Hormesis effects of sulfoxaflor on Aphis gossypii feeding, growth, reproduction behaviour and the related mechanisms

Sublethal and hormetic effects of the fungicide tebuconazol on the biology of a nontarget pest insect, Musca domestica

Lethal levels of pesticides gradually decrease after application in field crops due to several environmental factors, thereby causing sublethal exposure to nontarget species. Sublethal exposure to pesticides may have negative, neutral and/or stimulatory (hormetic) effects on the biology of exposed organisms. Although fungicidal applications in field crops have been reported to cause side effects in different nontarget species through sublethal exposure, reports on the side effects of fungicide on nontarget insect species are limited. Musca domestica, an insect pest for public health and animal agriculture, is one of the most common nontarget insect species in cropping areas. This work aimed to study sublethal effects of the fungicide tebuconazol on key life history traits of M. domestica. The results of the present study revealed that, after five generations of exposure to LD5, LD10 and LD20 of tebuconazol, M. domestica showed hormetic response to LD5 and non-hormetic response to LD10 and LD20 in terms of the performance of most of the biological traits and population/demographic parameters. For example, the development of immature stages was faster in the LD5 treatment than in the control, LD10 and LD20 treatments. The performance of other biological traits such as longevity, preoviposition period, oviposition days, fecundity and preadult survival rates, was better than that of the other treatments. Similarly, the finite rate of increase, intrinsic rate of increase and net reproductive rate were greater in the LD5 treatment than in other treatment groups. In addition, the mean generation time was the lowest in the LD5 treatment, while it was the highest in the LD20 treatment of tebuconazol. Low lethal exposure of tebuconazol to M. domestica under field conditions may favor its resurgence and population expansion in and/or around cropping areas, thereby increasing the probability of fly borne diseases.

Toxicity and Sublethal Effects of Lambda-Cyhalothrin Insecticide on Parent and Filial Generations of Henosepilachna vigintioctomaculata (Coleoptera: Coccinellidae)

Lambda-cyhalothrin is a synthetic pyrethroid insecticide that is widely used to control leaf-eating pests. Because of increased insecticide resistance, an understanding of sublethal cross-generational effects of insecticides is important. We examine the effects of sublethal concentrations (SLCs) (LC10, LC20, and LC40) of lambda-cyhalothrin on the growth, reproduction, and detoxification enzyme activities of F0 and F1 generation Henosepilachna vigintioctomaculata. Lambda-cyhalothrin is toxic to adult H. vigintioctomaculata, with an LC40 at 48 h of 0.355 mg L-1. At SLCs, lambda-cyhalothrin significantly reduces the longevity and average fecundity of F0 and F1 adults, and prolongs the durations of the egg, larval, and pupal stages and adult preoviposition period. Additionally, an increased lambda-cyhalothrin concentration significantly decreases net reproductive rates, and both finite and intrinsic rates of increase in the F1 generation, and significantly increases the average generation cycle. The detoxification enzyme activity of F1 adults treated with SLCs of lambda-cyhalothrin for 48 h trends upwards. Results indicate that low concentrations of lambda-cyhalothrin induce glutathione S-transferase and carboxylesterase activities and inhibit multifunctional oxidase activity. The growth, development, and reproduction of the H. viltioctomaculata F1 population remain inhibited by lambda-cyhalothrin treatment in the adult stage, and inhibitory effects increase with increased lambda-cyhalothrin concentration. The control efficacy of lambda-cyhalothrin against H. viltioctomaculata shows cross-generational effects.

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

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

Ecological risks of a biopesticide from marine-derived amino-oligosaccharides in agriculture: Food chain effects on non-target organisms Frankliniella occidentalis and its natural predator Neoseiulus barkeri

A biopesticide from marine-derived amino-oligosaccharides (AO) are extensively utilized in China, yet there is a lack of scientific literature on their potential ecological risks when transmitted through the food chain to Neoseiulus barkeri, a natural predator of Frankliniella occidentalis. In this study, we conducted a comprehensive investigation into the food chain effects of AO on both F. occidentalis and N. barkeri. Our findings indicate that AO-treated cucumber leaves facilitated the population growth of F. occidentalis but indirectly suppressed the fecundity of N. barkeri which fed on the first instar nymphs of F. occidentalis. Besides, F. occidentalis that ingested AO-treated cucumber leaves exhibited elevated levels of total protein and defense enzymes, including catalase (CAT) and peroxidase (POD), whereas the detoxification enzymes activity, such as carboxylesterase (CarE) and cytochrome P450 monooxygenase (P450), was diminished. Conversely, N. barkeri exhibited decreased levels of the defense enzymes superoxide dismutase (SOD) and POD, coupled with an elevated CarE activity, because of AO food chain transmission. In conclusion, the food chain effects of AO on non-target organisms F. occidentalis and N. barkeri may involve the modulation of defense and detoxification enzyme activities, leading to varying fitness costs. These findings provide critical insights for agricultural pest management strategies, highlighting the necessity of evaluating the effects of AO on non-target organisms within ecosystems, especially beneficial insects, during its application.

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

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

Agricultural insect pests as models for studying stress-induced evolutionary processes

Agricultural insect pests (AIPs) are widely successful in adapting to natural and anthropogenic stressors, repeatedly overcoming population bottlenecks and acquiring resistance to intensive management practices. Although they have been largely overlooked in evolutionary studies, AIPs are ideal systems for understanding rapid adaptation under novel environmental conditions. Researchers have identified several genomic mechanisms that likely contribute to adaptive stress responses, including positive selection on de novo mutations, polygenic selection on standing allelic variation and phenotypic plasticity (e.g., hormesis). However, new theory suggests that stress itself may induce epigenetic modifications, which may confer heritable physiological changes (i.e., stress-resistant phenotypes). In this perspective, we discuss how environmental stress from agricultural management generates the epigenetic and genetic modifications that are associated with rapid adaptation in AIPs. We summarise existing evidence for stress-induced evolutionary processes in the context of insecticide resistance. Ultimately, we propose that studying AIPs offers new opportunities and resources for advancing our knowledge of stress-induced evolution.

Tetraniliprole risk assessment: Unveiling a hidden threat for managing a generalist herbivore

Insecticide resistance poses a significant challenge in managing generalist herbivores such as the tobacco cutworm (TCW), Spodoptera litura. This study investigates the potential risks associated with using the novel diamide insecticide tetraniliprole to control TCW. A tetraniliprole-resistant strain was developed through twelve generations of laboratory selection, indicating an intermediate risk of resistance development. Field monitoring in China revealed a significant incidence of resistance, particularly in the Nanchang (NC) population (>100-fold). Tetraniliprole showed moderate to high cross-resistance to multiple insecticides and was autosomally inherited with incomplete dominance, controlled by multiple genes, some of which belong to the cytochrome P450 family associated with enhanced detoxification. Life table studies indicated transgenerational hormesis, stimulating TCW female fecundity and increasing population net reproduction rates (R0). These findings suggest a potential for pest resurgence under tetraniliprole use. The integrated risk assessment provides a basis for the sustainable management of TCW using tetraniliprole.

The low-lethal concentrations of rotenone and pyrethrins suppress the population growth of Rhopalosiphum padi

As an important pest on winter wheat, Rhopalosiphum padi (L.) causes damage to the wheat yield by sucking plant nutrients, transmitting plant viruses and producing mildew. R. padi has been reported to develop resistance to pyrethroids and neonicotinoids. To explore potential alternative approaches for R. padi control, the activity of 10 botanical insecticides was evaluated. Results suggested that the toxicity of rotenone and pyrethrins to R. padi were the highest and near to the commonly used chemical insecticides. When exposed to the low-lethal concentrations (LC10, LC30) of rotenone or pyrethrins for 24 h, the lifespan and fecundity of adults in F0 generation decreased significantly compared to control. The negative effect could also be observed in the F1 generation, including the decreased average offspring, longevity of adult, and prolonged nymph period. The population parameters in F1 generation of R. padi were also inhibited by exposing to the low-lethal concentrations of rotenone or pyrethrins, including the decreased net reproductive rate, intrinsic rate of natural increase, finite rate of population increase, and gross reproduction rate. Co-toxocity factor results showed that mixtures of rotenone and thiamethoxam, pyrethrins and thiamethoxam showed synergistic effect. Our work suggested that rotenone and pyrethrins showed negative effect on the population growth under low-lethal concentrations. They are suitable for R. padi control as foliar spraying without causing population resurgence.

Key residues involved in the interaction between chlorpyrifos and a chemosensory protein in Rhopalosiphum padi: Implication for tracking chemical residues via insect olfactory proteins

The development of advanced biosensors for tracking chemical residues and detecting environmental pollution is of great significance. Insect chemical sensory proteins, including chemosensory proteins (CSPs), are easy to synthesize and purify and have been used to design proteins for specific biosensor applications. Chlorpyrifos is one of the most commonly used chemicals for controlling insect pests in agriculture. This organophosphate is harmful to aquatic species and has long-term negative consequences for the ecosystem. CSPs can bind and carry a variety of environmental chemicals, including insecticides. However, the mechanism by which CSPs bind to insecticides in aphids has not been clarified. In this study, we discovered that RpCSP1 from Rhopalosiphum padi has a higher affinity for chlorpyrifos, with a Ki value of 4.763 ± 0.491 μM. Multispectral analysis revealed the physicochemical binding mechanism between RpCSP1 and chlorpyrifos. Computational simulation analysis demonstrated that the main factor promoting the development of the RpCSP1-chlorpyrifos complex is polar solvation energy. Four residues (Arg33, Glu94, Gln145, Lys153) were essential in facilitating the interaction between RpCSP1 and chlorpyrifos. Our research has improved knowledge of the relationship between CSPs and organophosphorus pesticides. This knowledge contributes to the advancement of biosensor chips for tracking chemical residues and detecting environmental pollution through the use of CSPs.