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Background: The complex interaction between plant viruses and their insect vectors is the basis for the epidemiology of plant viruses. The 'Vector Manipulation Hypothesis' (VMH) was proposed to demonstrate the evolution of strategies in plant viruses to enhance their transmission to new hosts through direct effects on insect vector behavior and/or physiology. However, the aphid vectors used in previous studies were mostly obtained by feeding on virus-infected plants and as a result, it was difficult to eliminate the confounding effects of infected host plants. Furthermore, the mechanisms of the direct effects of plant viruses on insect vectors have rarely been examined comprehensively., Results: We fed Sitobion avenae on an artificial diet infused with a purified suspension of Barley yellow dwarf virus (BYDV) PAV strain to obtain viruliferous aphids. We then examined their growth and reproduction performance, resistance to the parasitoid Aphidius gifuensis Ashmead, and feeding behavior. The results indicate that (1) viruliferous aphids had a shorter life span and a lower relative growth rate at the nymphal stage; (2) A. gifuensis had a lower parasitism rate, mummification rate, and emergence rate in viruliferous aphids; (3) Viruliferous aphids spent more time on non-probing and salivation behavior and had a shorter total duration of penetration and ingestion compared with healthy conspecifics., Conclusion: These results suggest that plant virus infection may directly alter vector fitness and behavior that improves plant virus transmission, but not vector growth. These findings highlight the mechanisms of VMH and the ecological significance of vector manipulation by plant viruses, and have implications for plant virus disease and vector management. © 2024 Society of Chemical Industry., (© 2024 Society of Chemical Industry.)

Heavy metal pollution threatens human and ecological health. Heavy metals can exist in the soil for a long time and migrate to organisms along the food chain. However, only a few studies have investigated the effects of a single stress on broad beans. Here, we aimed to characterize Cd and Pb bioaccumulation, at varying concentrations, in the broad bean, Vicia faba L. We also determined how the bioaccumulated metals are impacted by aphids that consume the plant. No significant difference was noted in the germination rates of broad beans at the early stage of planting (after 8 days), but eventually, the germination rates of broad beans at all time points first decreased and then increased, and the highest inhibition efficiency was observed in the T3 group (12.5 mg/L Cd 2+  + 50 mg/L Pb 2+ ). Fourteen days after planting, there was no significant difference in seedling height between the T5 (50 mg/L Cd 2+  + 200 mg/L Pb 2+ ) and control groups; however, that in the other groups decreased significantly and there was no dependence between stress concentration and inhibition efficiency. In addition, both Cd and Pb in the soil could be transferred to broad beans, and the concentration of Pb in the roots of broad beans was greater than that of Cd, whereas the opposite was observed in the stems and leaves. Notably, under mixed stress, aphids could significantly reduce the content of Cd in broad beans; similarly, the Pb content in the roots and stems of broad beans decreased significantly after being infested with aphids but increased significantly in the leaves. Further, the aphid infestation decreased the Pb content in the soil and the soil Cd content in the highest concentration group (T5 group) (50 mg/L Cd 2+  + 200 mg/L Pb 2+ ). These results highlight the necessity of focusing on the effect of insects on heavy metal remediation in plants and provide a new perspective for reducing plant Cd toxicity., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

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 LC 5 and LC 10 of thiamethoxam significantly decreased longevity and fecundity of directly exposed adult aphids (F 0 ). However, the adult longevity, fecundity, and reproductive days (RP d )-indicating the number of days in which the females produce offspring - in the progeny generation (F 1 ) exhibited significant increase when parental aphids (F 0 ) were treated with LC 5 of the active ingredient. Subsequently, key demographic parameters such as intrinsic rate of increase (r) and net reproductive rate (R 0 ) significantly increased at LC 5 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 F 0 adults exposed to LC 5 and LC 10 . Interestingly, in the F 1 generation, total duration of Np was significantly decreased while total duration of E2 was increased in LC 5 treatment. Taken together, our results showed that an LC5 of thiamethoxam induces intergenerational hormetic effects on the demographic parameters and feeding behavior of F 1 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., (© 2024. The Author(s).)

Background: Harmonia axyridis is an effective natural enemy insect to a variety of phloem-sucking pests and Lepidopteran larvae, such as aphids, scabies, and phylloxera, while its industrial production is limited due to unmature artificial diet. Insect intestinal microbiota affect host development and reproduction. The aim of this study is to understand intestinal microbiota composition of H. axyridis and screen effective probiotics on artificial diet. Considering the role of the components and composition of the diet on the structure and composition of the intestinal microbiome, four kinds of diets were set up: (1) aphid; (2) basic diet; (3) basic diet + glucose; (4) basic diet + trehalose. The gut microbiota of H. axyridis was detected after feeding on different diets., Results: Results showed that the gut microbiota between artificial diet group and aphid groups were far apart, while the basic and glucose groups were clearly clustered. Besides, the glucose group and trehalose group had one unique phylum, Cryptophyta and Candidatus Saccharibacteria, respectively. The highest abundance of Proteobacteria was found in the aphid diet. The highest abundance of Firmicutes was found in the basic diet. However, the addition of glucose or trehalose alleviated the change. In addition, the relative abundance of Enterobacter, Klebsiella, Enterobacteriaceae_unclassified, Enterobacteriales_unclassified and Serratia in the aphid group was higher than other groups. Moreover, the function of gut genes in each group also showed clear differences., Conclusion: These results have offered a strong link between artificial diets and gut microbes, and also have provided a theoretical basis for the screening of synergistic probiotics in artificial diet., (© 2023. The Author(s).)

Flonicamid is a novel systemic insecticide that efficiently controls sap-sucking insect pests. However, the impact of sublethal concentrations of flonicamid on key demographic parameters and the feeding behavior of greenbug, Schizaphis graminum has not yet been studied. In this study, we used the age stage, two-sex life table approach, and electrical penetration graphs (EPGs) to investigate the sublethal effects of flonicamid on the biological traits and feeding behavior of S. graminum. Bioassays showed that flonicamid possesses high toxicity to adult S. graminum with LC 50 of 5.111 mg L -1 following 48 h exposure. Sublethal concentrations of flonicamid (LC 5 and LC 10 ) significantly decreased the longevity and fecundity of directly exposed parental aphids (F 0 ), while the reproductive days were reduced only at LC 10 . The pre-adult stage and total pre-reproductive period (TPRP) increased in F 1 individuals after exposure of F 0 aphids to the sublethal concentrations of flonicamid. Furthermore, the adult longevity, fecundity and key demographic parameters (R 0 , r, and λ) were significantly reduced in progeny generation (F 1 ). EPG recordings showed that the total duration of phloem sap ingestion and concurrent salivation (E2) decreased substantially in F 0 and F 1 aphids after exposure to LC 5 and LC 10 of flonicamid. Taken together, our results showed that the sublethal concentrations of flonicamid affect the demographic parameters and feeding behavior that ultimately suppress the population growth of S. graminum. This study provides in-depth information about the overall effects of flonicamid on S. graminum that might help to manage this key pest., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Background: Repellent plants (RPs), generally used to keep pests away from crops in integrated pest management, have been shown to reduce the need for synthetic insecticide sprays in various agroecosystems. However, few studies have evaluated the pest control efficiency of RPs over the entire growth period of crops. To evaluate the effect of RPs against Myzus persicae and explore the application and management modes of RPs in the field, we planted mint (Mentha haplocalyx), mung bean (Vigna radiata), celery (Apium graveolens) and coriander (Coriandrum sativum) near the ventilation openings of commercial greenhouses., Results: Five-month sampling results showed that mung bean and mint treatments significantly reduced M. persicae population levels over the entire growth period, whereas celery and coriander reduced aphid infestations during the main harvest period of eggplant. The four RP species showed the strongest repellence during their fast-growth periods. Mung bean and mint shortened the activity period of M. persicae in pepper by delaying the pest in reaching its peak activity. Celery and coriander reduced aphid density on eggplant during their main activity period. Mint, celery and coriander inhibited population growth in M. persicae in the laboratory, revealing the potential value of RPs in reducing M. persicae population levels in the field., Conclusion: Mint, mung bean, celery and coriander planted near ventilation openings could be used to control M. persicae infestations in commercial greenhouses. Early planting and timely replanting of RPs is a more effective, environmentally friendly and suitable method for organic pest control compared with chemical pesticides. © 2021 Society of Chemical Industry., (© 2021 Society of Chemical Industry.)

Background: The on-farm deployment of genetically modified crops may negatively affect nontarget arthropods, potentially disrupting food web structure and ecosystem functions. Aphid-parasitoid interactions are well-suited to study these potential impacts in agro-ecosystems. Over the span of 8 years, we systematically compared infestation levels of the aphid Aphis gossypii, its associated parasitoid community and overall parasitism rate between transgenic Cry1Ac + CpTI cotton and nontransgenic cotton. Furthermore, we measured the impact of transgenic Cry1Ac + CpTI cotton on structural traits and interspecies interactions within quantitative aphid-parasitoid food webs., Results: Transgenic Cry1Ac + CpTI cotton did not affect the abundance of aphids and parasitoids, or in-field parasitism rates. Despite weak interannual variability, transgenic Cry1Ac + CpTI cotton also did not alter food web architecture or biological control services., Conclusions: Our work not only elucidates the impact of transgenic Cry1Ac + CpTI cotton on different nontarget arthropods (i.e. aphids, parasitoids, hyperparasitoids) and their associated ecosystem services or disservices, but also diversifies the ecological risk assessment toolbox for transgenic insecticidal crops. © 2021 Society of Chemical Industry., (© 2021 Society of Chemical Industry.)

The pea aphid Acyrthosiphon pisum hosts different facultative symbionts (FS) which provide it with various benefits, such as tolerance to heat or protection against natural enemies (e.g., fungi, parasitoid wasps). Here, we investigated whether and how the presence of certain FS could affect phenoloxidase (PO) activity, a key component of insect innate immunity, under normal and stressed conditions. For this, we used clones of A. pisum of different genetic backgrounds (LL01, YR2 and T3-8V1) lacking FS or harboring one or two (Regiella insecticola, Hamiltonella defensa, Serratia symbiotica + Rickettsiella viridis). Gene expression and proteomics analyses of the aphid hemolymph indicated that the two A. pisum POs, PPO1 and PPO2, are expressed and translated into proteins. The level of PPO genes expression as well as the amount of PPO proteins and phenoloxidase activity in the hemolymph depended on both the aphid genotype and FS species. In particular, H. defensa and R. insecticola, but not S. symbiotica + R. viridis, caused a sharp decrease in PO activity by interfering with both transcription and translation. The microinjection of different types of stressors (yeast, Escherichia coli, latex beads) in the YR2 lines hosting different symbionts affected the survival rate of aphids and, in most cases, also decreased the expression of PPO genes after 24 h. The amount and activity of PPO proteins varied according to the type of FS and stressor, without clear corresponding changes in gene expression. These data demonstrate that the presence of certain FS influences an important component of pea aphid immunity., (© 2020 Institute of Zoology, Chinese Academy of Sciences.)

Nitrogen (N) and water are crucial in crop production but increasingly scarce environmental resources. Reducing their inputs can affect the whole plant-arthropod community including biocontrol agents. In a multitrophic system, we studied the interaction of the bottom-up effects of moderately reduced N concentration and/or water supply as well as the top-down effects of pests of different feeding guilds on plant nutritional quality (N and carbon concentration), direct defense (alkaloids and phenolics), and indirect defense (plant volatile organic compounds); on herbivore performance and host quality (N and carbon) to parasitoids and the latter's performance. Studied organisms were tomato plants, the sap feeders Macrosiphum euphorbiae and Bemisia tabaci, the leaf chewers Tuta absoluta and Spodoptera littoralis, and the parasitic wasps Aphelinus abdominalis and Necremnus tutae. Resource limitation affected plant quality, triggering bottom-up effects on herbivore and parasitoid performance, except for T. absoluta and N. tutae. Feeding guild had a major influence: bottom-up effects were stronger on sap feeders; N effects were stronger on sap feeders while water effects were stronger with leaf chewers (S. littoralis). Top-down effects of leaf chewer herbivory partly attenuated bottom-up effects and partly suppressed plant defenses. Bottom-up effects weakened when cascading up trophic levels. In summary, the interaction between plants, pests, and beneficial insects was modulated by abiotic factors, affecting insect performance. Simultaneous abiotic and biotic impact shaped plant biochemistry depending on the feeding guild: the biotic top-down effect of leaf chewer herbivory attenuated the bottom-up effects of plant nutrition and hence dominated the plant biochemical profile whereas in sap feeder infested leaves, it corresponded to the abiotic impact. This study highlights the plant's finely tuned regulatory system facilitating response prioritization. It offers perspectives on how smart manipulation of plant nutrient solutions might save resources while maintaining efficient biocontrol in crop production., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Nanotechnology is a new field in the pesticide industry. Nanopesticides represent an emerging technological tool that offers a range of benefits including increased efficacy, durability, and reduction in the amounts of used active ingredients. However, due to the lack of studies on the toxicity and the sublethal effects on pests and natural enemies, the extent of action and fate of these nanopesticdes is still not fully understood limitting thus their wide use. In this study, we encapsulated the pirimicarb insecticide using nanostructured lipid carriers (NLC) and investigated the toxicity and sublethal effects (LC 25 ) of the resulting nanocapsules against the cabbage aphid, Brevicoryne brassicae (Linnaeus) (Hemiptera: Aphididae) and its natural enemy the green lacewings Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae). Nanoencapsulation of pirimicarb enhanced 12.6-fold its toxicity to cabbage aphids compared to its commercial formulation. Furthermore, analysis of the age-stage, two-sex life table showed that negative effects on the B. brassicae aphid population growth were observed on F0 and F1 generations when aphids of parental (F0) generation were exposed to subelethal dose (LC 25 ) of both formulations of pirimicarb. However, negative effects from sublethal exposure to the commercial and nanoformulated pirimicarb resulted in significant reduction on the net reproductive rate, intrinsic rate of natural increase, and finite rate of increase of the green lacewings C. carnea. Our findings indicate that the approaches and assumptions used to assess the risks of conventional insecticides may not apply for nanopesticides. Further research is still needed to better understand the environmental impact of these compounds.

The melon aphid, Aphis gossypii is a globally distributed crop pest with a wide host range. The intensive use of insecticides against this insect over several years has led to develop resistance against many insecticides including acetamiprid. Understanding the relationship between acetamiprid resistance and fitness of A. gossypii is essential to limit the spread of the resistant population in the field. In this study, age-stage, two-sex life table approach was used to investigate these relationships in the lab. Results showed that resistant strain (Ace-R) had a reduced fitness (relative fitness = 0.909) along with significantly decreased adult longevity, fecundity, net reproductive (R 0 ), mean generation time (T) and gross reproductive rate (GRR). Compared to the susceptible strain (Ace-S), the pre-adult period and total pre-oviposition period (TPOP) were also significantly shorter in Ace-R strain. Moreover, the expression profiles of EcR, JHBP, JHAMT, JHEH, USP and Vg genes supposed to be involved in insect reproduction and development were analyzed using Quantitative Real Time PCR. The EcR, JHBP, JHAMT and USP genes were up-regulated, Vg gene was down-regulated while the mRNA level of JHEH gene was statistically same in the Ace-R strain compared to the Ace-S strain. Collectively, this study provides the occurrence and magnitude of fitness costs of A. gossypii against acetamiprid resistance and could be helpful to manage the resistance evolution in field populations., (Copyright © 2020 Elsevier Inc. All rights reserved.)

In agroecosystems, plant-pest interactions are at the basis of complex food webs, which can be affected by both biotic and abiotic factors. In the present study, we evaluated the impact of the insecticide beta-cypermethrin on interspecific interactions between the specialist aphid Aphis glycines and the generalist aphid Aulacorthum solani on soybean. Aphis glycines showed higher fecundity than A. solani on soybean and the aphids caused unbalanced reduction in population growth on each other. A sublethal concentration of beta-cypermethrin (LC 5 for A. glycines) stimulated the reproduction of A. glycines but it did not impact the fecundity of A. solani. However, the LC 5 of beta-cypermethrin enhanced the interspecific inhibition of fecundity between the two aphid species. Moreover, the two species showed different spatial distribution on soybean seedlings. Aphis glycines mainly aggregated on the stem of soybean plant while A. solani colonized soybean leaves. The LC 5 of beta-cypermethrin drove A. solani migrating from soybean leaves to stems independently of interspecific competition. Aphis glycines facilitated A. solani colonization on soybean plant through impacting host susceptibility, and vice versa. Nevertheless, such facilitated colonization-induced susceptibility could be modulated through exposure to the LC 5 of beta-cypermethrin. These findings hinted that the pyrethroid insecticide beta-cypermethrin has the potential to mediate the interspecific competition between specialist and generalist aphids (at the sublethal concentration of LC 5 ), and that it could influence aphid population growth and community structure in soybean crops. This knowledge could contribute to rationalize application of insecticides and to optimize Integrated Pest Management in soybean., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Cytochrome P450 monooxygenases (P450s) are highly conserved multifunctional enzymes that play crucial roles in insecticide resistance development. In this study, the molecular mechanisms of P450s in acetamiprid resistance development to melon aphid, Aphis gossypii was investigated. Acetamiprid resistant (32.64-fold resistance) population (Ace-R) of A. gossypii was established by continuous selection with acetamiprid for 24 generations. Quantitative Real Time PCR was carried out to analyze the expression of P450 genes in both acetamiprid resistant (Ace-R) and susceptible (Ace-S) strains. Result showed that nine genes (CYP6CY14, CYP6DC1, CYP6CZ1, CYP6DD1, CYP6CY5, CYP6CY9, CYP6DA1, CYP6CY18, and CYP6CY16) of CYP3 clade, four genes (CYP302A1, CYP315A1, CYP301A1, and CYP314A1) of CYP2 clade, two genes (CYP4CK1, CYP4G51) of CYP4 clade and three genes (CYP306A1, CYP305E1, CYP307A1) of mitochondrial clade (Mito clad) were significantly up-regulated, in Ace-R compared to Ace-S strain. Whilst CYP4CJ2 gene from (CYP4 clade) was significantly down-regulated in Ace-R strain. Furthermore, RNA interference-mediated knockdown of CYP6CY14, CYP6DC1, and CYP6CZ1 genes significantly increased the sensitivity of Ace-R strain to acetamiprid. Taken together, this study showed that P450 genes especially CYP6CY14, CYP6DC1 and CYP6CZ1 are potentially involved in acetamiprid resistance development in A. gossypii. This study could be useful to understand the molecular basis of acetamiprid resistance mechanism in A. gossypii., Competing Interests: Declaration of Competing Interest The authors declare that they have no conflicts of interest with the contents of this article., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Systemic neurotoxic insecticides are widely used to control aphid pests worldwide and their potential non-target effects on aphid predators are often unknown. Behavioral responses linked to biological control services are crucial when assessing the compatibility of chemicals with biocontrol organisms. This is particularly relevant for insecticides at low and sublethal concentrations. We studied the acute toxicity and the sublethal effect on the voracity of the generalist predator Harmonia axyridis (Coleoptera: Coccinellidae) caused by the exposure to three systemic insecticides routinely used against aphids. The tested insecticide concentrations were the Lethal Concentration 50% (LC 50 ), 20% (LC 20 ) and 1% (LC 1 ) estimated for the target pest Aphis gossypii (Hemiptera: Aphididae) in a companion study. The survival and the voracity differed among the tested chemicals and concentrations, but only thiamethoxam at LC 50 caused a significant predator mortality, and individuals that survived showed a reduced predation rate. The predators showed a density independent functional response after the exposure to most of the insecticide-concentration combinations, while an inverse density dependence of the prey consumption rate was observed for coccinellids exposed to sulfoxaflor and thiamethoxam at their lowest tested concentration. The estimated parameters, i.e., the attack rate and the prey handling time, were affected at higher concentrations by both imidacloprid and sulfoxaflor. These findings stress the importance of carefully evaluating side effects of insecticides at very low concentrations on beneficial arthropods in the risk assessment schemes for sustainable pest control programmes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Clothianidin is a second-generation neonicotinoid insecticide, widely used against sap-sucking insect pest including melon aphid, Aphis gossypii Glover (Hemiptera: Aphididae). This pest causes severe economic damage to Cucurbitaceae plants worldwide. In this study, we investigated clothianidin resistance development under continuous selection pressure. Moreover, the age-stage, two-sex life table approach was used to evaluate the impact of clothianidin resistance on the fitness of A. gossypii. A clothianidin resistant strain (CT-R) with a 23.17-fold resistance level was developed from a susceptible strain (CT-S) after continuous selection for 24 generations. Life table results showed a significant reduction in the relative fitness (0.847) of CT-R strain compared to the CT-S strain of A. gossypii. The developmental duration, oviposition days, total pre-oviposition period (TPOP), longevity, and fecundity of CT-R strain were found to be significantly lower when compared to CT-S strain. The demographic parameters, including the intrinsic rate of increase (r), finite rate of increase (λ), net reproductive rate (R0), and mean generation time (T) were also significantly decreased in CT-R strain compared to the CT-S strain. Both the reproductive and survival rates were affected by clothianidin resistance in CT-R strain compared with the CT-S strain of A. gossypii. Overall, our results demonstrate that in-depth knowledge about the trade-off at play between resistance degree and fitness cost might be useful to design resistance management strategies against A. gossypii., Competing Interests: The authors have declared that no competing interests exist.

Systemic insecticides are used to control agricultural pests globally and their non-target impact at non-lethal doses on beneficial arthropods has been recognized. We assessed the baseline toxicity of imidacloprid, thiamethoxam and sulfoxaflor-based insecticides on the polyphagous aphid pest, Aphis gossypii (Hemiptera: Aphididae), and their non-target effects on its main parasitoid, Aphidius colemani (Hymenoptera: Braconidae), evaluated by residual contact exposure to the median lethal (LC 50 ), the low lethal (LC 20 ) and the sublethal (LC 1 ) concentrations of the three tested insecticides, earlier estimated for the target pest. The results showed that the LC 50 s for the aphid were 6.4 × 10 -3 , 5 × 10 -3 , 2.9 × 10 -2 times lower compared to the label concentrations of imidacloprid, thiamethoxam and sulfoxaflor, respectively. LC 50 of thiamethoxam caused the highest mortality rate on the parasitoid followed by sulfoxaflor, while imidacloprid had the lowest impact. No significant sublethal effects on reprodution were observed for A. colemani survived to the insecticide exposure. Our findings highlight the importance of case-specific evaluation to optimize pesticide applications in Integrated Pest Management packages taking into account the ecological services provided by biological control agents., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Insecticide induced-hormesis, a bi-phasic phenomenon characterized by low dose stimulation and high dose inhibition following exposure to insecticide, is crucial to insect pest resurgence. In this study, the effects of low or sublethal concentrations of thiamethoxam on biological traits and genes expression were investigated for Aphis gossypii Glover following 72 h exposures. Leaf-Dip bioassay results showed that thiamethoxam was very toxic against adult A. gossypii with an LC 50 of 1.175 mg L -1 . The low lethal (LC 15 ) and sublethal (LC 5 ) concentrations of thiamethoxam significantly reduced longevity and fecundity of the directly exposed aphids. However, stimulatory effects on pre-adult stage, longevity, and fertility were observed in the progeny generation (F 1 ) of A. gossypii, when parental aphids (F 0 ) were exposed to LC 15 of thiamethoxam. Subsequently, biological traits such as intrinsic rate of increase (r), finite rate of increase (λ), and net reproductive rate (R 0 ) increased significantly to F 1 individuals due to LC 15 treatment. No significant responses were observed for LC 5 of thiamethoxam. The LC 15 of thiamethoxam significantly increased the expression level of vitellogenin and ecdysone receptors genes in progeny generation, while no effects were observed for treatment with LC 5 . Additionally, the expression levels of P450 genes including CYP6CY14, CYP6CZ1, CYP6DC1, CYP6CY9, and CYP6DD1 were up-regulated in the exposed aphids. Taken together, our results show the hormetic effects of thiamethoxam on F 1 individuals, which might be due to the intermittent changes in expression of genes involved in fertility, growth and insecticide detoxification in A. gossypii., Competing Interests: Declaration of Competing Interest The authors have declared that they have no conflict of interest., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Buprofezin, a chitin synthesis inhibitor that can be used for the control of hemipteran pests, especially melon aphid, Aphis gossypii. The impact of low lethal concentrations of buprofezin on the biological parameters and expression profile of CHS1 gene were estimated for two successive generations of A. gossypii. The present result shows that the LC 15 and LC 30 of buprofezin significantly decreased the fecundity and longevity of both generations. Exposure of F 0 individuals to both concentrations delay the developmental period in F 1 . Furthermore, the survival rate, intrinsic rate of increase (r), finite rate of increase (λ), and net reproductive rate (R 0 ) were reduced significantly in progeny generation at both concentrations. However, the reduction in gross reproductive rate (GRR) was observed only at LC 30 . Although, the mean generation time (T) prolonged substantially at LC 30 . Additionally, expression of the CHS1 gene was significantly increased in F 0 adults. Significant increase in the relative abundance of CHS1 mRNA transcript was also observed at the juvenile and adult stages of F 1 generation following exposure to LC 15 and LC 30 . Therefore, our results show that buprofezin could affect the biological traits by diminishing the chitin contents owing to the inhibition of chitin synthase activity in the succeeding generation of melon aphid.

Competition is a key structuring component of biological communities, which is affected by both biotic and abiotic environmental stressors. Among the latter, anthropic stressors and particularly pesticides are noteworthy due to their intrinsic toxicity and large use in agroecosystems. However this issue has been scarcely documented so far. In this context, we carried out experiments under laboratory conditions to evaluate stress imposed by the neonicotinoid insecticide imidacloprid on intra and interspecific competition among two major wheat pest aphids. The bird cherry-oat aphid Rhopalosiphum padi L. and the English grain aphid Sitobion avenae F. were subjected to competition on wheat seedlings under varying density combinations of both species and subjected or not to imidacloprid exposure. Intraspecific competition does take place without insecticide exposure, but so does interspecific competition between both aphid species with R. padi prevailing over S. avenae. Imidacloprid interfered with both intra and interspecific competition suppressing the former and even the latter for up to 14 days, but not afterwards when a shift in dominance takes place favoring S. avenae over R. padi, in contrast with the interspecific competition without imidacloprid exposure. These findings hinted that insecticides are indeed able to mediate species interaction and competition influencing community structure and raising management concerns for favoring potential secondary pest outbreaks., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Cucurbitacin B is a natural triterpene present in plants of Cucurbitaceae family, which are among the host plants for melon aphid, Aphis gossypii. In present study we characterized the effects of two cucurbitacin B concentrations on the biological parameters of adults (F 0 ) and of juveniles and adults of their progeny (F 1 ). The results showed that cucurbitacin B at 25 ppm significantly reduced the adult longevity and fecundity of both F 0 and F 1 generation. Exposure of F 0 generation to 25 ppm though reduced the demographic traits of F 1 including the intrinsic rate of increase r (day -1 ), generation time T (day), finite rate of increase λ (day -1 ), however, only net reproductive rate R 0 (offspring/individual) decreased significantly. While 100 ppm reduced not only the longevity and fecundity of F 0 generation but also the longevity of F 1 generation. Fecundity of F 1 was not affected by 100 ppm of cucurbitacin B, however, R 0 (offspring/individual) and T (day) of F 1 generation were lower than the control population. These results support the hypothesis that high contents of cucurbitacin B caused negative impact on melon aphid and could be used as a lead for classical selection of resistant varieties of plants that are main hosts for the melon aphid.

Parasitoids are important natural enemies of aphids in wheat fields of northern China, and interest in them has increased in recent years. However, little is known regarding parasitoids of wheat aphids, which has hindered the study and understanding of aphid-parasitoid interactions. In the present study, three primary parasitoids and 15 hyperparasitoids were collected in wheat fields during a 2-year survey in northern China (2014, 2015) and a 2-year investigation at Langfang, Hebei Province (2015, 2016). Among them, Aphidius uzbekistanicus Luzhetski was found most frequently among the primary parasitoids, while Pachyneuron aphidis (Bouché) dominated the hyperparasitoid community. Investigation of the dynamics of wheat aphids and parasitoids revealed that the primary parasitoids appeared early in the growing period and that the hyperparasitoids appeared later. Analysis of the seasonal dynamics revealed that growth of the parasitoid population followed that of the aphid population and that the parasitism rates were highest in the late growing period.

Aphis gossypii Glover (Hemiptera: Aphididae) is a key pest in cotton crops, notably owing to its increasing resistance to commonly used pesticides. Such resistance prompts for the development of integrated pest management (IPM) programs that include novel pesticides being effective against the aphid. In the present study, we assessed lethal and sublethal effects of cycloxaprid, a novel chiral neonicotinoid pesticide developed in China, on A. gossypii. The lethal concentration at 50% (LC 50 ) value of cycloxaprid on A. gossypii was estimated, using the dipping method, at 7.73 mg/L. The impact of a sublethal concentration (LC 10 ) and a lethal concentration (LC 40 ) of cycloxaprid on A. gossypii population growth and feeding behavior (using electrical penetration graph technique [EPG]), and its transgenerational effect were further assessed. Adult longevity and fecundity significantly decreased after exposure to LC 40 or LC 10 of cycloxaprid. Cycloxaprid with sublethal concentrations (especially LC 40 ) had negative effects on phloem ingestion by A. gossypii. Additionally, the offspring of the adults exposed to LC 40 of cycloxaprid had shorter nymphal development duration and adult longevity than the control, and those from LC 10 and LC 40 treatments had lower adult fecundity and net productive rate. We demonstrated that cycloxaprid is a pesticide showing both lethal and sublethal activities, and transgenerational effects on A. gossypii; it may be useful for implementation in IPM programs against this aphid pest., (© 2016 Institute of Zoology, Chinese Academy of Sciences.)

Beta-cypermethrin has long been recommended as an effective pesticide to control the soybean aphid, Aphis glycines Matsumura, a serious pest in soybean crops. Besides acute toxicity, it leads to changes in life history traits of A. glycines, notably its reproductive potential. This study has assessed the effects of five sublethal concentrations (0.625, 1.25, 2.5, 5 and 10 µg/L) of beta-cypermethrin on different life history traits of A. glycines. Exposure to these concentrations caused shorter oviposition period and reduced adult longevity. The strongest stimulatory effect on aphid reproduction was achieved when exposed to a higher sublethal beta-cypermethrin concentration (5 µg/L). Net reproduction rate (R 0 ), intrinsic rate of increase (r m ) and finite rate of increase (λ) were significantly higher than that of the control, increasing by 20.58, 4.89 and 2.06%, respectively. We found no significant difference in mean generation time (T) between the treatment of 5 µg/L beta-cypermethrin and the control. However, when the concentration increased to 10 µg/L, the reproduction behavior was restrained and the mean generation time (T) was shortened, resulting in significant decrease in R 0 and T by 16.58 and 3.83%, respectively. In conclusion, a sublethal concentration (5 µg/L) of beta-cypermethrin triggered the strongest hormesis on A.glycines, thus providing valuable knowledge on the sublethal effects of this insecticide on soybean aphids. Hormesis may be one of the mechanisms underlying pest resurgences, and better knowledge would enable a more effective use of insecticides in Integrated Pest Management programs.

Background: The flower bug Orius sauteri (Poppius) (Hemiptera: Anthocoridae) is widely used as a biocontrol agent against thrips and aphids infesting greenhouse vegetables in Asia. The survival and oviposition of such predators, as well as the biocontrol services they provide, may be enhanced by adding extra floral resources to the crops. In the present study we investigated the effects of the plant Calendula officinalis L., used as a floral resource, for promoting the control of Myzus persicae (Sulzer) and Frankliniella occidentalis (Pergande) by O. sauteri under laboratory and greenhouse conditions., Results: Results showed that the presence of C. officinalis enhanced aphid and thrips suppression via an increased O. sauteri population growth. The predator populations responded positively to the addition of C. officinalis in the system, and they also varied as a function of the temperatures tested under laboratory conditions. In a similar way, predator populations varied among seasons, with the highest densities recorded in May in the greenhouse., Conclusion: C. officinalis can be used to increase available resources for natural enemies used in agricultural crops, notably in greenhouses. This study also provides evidence that increasing floral resources can enhance pest suppression provided by O. sauteri. © 2016 Society of Chemical Industry., (© 2016 Society of Chemical Industry.)

Sulfoxaflor is a novel insecticide belonging to sulfoximine chemical class that can be used to control sap-feeding insects, notably Aphis gossypii Glover. In addition to its acute toxicity, it is also important to consider the possible sublethal effects when establishing a comprehensive understanding of the toxicity of a new insecticide. We assessed the effects of a low lethal concentration (LC 25 ) of sulfoxaflor on biological parameters of A. gossypii adults (F0) and subsequent transgenerational effects, i.e., on the progeny (F1 generation). The data were analyzed using an age-stage life table procedure. The results showed that the longevity and fecundity were not significantly affected by the LC 25 of sulfoxaflor in the F0 or F1 generations. In addition, no significant differences were observed on the developmental time of each instar, the adult pre-oviposition period, and on the longevity of F1 individuals. However, the duration of their pre-adult stage and total pre-oviposition period, as well as their mean generation time were significantly increased. These observed effects affected aphid demographic traits; the survival rate, the intrinsic rate of increase (r i ), the finite rate of increase (λ), the net reproductive rate (R 0 ), and the gross reproduction rate (GRR) of the F1 individuals (i.e., from F0 mothers) were significantly lower compared to the control. Our results showed that sublethal effects of sulfoxaflor significantly slowed down A. gossypii population growth; they indicated that effects of sulfoxaflor might be increased (beyond lethal effect) through sublethal effects when concentrations decreased in sulfoxaflor-treated areas after initial application in field.

Top-down force is referred to arthropod pest management delivered by the organisms from higher trophic levels. In the context of prevalent adoption of transgenic Bt crops that produce insecticidal Cry proteins derived from Bacillus thuringiensis (Bt), it still remains elusive whether the top-down forces are affected by the insect-resistant traits that introduced into the Bt crops. We explored how Bt cotton affect the strength of top-down forces via arthropod natural enemies in regulating a non-target pest species, the cotton aphid Aphis gossypii Glover, using a comparative approach (i.e. Bt cotton vs. conventional cotton) under field conditions. To determine top-down forces, we manipulated predation/parasitism exposure of the aphid to their natural enemies using exclusion cages. We found that the aphid population growth was strongly suppressed by the dominant natural enemies including Coccinellids, spiders and Aphidiines parasitoids. Coccinellids, spiders and the assemblage of other arthropod natural enemies (mainly lacewings and Hemipteran bugs) are similarly abundant in both plots, but with the parasitoid mummies less abundant in Bt cotton plots compared to the conventional cotton plots. However, the lower abundance of parasitoids in Bt cotton plots alone did not translate into differential top-down control on A. gossypii populations compared to conventional ones. Overall, the top-down forces were equally strong in both plots. We conclude that transgenic Bt cotton does not disrupt the top-down forces regulating the cotton aphid in central China., Competing Interests: The authors have declared that no competing interests exist.

Spirotetramat is a novel tetramic acid-based insecticide, belonging to keto-enol pesticide family, with a novel mode of action; it interferes with lipid biosynthesis. Its insecticide activity against various agricultural pest insects have been demonstrated (e.g. on Myzus persicae, Bemisia tabaci and Tetranychus urticae). However, information available is currently limited on the efficacy of spirotetramat on the cotton aphid, Aphis gossypii, a key cotton pest worldwide. We assessed the spirotetramat toxicity on A. gossypii and evaluated its effects on aphid fecundity when exposed to a sublethal concentration (LC10) and to increasing lethal concentrations (LC25, LC50, and LC75). A key mechanism involved in insecticide resistance in aphids relates to esterase activity. We estimated the CarE activity and a CarE gene expression in aphids in response to spirotetramat exposure, then we tested tolerance of offspring to spirotetramat when the parents were exposed to the highest concentration tested in our study (LC75). Results showed that spirotetramat showed increasing toxicity to A. gossypii with exposure duration to treated leaves; LC50 ranged from 23,675.68 to 12.27 mg/L for 1 to 5-days exposure. In addition, spirotetramat reduced aphid daily fecundity, in all concentration treatments, especially with up to 90 % reduction in case of exposure to LC75. Total CarE activity increased dramatically and CarE mRNA expression was also up regulated in aphids after exposure to LC75 spirotetramat. Finally, the tolerance to spirotetramat in offspring (when parents were exposed to the LC75) showed a 2.5-fold increase when compared to control aphids. Consequently, spiroteramat showed potential for pest management of cotton aphids owing to both lethal and sublethal activities, notably strong impact on aphid fecundity. However, we also demonstrated that increased tolerance of A. gossypii to spirotetramat may happen through increased CarE- activity and subsequent metabolic degradation of the insecticide in aphids' body.

The wheat aphids, Rhopalosiphum padi (Linnaeus) and Sitobion avenae (Fabricius), are key pests on wheat crops worldwide. Management practices rely primarily on insecticides. The pirimicarb (carbamate) is used extensively as an effective insecticide to control these two aphids. In addition to the mortality caused by pirimicarb, various sublethal effects may occur in aphids when exposed to low lethal or sublethal doses. Understanding the general effect of pirimicarb on aphids could help increasing rational use of this insecticide. Under laboratory conditions, we assessed the sublethal effects of a low lethal concentration of pirimicarb (LC25) on biological traits and acetylcholinesterase (AChE) activity of R. padi and S. avenae. Both direct and transgenerational effects, i.e. on parent and the F1 generations were assessed, respectively. We found that R. padi and S. avenae responded differentially to the LC25 of pirimicarb. The parent generation of R. padi showed a 39% decrease in fecundity and multiple transgenerational effects were observed in the F1 generation; overall juvenile development, reproductive period, adult longevity and lifespan were longer than those of the control group. By contrast, LC25 of pirimicarb showed almost no effects on S. avenae biological traits in both the parent and F1 generations; only the pre-reproductive duration was reduced in F1 generations. Demographic parameter estimates (e.g. rm) showed similar trend, i.e. significant negative effect on R. padi population growth and no effect on S. avenae. However, AChE activity decreased in both R. padi and S. avenae treated by the LC25 of pirimicarb. We demonstrated sublethal and transgenerational effects of pirimicarb in the two wheat aphid species; it hinted at the importance of considering sublethal effects (including hormesis) of pirimicarb for optimizing Integrated Pest Management (IPM) of wheat aphids.

The soybean aphid, Aphis glycines Matsumura, is a major pest in soybean crop. Current management of this pest relies mainly on insecticides applications, and the neonicotinoid imidacloprid has been proposed as an effective insecticide to control A. glycines in soybean field. Imidacloprid at lethal concentrations not only exerts acute toxicity to A. glycines, but also cause various biological changes when aphids are chronically exposed to lower concentrations. In this study, we assessed the effects of a low-lethal (0.20 mg L(-1)) and two sublethal (0.05 and 0.10 mg L(-1)) imidacloprid concentrations on various A. glycines life history traits. Aphid exposure to 0.20 mg L(-1) imidacloprid caused slower juvenile development, shorter reproductive period, and reduced adult longevity, fecundity and total lifespan. Stimulatory effects, i.e. hormesis, on reproduction and immature development duration were observed in aphids exposed to the lower sublethal imidacloprid concentrations. Consequently, the net reproduction rate (R 0) was significantly higher than in the control aphids. These findings stress the importance of the actual imidacloprid concentration in its toxicological properties on A. glycines. Therefore, our results would be useful for assessing the overall effects of imidacloprid on A. glycines and for optimizing integrated pest management programs targeting this pest.

Sitobion avenae is a major agricultural pest of wheat in China. Using microsatellite markers, we studied the potential gene flow, genetic diversity, genetic differentiation, and genetic structure of seven S. avenae populations from different regions of China (Beijing, Hebei, Henan, Hubei, Jiangsu, Shandong, and Shanxi provinces). The populations from Henan, Shandong, and Jiangsu showed high levels of genic and genotypic diversity. By contrast, the genic diversity in the Beijing and Hebei populations was much lower. Despite this low genic diversity, the genotypic diversity of the Beijing population was higher than that of all of the other populations, except those from Jiangsu and Shandong. Overall, the genetic divergence among the seven S. avenae populations tested was high, though there was almost no differentiation between the Shandong and Henan populations. We observed significant negative correlation between the strength of gene flow and the geographic distances among populations. Based on genetic analysis, the seven S. avenae populations studied can be divided into four distinct clusters; (i) Hubei, (ii) Shanxi, (iii) Beijing and Hebei, and (iv) Shandong, Henan, and Jiangsu. The present results provide a basis for potentially optimizing integrated pest management (IPM) programs in China, through adapting control methods that target biological traits shared by various populations of the same genotype.

The cotton aphid Aphis gossypii Glover is the main aphid pest in cotton fields in the Yangtze River Valley Cotton-planting Zone (YRZ) in central China. Various natural enemies may attack the cotton aphid in Bt cotton fields but no studies have identified potential specific top-down forces that could help manage this pest in the YRZ in China. In order to identify possibilities for managing the cotton aphid, we monitored cotton aphid population dynamics and identified the effect of natural enemies on cotton aphid population growth using various exclusion cages in transgenic Cry1Ac (Bt)+CpTI (Cowpea trypsin inhibitor) cotton field in 2011. The aphid population growth in the open field (control) was significantly lower than those protected or restricted from exposure to natural enemies in the various exclusion cage types tested. The ladybird predator Propylaea japonica Thunberg represented 65% of Coccinellidae predators, and other predators consisted mainly of syrphids (2.1%) and spiders (1.5%). The aphid parasitoids Aphidiines represented 76.7% of the total count of the natural enemy guild (mainly Lysiphlebia japonica Ashmead and Binodoxys indicus Subba Rao & Sharma). Our results showed that P. japonica can effectively delay the establishment and subsequent population growth of aphids during the cotton growing season. Aphidiines could also reduce aphid density although their impact may be shadowed by the presence of coccinellids in the open field (likely both owing to resource competition and intraguild predation). The implications of these results are discussed in a framework of the compatibility of transgenic crops and top-down forces exerted by natural enemy guild.

Facultative bacterial endosymbionts can play an important role in the evolutionary trajectory of their hosts. Aphids (Hemiptera: Aphididae) are infected with a wide variety of facultative endosymbionts that can confer ecologically relevant traits, which in turn may drive microevolutionary processes in a dynamic selective environment. However, relatively little is known about how symbiont diversity is structured in most aphid species. Here, we investigate facultative symbiont species richness and prevalence among world-wide populations of the cowpea aphid, Aphis craccivora Koch. We surveyed 44 populations of A. craccivora, and detected 11 strains of facultative symbiotic bacteria, representing six genera. There were two significant associations between facultative symbiont and aphid food plant: the symbiont Arsenophonus was found at high prevalence in A. craccivora populations collected from Robinia sp. (locust), whereas the symbiont Hamiltonella was almost exclusively found in A. craccivora populations from Medicago sativa (alfalfa). Aphids collected from these two food plants also had divergent mitochondrial haplotypes, potentially indicating the formation of specialized aphid lineages associated with food plant (host-associated differentiation). The role of facultative symbionts in this process remains to be determined. Overall, observed facultative symbiont prevalence in A. craccivora was lower than that of some other well-studied aphids (e.g., Aphis fabae and Acyrthosiphon pisum), possibly as a consequence of A. craccivora's almost purely parthenogenetic life history. Finally, most (70 %) of the surveyed populations were polymorphic for facultative symbiont infection, indicating that even when symbiont prevalence is relatively low, symbiont-associated phenotypic variation may allow population-level evolutionary responses to local selection.

The soybean aphid, Aphis glycines Matsumura, has become the single most important arthropod pest of soybeans in North America. Native to Asia, this invasive species was first discovered in North America in July 2000 and has rapidly spread throughout the northcentral United States, much of southeastern Canada, and the northeastern United States. In response, important elements of the ecology of the soybean aphid in North America have been elucidated, with economic thresholds, sampling plans, and chemical control recommendations widely adopted. Aphid-resistant soybean varieties were available to growers in 2010. The preexisting community of aphid natural enemies has been highly effective in suppressing aphid populations in many situations, and classical biological control efforts have focused on the addition of parasitoids of Asian origin. The keys to sustainable management of this pest include understanding linkages between the soybean aphid and other introduced and native species in a landscape context along with continued development of aphid-resistant varieties.

The host specificity of insect parasitoids and herbivores is thought to be shaped by a suite of traits that mediate host acceptance and host suitability. We conducted laboratory experiments to identify mechanisms shaping the host specificity of the aphid parasitoid Binodoxys communis. Twenty species of aphids were exposed to B. communis females in microcosms, and detailed observations and rearing studies of 15 of these species were done to determine whether patterns of host use resulted from variation in factors such as host acceptance or variation in host suitability. Six species of aphids exposed to B. communis showed no signs of parasitism. Four of these species were not recognized as hosts and two effectively defended themselves from attack by B. communis. Other aphid species into which parasitoids laid eggs had low suitability as hosts. Parasitoid mortality occurred in the egg or early larval stages for some of these hosts but for others it occurred in late larval stages. Two hypotheses explaining low suitability were investigated in separate experiments: the presence of endosymbiotic bacteria conferring resistance to parasitoids, and aphids feeding on toxic plants. An association between resistance and endosymbiont infection was found in one species (Aphis craccivora), and evidence for the toxic plant hypothesis was found for the milkweed aphids Aphis asclepiadis and Aphis nerii. This research highlights the multifaceted nature of factors determining host specificity in parasitoids.

The term 'idiobiont' refers to those parasitoid species that permanently paralyse their hosts during parasitism, causing the cessation of host growth and development. This is in contrast to koinobiont parasitoids, which allow their hosts to continue developing after being parasitized. While no koinobiont species induce permanent paralysis in their hosts, a minority of koinobionts induce a temporary paralysis that does not interfere with overall host growth and development. We characterized transient paralysis induction in two koinobiont aphid parasitoids in the genus Binodoxys (Hymenoptera: Aphidiinae). Both Binodoxys species induced transient paralysis in Aphis glycines, with paralysis time ranging between 4.5 and 8 min (depending upon parasitoid species and host instar). In a separate experiment, B. communis was capable of inducing transient paralysis in nine aphid species. We addressed two hypotheses potentially explaining the adaptive value of temporary host paralysis in experiments using A. nerii, which is readily accepted but engages in strong defensive behaviour. The first hypothesis is that paralysis increases oviposition success by interfering with host defences and the second is that it aids in the avoidance of self-superparasitism. Paralysed aphids were more likely to be rejected by B. communis than were aphids that had never been stung or that had recovered from paralysis. This result supports the avoidance-of-self-superparasitism hypothesis and is inconsistent with the hypothesis that transient paralysis increases oviposition success of B. communis.

Generalist insect predators can significantly impact the dynamics of pest populations; and, using alternative prey, they can rapidly establish in disturbed agroecosystems. However, indirect interactions between prey can occur, leading to either increased or decreased predation on focal prey. The present paper demonstrates how alternative prey can disrupt predation by the hemipteran Orius insidiosus on the soybean aphid Aphis glycines via short-term indirect interactions. We used laboratory microcosms to measure the impact of the predator on the population growth of the aphid in the presence of alternative prey, soybean thrips Neohydatothrips variabilis, and we characterized the foraging behaviour of the predator to assess prey preference. We showed that O. insidiosus predation on aphids was reduced in the presence of thrips and that this positive impact on aphids increased as thrips density increased. Results from the behavioural experiment support the hypothesis of a prey preference toward thrips. When prey-pest ratio is aphid-biased, short-term apparent commensalism between prey occurs in favour of the most abundant prey (aphids) with no switching behaviour appearing in O. insidiosus. These results demonstrate that potential indirect interactions should be taken into account when considering O. insidiosus as a biocontrol agent against the soybean aphid.

The Asian parasitoid, Binodoxys communis (Gahan) (Hymenoptera: Braconidae), is a candidate for release against the exotic soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), in North America. In this study, we examined preferences by B. communis for the different developmental stages of A. glycines and investigated consequences of these preferences for parasitoid fitness. We also determined to what extent aphid defensive behaviours mediate such preferences. We found that B. communis readily attacks and successfully develops in the different A. glycines developmental stages. Binodoxys communis development time gradually increased with aphid developmental stage, and wasps took longest to develop in alates. An average (+/-SE) of 54.01+/-0.08% of parasitized A. glycines alatoid nymphs transformed into winged adult aphids prior to mummification. No-choice assays showed a higher proportion of successful attacks for immature apterous A. glycines nymphs compared to adults and alatoid nymphs. Also, choice trials indicated avoidance and lower attack and oviposition of adults and alatoid nymphs. The different aphid stages exhibited a range of defensive behaviours, including body raising, kicking and body rotation. These defenses were employed most effectively by larger aphids. We discuss implications for the potential establishment, spread and biological control efficacy of A. glycines by B. communis in the event that it is released in North America.

The soybean aphid, Aphis glycines (Hemiptera: Aphididae), is a pest of soybeans in Asia, and in recent years has caused extensive damage to soybeans in North America. Within these agroecosystems, generalist predators form an important component of the assemblage of natural enemies, and can exert significant pressure on prey populations. These food webs are complex and molecular gut-content analyses offer nondisruptive approaches for examining trophic linkages in the field. We describe the development of a molecular detection system to examine the feeding behaviour of Orius insidiosus (Hemiptera: Anthocoridae) upon soybean aphids, an alternative prey item, Neohydatothrips variabilis (Thysanoptera: Thripidae), and an intraguild prey species, Harmonia axyridis (Coleoptera: Coccinellidae). Specific primer pairs were designed to target prey and were used to examine key trophic connections within this soybean food web. In total, 32% of O. insidiosus were found to have preyed upon A. glycines, but disproportionately high consumption occurred early in the season, when aphid densities were low. The intensity of early season predation indicates that O. insidiosus are important biological control agents of A. glycines, although data suggest that N. variabilis constitute a significant proportion of the diet of these generalist predators. No Orius were found to contain DNA of H. axyridis, suggesting intraguild predation upon these important late-season predators during 2005 was low. In their entirety, these results implicate O. insidiosus as a valuable natural enemy of A. glycines in this soybean agroecosystem.

Neurotoxic pyrethroid insecticides are widely used for crop protection, and lethal and sublethal perturbations can be expected in beneficial insects. Under laboratory conditions, the lethal and sublethal effects of deltamethrin on the aphid parasitoid Diaeretiella rapae M'Intosh (Hymenoptera: Braconidae) were studied at the mummy stage and in emerging adults. Following a multistep bioassay, analyses were aimed at evaluating the effects of deltamethrin at various crucial steps in the recolonization process following a deltamethrin treatment: Parasitoid pupal development (emergence from the mummies), adult survival, and host-searching capacity. A four-armed olfactometer was used to investigate the effect of deltamethrin on host-searching behavior (a range of concentrations causing 0.4-79.4% mortality was tested), and a Potter tower was used to test the deltamethrin effect with a realistic application method (four concentrations were tested: 0.5, 5.0, 6.25, and 50 g active ingredient [a.i.]/ha). Deltamethrin reduced the percentage of emergence from mummies, but only when exposed to the 50 g a.i./ha concentration. However, for all concentrations tested, the insecticide induced a decrease in longevity after emergence from sprayed mummies and significant adult mortality when parasitoids walked on fresh residues on leaves. Indices were defined and predicted a high mortality and, thus, reduction of recolonization capacities. However, deltamethrin had no effect on orientation behavior toward aphid-infested plants for adults that survived a residual exposure to the insecticide. The impact of deltamethrin on recolonization via pupal emergence and interest in the methodology used are discussed.

In fall, Myzus persicae (Sulzer) (Homoptera: Aphididae) may exhibit population resurgence in winter oilseed rape in France. This resurgence may arise from pyrethroid treatments against Coleoptera (Psylliodes chrysocephala L.) that either kill parasitoids present during treatment or prevent recolonization by off-crop parasitoids. We studied the impact of Diaeretiella rapae (M'Intosh) (Hymenoptera: Braconidae) on populations of M. persicae when parasitoids were introduced on deltamethrin-treated plants at increasing intervals after treatment. Parasitoids were introduced 1, 2, 7, or 14 d posttreatment on individually caged plants infested with established populations of M. persicae. Aphids were counted 7, 14 and 21 d after parasitoid introduction. First, we observed that both the pesticide and the parasitoid reduced aphid population growth and that their effects were additive. Second, there was no mortality of parasitoids exposed to treated leaves in a device with a refuge area, and only 20% of mortality without the refuge area. Furthermore, deltamethrin residues had no effect on the reproduction of D. rapae females. Compared with the known toxicity of deltamethrin to D. rapae on glass, this low mortality may have been due to both the high liposolubility of deltamethrin (leading to a rapid diffusion of residues in the oilseed rape leaf cuticle) and to the existence of a refuge area. This work suggests that D. rapae could limit populations of M. persicae in the fall, even after pyrethroid treatment, because the presence of deltamethrin residues had little impact on the parasitoid.

In many parasitoid species, the recognition of chemical signals is essential to find specific hosts. This function is often impaired by exposure to insecticides that are usually neurotoxic. The behaviour of the Hymenopterous parasitoid Aphidius ervi (Haliday) (Hymenoptera: Aphidiinae) after surviving low doses of the pyrethroid lambda-cyhalothrin was examined in laboratory conditions. The host aphid was Myzus persicae (Sulzer) (Homoptera: Aphididae) on oilseed rape. Parasitoid females were exposed by contact with dry residues of the active ingredient at a lethal dose, LD20, and a sub-lethal dose, LD0.1. In a four-armed olfactometer, untreated and inexperienced females were attracted by the odour of M. persicae-infested plants and previous oviposition experience increased the duration of the attraction response. The response of inexperienced females decreased after an exposure to LD0.1 but not to LD20. No effect was observed when females had an oviposition experience prior to the olfactometer test. The oviposition activity was significantly decreased in the LD20-treated group but not in the LD0.1-treated one. All effects disappeared within 24h. Our work shows that orientation and oviposition behaviours may be impaired by low doses of lambda-cyhalothrin, depending on the dose, the parasitoid experience and the type of behaviour.

Parasitism rates and parasitoid development can be influenced by the species and developmental stage of the host, both of these factors can influence parasitoid performance and fitness. In this study, parasitism rates and developmental parameters were assessed for two widely distributed and commercially available species of aphid parasitoid: Aphidius ervi (Hymenoptera: Braconidae) and Aphelinus abdominalis (Hymenoptera: Aphelinidae). In a first bioassay, parasitism rates and parasitoid development were investigated in different host species. The wasp A. ervi was tested on Macrosiphum euphorbiae, Rhopalosiphum padi, and Myzus persicae (Hemiptera: Aphididae) and A. abdominalis was tested on M. persicae, R. padi, and Rhopalosiphum maidis (Hemiptera: Aphididae). The results indicated that A. ervi had a greater percentage of emergence, higher percentage of parasitized aphids, longer developmental time, and higher proportion of females in M. persicae than in the other hosts. A. abdominalis had a greater percentage of emergence, larger progeny, and shorter developmental time in R. padi than in the other hosts. A second bioassay evaluated the preference of the parasitoids for different instars of their respective optimum host aphids in terms of parasitism and development, as determined in the first bioassay. The results showed that A. ervi produced a greater number of mummies in the fourth instar and in adults of M. persicae. In contrast, A. abdominalis preferred the first instar of R. padi. In conclusion, our results indicate that both parasitoid species exhibit different parasitism parameters depending upon the host species and the host stage. This suggests that these parasitoid species could be potentially complementary on multiple or combined releases of biological control programs. [ABSTRACT FROM AUTHOR]

Neurotoxic insecticides are widely used for crop protection and behavioural perturbations can be expected in surviving beneficial insects, including parasitoids of pest insects. The present study aims to investigate the relationship between the dose of insecticide parasitoids have been exposed to, and the subsequent ability of these parasitoids to respond to host-related cues. A four-armed olfactometer, a design widely used to observe orientation responses in various insects and parasitoids in particular, was chosen to investigate the dose–response relationship. The species studied was Aphidius ervi, a relatively generalist parasitoid of aphids, and commercialised for biological control and integrated pest management. Active ingredients with similar and different modes of action on the nervous system were compared: a pyrethroid (lambda-cyhalothrin), an organophosphate (chlorpyrifos), a carbamate (pirimicarb) and a carbamyltriazole (triazamate). Adult females were exposed to dry residues on glass for 24 h. LD50 were calculated and predicted a high risk of mortality at the field application rate. The effect of five increasing residual doses of each active ingredient was tested on responses to plant-host odour in the olfactometer, from sublethal doses to LD50, and up to LD70 for some products. It appeared that none of the doses of lambda-cyhalothrin, chlorpyriphos and pirimicarb had any effect on A. ervi responses to the odour from the aphid-infested plant (Myzus persicae on oilseed rape). But for triazamate, a significant dose–behavioural response was quantified and attraction to the odour was no longer significant in females surviving the LD50. The possible explanations for the presence or absence of effect, depending on the insecticide are discussed. [Copyright &y& Elsevier]