa. Field-caged trials were conducted to evaluate the effectiveness of Neoseiulus spp. in controlling 2 TS. The results have shown that Neoseiulus spp. was effective in controlling the 2 TS, with varying control efficacies at high or low release rates. The study provided valuable information on using Neoseiulus spp. as biological control agents against M. usitatus and F. intonsa in cowpea crops.

Light intensity differentially mediates the life cycle of lepidopteran leaf feeders and stem borers.

BACKGROUND: Leaf feeders, such as Spodoptera frugiperda and Spodoptera litura, and stem borers Ostrinia furnacalis and Chilo suppressalis, occupy two different niches and are well adapted to their particular environments. Borer larvae burrow and inhabit the interior of stems, which are relatively dark. By contrast, the larvae of leaf feeders are exposed to sunlight during feeding. We therefore designed series of experiments to evaluate the effect of light intensity (0, 2000, and 10 000 lx) on these pests with different feeding modes. RESULTS: The development of all four pests was significantly delayed at 0 lx. Importantly, light intensity affected the development of both male and female larvae of borers, but only significantly affected male larvae of leaf feeders. Furthermore, the proportion of female offspring of leaf feeders increased with increasing light intensity (S. frugiperda: 33.89%, 42.26%, 57.41%; S. litura: 38.90%, 51.75%, 65.08%), but no significant differences were found in stem borers. This research also revealed that the survival rate of female leaf feeders did not vary across light intensities, but that of males decreased with increasing light intensity (S. frugiperda: 97.78%, 85.86%, 61.21%; S. litura: 95.83%, 73.54%, 58.99%). CONCLUSION: These results improve our understanding of how light intensity affects sex differences in important lepidopteran pests occupying different feeding niches and their ecological interactions with abiotic factors in agroecosystems. © 2024 Society of Chemical Industry.

Dual Effects of Cold Storage and Stored Host Eggs of Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae) on the Reproductive Capacity of Telenomus remus Nixon (Hymenoptera: Scelionidae).

Spodoptera frugiperda is the preferred host of the parasitoid Telenomus remus. Cold storage can preserve a sufficient quantity of parasitoids and their hosts in a laboratory colony for mass release. First, the effects of cold storage on the reproductive capacity of T. remus reared on non-stored S. frugiperda eggs and the hatching rate of unparasitized S. frugiperda eggs were investigated. Further, the dual effects of cold storage and stored S. frugiperda eggs on the reproductive capacity of T. remus were studied to determine the optimal storage conditions and the maximal shelf life for both the host and the parasitoid. The emergence rate, the number of adults produced, and the female proportion of T. remus were affected by cold storage factors. Pupae stored at 13 °C for 15 days is optimum for T. remus reared on non-stored S. frugiperda eggs. Spodoptera frugiperda eggs could only be stored at 10 °C for five days to be suitable for rearing T. remus. The optimum cold storage conditions for T. remus parasitizing stored eggs were 7 °C for 5 days in the larval stage. The maximal shelf lives of T. remus parasitizing cold-stored S. frugiperda eggs were 10 days. Cold storage affected the hatching rate of S. frugiperda eggs, thereby further affecting the reproductive capacity of T. remus. The findings suggest that different storage conditions should be used when mass-rearing T. remus on stored and non-stored eggs. Telenomus remus should be reproduced using fresh laid S. frugiperda eggs for maximum shelf life.

Ontogenetic morphological changes of the venom apparatus in 4 eupelmid egg parasitoids.

Parasitoid wasps, notably egg parasitoids of the family Eupelmidae (Hymenoptera: Chalcidoidea), a key natural enemy of insect pests, offer a sustainable approach to pest management in agriculture. This study investigated the venom apparatus's developmental dynamics across 4 species of eupelmid egg parasitoids: Anastatus. japonicus, Anastatus fulloi, Mesocomys trabalae and Mesocomys albitarsis. A comprehensive anatomical investigation revealed differences in the dimensions of the venom apparatus across different developmental stages in adult females. We found that the venom apparatus of these 4 studied species consists of a venom gland and a reservoir with an associated Dufour's gland. As the length of post-emergence increases, a significant enlargement in the venom apparatus is evident across all the studied parasitoid species. Notably, M. albitarsis consistently exhibites the shortest venom gland length, whereas that of A. fulloi is the longest among the observed species. At the high day age, the width of venom glands of the 2 Mesocomys species surpasses those of the Anastatus species; for the volume of the venom reservoir, there is a steady increase in all 4 species before the age of 6­7 days, with a decline on 8th day, especially for A. japonicus. This research provided new insights into the developmental trajectories of venom apparatus in eupelmid egg parasitoids and the potential impact of venom potency on their success.

Transgenerational hormesis and sublethal effects of five key insecticides for controlling Spodoptera frugiperda on its endoparasitoid Cotesia marginiventris.

BACKGROUND: The endoparasitoid Cotesia marginiventris (Cresson) is a promising biological control agent of the fall armyworm (FAW) Spodoptera frugiperda (Smith). Because the application of insecticides is one of the prime choices in pest management, we evaluated the sublethal and transgenerational effects of the five key insecticides-chlorantraniliprole, emamectin benzoate, spinetoram, Bacillus thuringiensis (Bt), and Mamestra brassicae nucleopolyhedrovirus (MbNPV)-on the parasitoid. RESULTS: Exposure to five insecticides at a concentration causing 10% mortality (LC10 ) caused hormetic effects in the parent generation (F0 ) by increasing the parasitism and reducing the immature duration. Interestingly, the hormetic response was also observed in the offspring generation indirectly exposed to the insecticides. Furthermore, insecticides increased the parasitism rate by 6.32-14.73% in the F1 generation, which was similar to that of the F0 generation (3.96-11.81%) compared with the control. No significant adverse effect was observed on the number of emerged parasitoids of the F1 and F2 generations. However, insecticides had a detrimental impact on body size and fecundity in the F1 and F2 generations, which showed a small body size with shorter hind tibiae and a significant reduction in the female ratio compared with the control; the exception was that chlorantraniliprole significantly improved the female ratio in the F2 generation. CONCLUSIONS: Five insecticides at LC10 induced transgenerational hormetic and sublethal effects on C. marginiventris. Our results provide a scientific basis for a better understanding of the long-term impacts of insecticides at sublethal doses on parasitoids, facilitating the development of improved integrated pest management programs for FAW control. © 2023 Society of Chemical Industry.

Comparative genomics reveals evolutionary drivers of the dietary shift in Hemiptera.

Hemiptera insects exhibit a close relationship to plants and demonstrate a diverse range of dietary preferences, encompassing phytophagy as the predominant feeding habit while a minority engages in carnivorous or haematophagous behaviour. To counteract the challenges posed by phytophagous insects, plants have developed an array of toxic compounds, causing significant evolutionary selection pressure on these insects. In this study, we employed a comparative genomics approach to analyse the expansion and contraction of gene families specific to phytophagous insect lineages, along with their adaptive evolutionary traits, utilising representative species from the Hemiptera order. Our investigation revealed substantial expansions of gene families within the phytophagous lineages, especially in the Pentatomomorpha branch represented by Oncopeltus fasciatus and Riptortus pedestris. Notably, these expansions of gene families encoding enzymes are potentially involved in hemipteran-plant interactions. Moreover, the adaptive evolutionary analysis of these lineages revealed a higher prevalence of adaptively evolved genes in the Pentatomomorpha branch. The observed branch-specific gene expansions and adaptive evolution likely contribute significantly to the diversification of species within Hemiptera. These results help enhance our understanding of the genomic characteristics of the evolution of different feeding habits in hemipteran insects.

Assessing the effectiveness of imidacloprid and thiamethoxam via root irrigation against Megalurothrips usitatus (Thysanoptera: Thripidae) and its residual effects on cowpea.

Systemic neonicotinoid insecticides (NEOs) applied by seed-treatment or root application have emerged as a prevalent strategy for early-season insect pest management. This research investigated the effectiveness of imidacloprid and thiamethoxam, administered through root irrigation, in managing thrips in cowpea [Vigna unguiculata (Linn.) Walp.], and the residual properties of both insecticides in cowpea and soil. The results show that thrips density depends on the application rate of insecticides. At the maximum application rate (1,500 µg/ml, active ingredient), imidacloprid and thiamethoxam controlled thrips densities below the economic injury level (EIL, the EIL of thrips on cowpea was 7/flower) for 20 days and 25 days with the density of 6.90 and 6.93/flower at the end of the periods, respectively. Imidacloprid and thiamethoxam residues decreased gradually over time and decreased sharply after 15 days after treatment (DAT), the 2 insecticides were not detected (<0.001 mg/kg) at 45 DAT. According to our findings, the application of imidacloprid and thiamethoxam via root irrigation proved residual control lasting up to 20-25 days for controlling thrips damage at experimental rates, with a strong association to their residual presence in cowpea (0.6223 < R2 < 0.9545). Considering the persistence of the imidacloprid and thiamethoxam, the maximum tested application rate (1,500 µg/ml) was recommended. As the residues of imidacloprid and thiamethoxam were undetectable in cowpea pods at all tested rates, it may be suggested that the use of each insecticide is safe for consumers and effective against thrips, and could be considered for integrated thrips management in the cowpea ecosystem.

Comparison of the biology of Frankliniella intonsa and Megalurothrips usitatus on cowpea pods under natural regimes through an age-stage, two-sex life table approach.

Two thrips, Megalurothrips usitatus (Bagnall) and Frankliniella intonsa (Trybom) are major pests of cowpea in South China. To realistically compare the growth, development and reproductive characteristics of these two thrips species, we compared their age-stage, two-sex life tables on cowpea pods under summer and winter natural environmental regimes. The results showed that the total preadult period of M. usitatus was 8.09 days, which was significantly longer than that of F. intonsa (7.06 days), while the adult female longevity of M. usitatus (21.14 days) was significantly shorter than that of F. intonsa (25.77 days). Significant differences were showed in male adult longevity (10.68 days for F. intonsa and 16.95 days for M. usitatus) and the female ratio of offspring (0.67 for F. intonsa and 0.51 for M. usitatus), and the total preadult period of M. usitatus (16.20 days) was significantly longer than that of F. intonsa (13.66 days) in the winter regime. The net reproductive rate (summer: R0 = 85.62, winter: R0 = 105.22), intrinsic rate of increase (summer: r = 0.3020 day-1, winter: r = 0.2115 day-1), finite rate of increase (summer: λ = 1.3526 day-1, winter: λ = 1.2356 day-1) and gross reproduction rate (summer: GRR = 139.34, winter: GRR = 159.88) of F. intonsa were higher than those of M. usitatus (summer: R0 = 82.91, r = 0.2741, λ = 1.3155, GRR = 135.71; winter: R0 = 80.62, r = 0.1672, λ = 1.1820, GRR = 131.26), and the mean generation times (summer: T = 14.73 days, winter: T = 22.01 days) of F. intonsa were significantly shorter than those of M. usitatus (summer: T = 16.11 days, winter: T = 26.25 days). These results may contribute to a better understanding of the bioecology of different thrips species, especially the interspecific competition between two economically important cowpea thrips with the same ecological niche in a changing environment.

Comparative Analysis of the Venom Proteins from Two Eupelmid Egg Parasitoids Anastatus japonicus and Mesocomys trabalae.

Parasitic wasps are abundant and diverse Hymenoptera insects that lay their eggs inside or on the external surface of the host and inject venom into the host to create a more favorable environment for the larvae to survive and regulate the host's immunity, metabolism, and development. But research on the composition of egg parasitoid venom is very limited. In this study, we used a combination of transcriptomic and proteomic approaches to identify the protein fractions of the venom in both eupelmid egg parasitoids, Anastatus japonicus and Mesocomys trabalae. We identified 3422 up-regulated venom gland genes (UVGs) in M. trabalae and 3709 in A. japonicus and analyzed their functions comparatively. By proteome sequencing, we identified 956 potential venom proteins in the venom pouch of M. trabalae, of which 186 were contained in UVGs simultaneously. A total of 766 proteins were detected in the venom of A. japonicus, of which 128 venom proteins were highly expressed in the venom glands. At the same time, the functional analysis of these identified venom proteins was carried out separately. We found the venom proteins in M. trabalae are well known but not in A. japonicus, which may be related to the host range. In conclusion, identifying venom proteins in both egg parasitoid species provides a database for studying the function of egg parasitoid venom and its parasitic mechanism.

Comparative demographics, population projections and egg maturation patterns of four eupelmid egg parasitoids on the factitious host Antherae pernyi.

BACKGROUND: The genera Anastatus and Mesocomys (both Hymenoptera: Eupelmidae) are important solitary egg endoparasitoids as biological control agents for lepidopterous and hemipterous pests worldwide. Here, we comparatively evaluated the demographic parameters of four important eupelmid egg parasitoids (Anastatus fulloi, A. japonicus, Mesocomys albitarsis and M. trabalae) reared on the factitious host eggs of the Chinese oak silkworm Antheraea pernyi, using age-stage two-sex life tables, their population projections as well as egg maturation patterns. RESULTS: Both the age-specific net reproductive rate (lx mx ) and reproductive value (vxj ) increased initially and then gradually decreased with increasing age in all four parasitoid species. Overall, the two Mesocomys species had higher survival rates at stable age-stage distribution, peak reproductive values, and intrinsic rates of increase than the two Anastatus species. Mesocomys albitarsis had the longest longevity, whereas A. japonicus had the longest oviposition days and mean generation time. The two Mesocomys species are thus projected to have faster population increase than the two Anastatus species. Adult females of all four parasitoid species emerged with only a few mature eggs (< 6 eggs) and most of their eggs were matured post-emergence (strict synovigeny). The estimated 90% of lifetime complement of reproduction (offspring) and realized days were 374 and 32 for A. japonicus, 337 and 22 for M. trabalae, 330 and 19 for M. albitarsis and 147 and 28 for A. fulloi. CONCLUSION: Our results indicated that the two Mesocomys species have higher control capacity than the two Anastatus species. Provision of adult food for these strictly synovigenic parasitoids would be essential to prolong their lifespan and continuously produce eggs for parasitizing their hosts for mass rearing or augmentative biological control programs. © 2023 Society of Chemical Industry.

Odorant-Binding Proteins and Chemosensory Proteins in Spodoptera frugiperda: From Genome-Wide Identification and Developmental Stage-Related Expression Analysis to the Perception of Host Plant Odors, Sex Pheromones, and Insecticides.

Spodoptera frugiperda is a worldwide generalist pest with remarkable adaptations to environments and stresses, including developmental stage-related behavioral and physiological adaptations, such as diverse feeding preferences, mate seeking, and pesticide resistance. Insects' odorant-binding proteins (OBPs) and chemosensory proteins (CSPs) are essential for the chemical recognition during behavioral responses or other physiological processes. The genome-wide identification and the gene expression patterns of all these identified OBPs and CSPs across developmental stage-related S. frugiperda have not been reported. Here, we screened for genome-wide SfruOBPs and SfruCSPs, and analyzed the gene expression patterns of SfruOBPs and SfruCSPs repertoires across all developmental stages and sexes. We found 33 OBPs and 22 CSPs in the S. frugiperda genome. The majority of the SfruOBP genes were most highly expressed in the adult male or female stages, while more SfruCSP genes were highly expressed in the larval or egg stages, indicating their function complementation. The gene expression patterns of SfruOBPs and SfruCSPs revealed strong correlations with their respective phylogenic trees, indicating a correlation between function and evolution. In addition, we analyzed the chemical-competitive binding of a widely expressed protein, SfruOBP31, to host plant odorants, sex pheromones, and insecticides. Further ligands binding assay revealed a broad functional related binding spectrum of SfruOBP31 to host plant odorants, sex pheromones, and insecticides, suggesting its potential function in food, mate seeking, and pesticide resistance. These results provide guidance for future research on the development of behavioral regulators of S. frugiperda or other environmentally friendly pest-control strategies.

Identification and Comparative Expression Profiles of Candidate Olfactory Receptors in the Transcriptomes of the Important Egg Parasitoid Wasp Anastatus japonicus Ashmead (Hymenoptera: Eupelmidae).

Anastatus japonicus Ashmead is an egg parasitoid wasp important for the biological control of fruit crop pests. The olfaction of parasitoids is crucial to searching for host pests in fruit crops. In this study, we sequenced and analyzed the antennal and abdominal transcriptomes of A. japonicus to better understand the olfactory mechanisms in this species. A total of 201 putative olfactory receptor genes were identified, including 184 odorant receptors (ORs) and 17 ionotropic receptors (IRs). Then, we assayed the tissue-specific and sex-biased expression profiles of those genes based on the transcriptional levels. In total, 165 ORs and 15 IRs had upregulated expression in the antennae. The expression levels of 133 ORs, including odorant receptor co-receptor (AjapORco), and 10 IRs, including AjapIR8a, were significantly different between the female and male antennae. Our results provide valuable information for further studies on the molecular mechanisms of the olfactory system in A. japonicus.

Identification of Chelonus sp. from Zambia and Its Performance on Different Aged Eggs of Spodoptera frugiperda.

The fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), is a migratory pest endemic, to tropical and subtropical regions of America. Biological control can effectively and sustainably control pests over a long period of time while reducing the frequency of pesticide use and ensuring the safety of agricultural produce. In our study, the egg-larval Chelonus species (Chelonus bifoveolatus) from parasitized eggs of Spodoptera frugiperda in Zambia were described and identified based on morphological and genetic characteristics. To evaluate the efficiency of C. bifoveolatus, their parasitism suitability on 0- to 2-day FAW eggs under laboratory conditions was compared. The results showed that C. bifoveolatus could accept all FAW eggs at 0-, 1- and 2-day-old age and complete development successfully. Significant differences were found among 0-, 1-, and 2-day-old host eggs with respect to egg-larva developmental duration of C. bifoveolatus, and the egg-larva developmental duration on 2-day-old eggs was significantly lower than those on 0- and 1-day-old eggs. No significant differences were observed in the parasitism, pupation, emergence, and female rates for C. bifoveolatus on various age eggs of FAW. Generally, the parasitism rate, pupal rate, and emergence rate at various ages of FAW eggs were higher than 90%, 75%, and 82%, respectively, and the longevity of female parasitoids was longer than male parasitoids, and the sex ratio of females to males was nearly 1:1. Our results indicate that C. bifoveolatus performed well on various ages of FAW eggs and is a potential biological control agent against FAW in Africa.

Cadmium contamination triggers negative bottom-up effects on the growth and reproduction of Frankliniella occidentalis (Thysanoptera: Thripidae) without disrupting the foraging behavior of its predator, Orius sauteri (Heteroptera: Anthocoridae).

Heavy metal contaminants may influence tri-trophic interactions among plants, herbivores, and their natural enemies and affect the results of pest management practices. We examined how the widely distributed heavy metal cadmium (Cd) could modify interactions between kidney bean, Phaseolus vulgaris L., western flower thrips, Frankliniella occidentalis Pergande, and a predator, Orius sauteri (Poppius) by examining Cd effects on the feeding damage on leaves, the growth and reproduction of the thrips, and the feeding and plant location selection behaviors of predators. Leaf feeding damage was significantly reduced only at the highest Cd treatment (625 mg L-1). Survival, reproduction, and population growth of thrips decreased with the increase of Cd treatment concentration (0, 25, and 625 mg L-1). The reproduction rate of thrips from the highest Cd treatment group was reduced to less than 30% of the controls. Predator choice of plants was not impacted at the lowest level of Cd treatment (25 mg L-1) when prey were excluded, but the predators were deterred from plants treated at the high level of Cd (625 mg L-1). However, the predators responded strongly to the presence of prey, and the Cd-based deterrence was effectively eliminated when prey were added. Thus, the presence of Cd can cause a bottom-up effect on the fitness of pests without disrupting the foraging behavior of its predator. Our results provide baseline data on the toxic impacts on the pest and predator, and indicate that the ecology of the system and the biological control efficiency would be potentially impacted by high levels of Cd (625 mg L-1).

Performance of Chouioia cunea reared from a coleopteran alternative host as a biocontrol agent against the invasive lepidopteran pest, Hyphantria cunea.

BACKGROUND: Chouioia cunea is a generalist pupal endoparasitoid. Native to Eurasia, the parasitoid has been mass-reared on an alternative lepidopteran host (Antheraea pernyi) to successfully control the exotic invasive lepidopteran pest Hyphantria cunea in China. To solicit more accessible hosts, this study evaluated the potential of an easily cultured coleopteran beetle (Tenebrio molitor) as a substitute for rearing C. cunea through comparing the relative performance of the parasitoids reared from both alternative hosts on H. cunea. RESULTS: Compared with those reared from A. pernyi, the parasitoids reared from T. molitor (i.e., T. molitor vs. A. pernyi groups) performed equally well in terms of parasitism rate (94.4 vs. 88.9%), number of offspring produced per parasitized host (278 vs. 286), and female body length (1.334 vs. 1.351 mm), hind-tibia length (0.322 vs. 0.324 mm) and number of mature oocytes in the ovarioles (171 vs. 187), or even better based on offspring pre-emergence time (16.0 vs 16.9 days) and percentages of emerged offspring (99.8 vs. 99.1%) and female offspring (97.1 vs. 91.3%). Flight performance testing indicated that young C. cunea adults emerged from T. molitor had a similar percentage of actively flying wasps (76.9 vs. 72.9%) and a lower percentage of inactive wasps (2.3 vs. 10.6%) when compared to those reared from A. pernyi. CONCLUSION: Given the remarkable adaptability of C. cunea and the vast availability of T. molitor as a common resource insect worldwide, this indigenous parasitoid could be mass-reared on T. molitor to improve the prospect of biological control of H. cunea in its invaded regions. © 2022 Society of Chemical Industry.

An odorant binding protein is involved in counteracting detection-avoidance and Toll-pathway innate immunity.

INTRODUCTION: Odorant-binding proteins (OBPs) are a class of small molecular weight soluble proteins that exist as expanded gene families in all insects, acting as ligand carriers mediating olfaction and other physiological processes. During fungal infection, a subset of insect OBPs were shown to be differentially expressed. OBJECTIVES: We tested whether the altered expression of insect OBPs during pathogenic infection plays a role in behavioral or immune interactions between insect hosts and their pathogens. METHODS: A wide range of techniques including RNAi-directed knockdown, heterologous protein expression, electrophysiological/behavioral analyses, transcriptomics, gut microbiome analyses, coupled with tandem mass spectrometry ion monitoring, were used to characterize the function of a locust OBP in host behavioral and immune responses. RESULTS: The entomopathogenic fungus Metarhizium anisopliae produces the volatile compound phenylethyl alcohol (PEA) that causes behavioral avoidance in locusts. This is mediated by the locust odorant binding protein 11 (LmOBP11). Expression of LmOBP11 is induced by M. anisopliae infection and PEA treatment. LmOBP11 participates in insect detection of the fungal-produced PEA and avoidance of PEA-contaminated food, but the upregulation of LmOBP11 upon M. anisopliae infection negatively affects the insect immune responses to ultimately benefit successful mycosis by the pathogen. RNAi knockdown of LmOBP11 increases the production of antimicrobial peptides and enhances locust resistance to M. anisopliae infection, while reducing host antennal electrophysiological responses to PEA and locust avoidance of PEA treated food. Also, transcriptomic and gut microbiome analyses reveal microbiome dysbiosis and changes in host genes involved in behavior and immunity. These results are consistent with the elevated expression of LmOBP11 leading to enhanced volatile detection and suppression of immune responses. CONCLUSION: These findings suggest a crosstalk between olfaction and immunity, indicating manipulation of host OBPs as a novel target exploited by fungal pathogens to alter immune activation and thus promote the successful infection of the host.

Parasitism and Suitability of Trichogramma chilonis on Large Eggs of Two Factitious Hosts: Samia cynthia ricini and Antheraea pernyi.

Trichogramma, an effective biological control agent, demonstrates promise in environmentally sustainable pest management through its parasitic action toward insect eggs. This study evaluates the parasitism fitness and ability of T. chilonis with regard to two factitious host eggs, aiming to develop a cost-effective biological control program. While T. chilonis demonstrated the ability to parasitize both host eggs, the results indicate a preference for ES eggs over COS eggs. The parasitism and emergence rates of T. chilonis regarding ES eggs (parasitism: 89.3%; emergence: 82.6%) surpassed those for COS eggs (parasitism: 74.7%; emergence: 68.8%), with a notable increase in the number of emergence holes observed in the ES eggs compared to the COS eggs. Moreover, the developmental time of T. chilonis for ES eggs (10.8 days) was shorter than that for COS eggs (12.5 days), resulting in a lower number of dead wasps produced. Notably, no significant difference was observed in the female ratios between the two species. A comprehensive analysis was conducted, comparing the size and shell thickness of the two factitious hosts. The ES eggs exhibited smaller dimensions (length: 1721.5 µm; width: 1178.9 µm) in comparison to the COS eggs (length: 2908.8 µm; width: 2574.4 µm), with the ES eggshells being thinner (33.8 µm) compared to the COS eggshells (47.3 µm). The different host species had an effect on the body length of the reared parasitoids, with T. chilonis reared on COS hosts exhibiting a larger body length (female: 626.9 µm; male: 556.7 µm) than those reared on ES hosts (female: 578.8 µm; male: 438.4 µm). Conclusively, the results indicate that ES eggs present a viable alternative to COS eggs for the mass production of Trichogramma species in biological control programs.

Flubendiamide Resistance and Its Mode of Inheritance in Tomato Pinworm Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae).

Tomato pinworm, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is the major pest of tomato crops in Pakistan. Insecticides are commonly used for the management of this insect-pest. To develop a better insecticide resistance management strategy and evaluate the risk of resistance evolution, a field collected population of the tomato pinworm was selected with flubendiamide in the laboratory. We investigated the genetics of flubendiamide resistance and concentration-mortality response to other insecticides by selecting a field strain of tomato pinworm with commercial flubendiamide formulation. Tuta absoluta was reciprocally crossed with resistant strain (Fluben-R) and was selected up to 13 generations, while F1 progeny was back-crossed with resistant parent (Fluben-R). The results of LC50 and Resistance Ratio (RR) demonstrated a higher resistance developed in field and laboratory-selected strains (G2 and G13, respectively). Field-collected and laboratory-selected (Fluben-R) strains demonstrated higher intensity of concentration-mortality response against chlorantraniliprole, thiamethoxam, permethrin, abamectin and tebufenozide compared to susceptible ones. Based on the overlapping of 95% FL, it demonstrated significant differences, revealing that it was not sex linked (autosomal) with no maternal effects. The backcross analysis of the F1´ resistant parent resulting in significant differences at all concentrations suggests that resistance is controlled by more than one factor; the null hypothesis was rejected and inheritance was under polygenic control. Resistance progression from 38 to 550 folds demonstrated that T. absoluta can develop a higher level of resistance to flubendiamide. Concentration-mortality response experiments demonstrated that the LC50 of some tested insecticides was higher for field-collected and laboratory-selected strains, suggesting that resistance mechanisms should be studied at a molecular level for better understanding. These results could be helpful to design resistance management strategies against the tomato pinworm.

Synergism of Adjuvants Mixed With Spinetoram for the Management of Bean Flower Thrips, Megalurothrips usitatus (Thysanoptera: Thripidae) in Cowpeas.

The bean flower thrips, Megalurothrips usitatus (Bagnall) is an economically important insect pest of cowpea, Vigna unguiculata (L.) Walp in south China. Spinetoram is a newly available commercial active ingredient in the spinosyn mode of action group of insecticides that has been recommended for thrips management in China. In this study, the toxicity and efficacy of spinetoram for controlling M. usitatus were evaluated and compared to six other conventional insecticides. In addition, the synergistic effects of adjuvants (Silwet 806, Silwet 618, AgroSpred 910, and AgroSpred Prime) mixed with spinetoram for thrips control on cowpea were evaluated in both the laboratory and the field. Results of this study showed that spinetoram had higher toxicity and field efficacy of M. usitatus than other tested insecticides. A significant increase in efficacy was observed when spinetoram was applied at a recommended rate of 0.67 ml/L, mixed with Silwets (806 and 618) at the rate of 0.5 ml/L. Reductions of 50% and 40% in thrips infestation in the field over treatments without adjuvants were observed 3- and 7-days posttreatments, respectively. However, no significant reduction of M. usitatus was recorded when spinetoram was mixed with AgroSpreds (910 and Prime). Furthermore, no significant differences were found in thrips infestation between spinetoram sprayed alone at the rate of 0.67 ml/L and a reduced rate of spinetoram (0.45 ml/L) mixed with Silwets (806 and 618). The current research shows that Silwets mixed with spinetoram has a synergistic effect in the management of thrips.