Effects of exposure to imidacloprid direct and poisoned cotton aphids Aphis gossypii on ladybird Hippodamia variegata feeding behavior

Silencing the rhythm gene AgCLK-1 reduced feeding of Aphis gossypii

The cotton aphid Aphis gossypii Glover is an important cotton pest, and means of controlling this insect is a primary research focus. Although biological rhythm is an important mechanism that regulates numerous insect processes and activities, its role in cotton aphid has not been elucidated. In the present study, four highly-expressed circadian rhythm genes were selected from the cotton aphid genome database and their physicochemical properties and protein structures were analyzed. These genes were in the Takeout, Timeless, and Timeless interacting-related families, and the corresponding proteins contained highly-conserved Swis and TIMELESS domains. Gene expression analysis at multiple developmental stages revealed differing expression patterns between the four genes. AgCLK-1 had the highest relative expression of the four, especially during the nymph period. Silencing AgCLK-1 caused a significant refusal of the cotton aphids to feed at 1, 3, and 5 d of treatment. These results demonstrated that AgCLK-1 played a key role in regulating the feeding behavior of cotton aphid. This new functional understanding provides novel insights into cotton aphid biology and suggests new targeting strategies for agricultural pest control.

Aphid Resistance Evaluation and Constitutive Resistance Analysis of Eighteen Lilies

Lilies (Lilium spp.) are famous bulb flowers worldwide, with high ornamental value. Aphid damage has seriously constrained the development of the lily industry. In this study, the aphid resistance of 16 lily cultivars and 2 wild lily species was characterized in the field and greenhouse. Leaf color parameters, stomatal density and size, thickness of leaf layers, leaf waxy content, and leaf water content were determined to explore the constitutive resistance of lilies. The results show that there was a significant positive correlation between the number of aphids in the field and in the greenhouse (p ≤ 0.05, r = 0.47). This indicated that the level of aphid infestation in both the field and the greenhouse is generally consistent across different types of lily plants. Among these 18 lilies, 'Palazzo', 'Nymph', 'Cameleon' and L. lancifolium were resistant to A. gossypii, while 'Black Beauty' and 'Magnefique' had poor resistance. The correlation analysis results showed that the number of aphids was negatively correlated with leaf abaxial surface a*, stomatal size, water content, and thickness of leaf palisade tissue and positively correlated with leaf distal axial surface b*, C*, and waxy content. Among them, the correlation between the number of aphids and the thickness of leaf palisade tissue reached a significant level (p ≤ 0.05, r = -0.521). This indicated that the thickness of the palisade tissue of lily leaves might be an important factor influencing the proliferation of aphids. This study not only screened out aphid-resistant lilies but also established a crucial research foundation for the targeted breeding and molecular breeding of lilies with aphid resistance.

Field-realistic exposure to neonicotinoid and sulfoximine insecticides impairs visual and olfactory learning and memory in Polistes paper wasps

Exposure to insecticides may contribute to global insect declines due to sublethal insecticide effects on non-target species. Thus far, much research on non-target insecticide effects has focused on neonicotinoids in a few bee species. Much less is known about effects on other insect taxa or newer insecticides, such as sulfoxaflor. Here, we studied the effects of an acute insecticide exposure on both olfactory and visual learning in free-moving Polistes fuscatus paper wasps. Wasps were exposed to a single, field-realistic oral dose of low-dose imidacloprid, high-dose imidacloprid or sulfoxaflor. Then, visual and olfactory learning and short-term memory were assessed. We found that acute insecticide exposure influenced performance, as sulfoxaflor- and high-dose imidacloprid-exposed wasps made fewer correct choices than control wasps. Notably, both visual and olfactory performance were similarly impaired. Wasps treated with high-dose imidacloprid were also less likely to complete the learning assay than wasps from the other treatment groups. Instead, wasps remained stationary and unmoving in the testing area, consistent with imidacloprid interfering with motor control. Finally, wasps treated with sulfoxaflor were more likely to die in the week after treatment than wasps in the other treatment groups. Our findings demonstrate that sublethal, field-realistic dosages of both neonicotinoid- and sulfoximine-based insecticides impair wasp learning and short-term memory, which may have additional effects on survival and motor functioning. Insecticides have broadly detrimental effects on diverse non-target insects that may influence foraging effectiveness, pollination services and ecosystem function.

Evaluation of Transgenerational Effects of Sublethal Imidacloprid and Diversity of Symbiotic Bacteria on Acyrthosiphon gossypii

Symbiotic bacteria and hormesis in aphids are the driving forces for pesticide resistance. However, the mechanism remains unclear. In this study, the effects of imidacloprid on the population growth parameters and symbiotic bacterial communities of three successive generations of Acyrthosiphon gossypii were investigated. The bioassay results showed that imidacloprid had high toxicity to A. gossypii with an LC₅₀ of 1.46 mg·L^-1. The fecundity and longevity of the G0 generation of A. gossypii decreased when exposed to the LC₁₅ of imidacloprid. The net reproductive rate (R₀), intrinsic rate of increase (r_m), finite rate of increase (λ), and total reproductive rate (GRR) of G1 and G2 offspring were significantly increased, but those of the control and G3 offspring were not. In addition, sequencing data showed that the symbiotic bacteria of A. gossypii mainly belonged to Proteobacteria, with a relative abundance of 98.68%. The dominant genera of the symbiotic bacterial community were Buchnera and Arsenophonus. After treatment with the LC₁₅ of imidacloprid, the diversity and species number of bacterial communities of A. gossypii decreased for G1-G3 and the abundance of Candidatus-Hamiltonella decreased, but Buchnera increased. These results provide insight into the resistance mechanism of insecticides and the stress adaptation between symbiotic bacteria and aphids.

Life-table parameters, functional response, flight ability, and cross-generational effects of matrine demonstrate its safety to Hippodamia variegata (Coleoptera: Coccinellidae)

In Xinjiang's cotton growing area of China, previous studies have shown that matrine is a selective botanical insecticide, with high toxicity to Aphis gossypii Glover (Hemiptera: Aphididae) and low toxicity to its dominant natural enemy, Hippodamia variegata Goeze (Coleoptera: Coccinellidae). However, lethal effects alone are not sufficient evidence to justify introducing matrine into local IPM strategies. In this context, we systematically evaluated the safety of matrine to H. variegata by investigating the effects of contact and stomach toxicity of matrine on the lady beetle's life-table parameters, predatory ability, flight ability of parental adults, and cross-generational effects on life-table parameters of the predator's offspring. We found that matrine at 2,000 mg/l did not have any significant negative effects to adult fecundity, longevity, or the predatory capacity of parental adults of H. variegata. Moreover, it is the same for cross-generational effects of matrine on H. variegate. The contact toxicity of matrine significantly reduced the flight time of H. variegata males, but did not significantly affect flight time and average velocity. Our results support the view that matrine is safe to H. variegata and can be recommended for use in the local IPM strategy for control of A. gossipii.

Exposure to flupyradifurone affect health of biocontrol parasitoid Binodoxys communis (Hymenoptera: Braconidae) via disrupting detoxification metabolism and lipid synthesis

Assessing the potential effects of insecticides on beneficial biological control agents is key to facilitating the success of integrated pest management (IPM) approaches. Flupyradifurone (FPF) is a novel neonicotinoid insecticide that is replacing traditional neonicotinoids over a large geographical range to control pests. Binodoxys communis, is the dominant parasitic natural enemy of aphids. To date, no reports have addressed sublethal effects of FPF on B. communis. In this study, the lethal and sublethal effects of FPF on B. communis were investigated by indirect exposure to larvae and direct exposure to adults. Results showed that the sublethal LC₁₀ and LC₂₅ of FPF had negative effects on the biological parameters of B. communis, including significantly reducing survival rate, adult longevity, parasitism rate, and emergence rate, and significantly prolonging the developmental stages from egg to cocoons. In addition, we observed a transgenerational effect of FPF on the next generation (F1). RNA-Seq transcriptomic analysis identified a total of 1429 differentially expressed genes (DEGs) that were significantly changed between FPF-treated and control groups. These DEGs are mainly enriched in metabolic pathways such as peroxisomes, glutamate metabolism, carbon metabolism, fatty acid metabolism, and amino acid metabolism. This report is the first comprehensive evaluation of how FPF effects B. communis, which adds to the methods of assessing pesticide exposure in parasitic natural enemies. We speculate that the significant changes in pathways, especially those related to lipid synthesis, may be the reason for weakened parasitoid biocontrol ability. The present study provides new evidence for the toxic effects and environmental residue risk of FPF.

Identification of Active Species in Photodegradation of Aqueous Imidacloprid over g-C3N4/TiO2 Nanocomposites

In this work, g-C3N4/TiO2 composites were fabricated through a hydrothermal method for the efficient photocatalytic degradation of imidacloprid (IMI) pesticide. The composites were fabricated at varying loading of sonochemically exfoliated g-C3N4 (denoted as CNS). Complementary characterization results indicate that the heterojunction between the CNS and TiO2 formed. Among the composites, the 0.5CNS/TiO2 material gave the highest photocatalytic activity (93% IMI removal efficiency) under UV-Vis light irradiation, which was 2.2 times over the pristine g-C3N4. The high photocatalytic activity of the g-C3N4/TiO2 composites could be ascribed to the band gap energy reduction and suppression of photo-induced charge carrier recombination on both TiO2 and CNS surfaces. In addition, it was found that the active species involved in the photodegradation process are OH• and holes, and a possible mechanism was proposed. The g-C3N4/TiO2 photocatalysts exhibited stable photocatalytic performance after regeneration, which shows that g-C3N4/TiO2 is a promising material for the photodegradation of imidacloprid pesticide in wastewater.

Effects on Life-History Traits of Hypogastrura viatica (Collembola) Exposed to Imidacloprid Through Soil or Diet

Collembola (springtails) are important members of soil communities worldwide by contributing to degradation of organic matter. In nature, Collembola might be exposed to the neonicotinoid insecticide imidacloprid, which is fairly persistent in soil. We exposed the widespread Hypogastrura viatica to imidacloprid through soil or food and monitored the animals during exposure and a post exposure period. We recorded effects on life-history traits affecting individual fitness, that is, mortality, behavioral activity, several reproduction traits, and molting frequency. Exposure through soil led to a concentration-dependent mortality, while the mortality from dietary exposure possibly reflected reduced feeding activity. The body burden of imidacloprid in the Collembola did not differ between treatments. We found no sign of recovery in behavioral activity following exposure in either experiment. The egg production of H. viatica was not significantly affected by imidacloprid at 0.01 mg/kg dry soil but showed a tendency to reduce number of eggs per batch and reduced hatching success. At higher concentrations, reproduction was close to, or completely, stopped. The molting frequency decreased during exposure, while in the post exposure period, we saw milder effects at the highest concentrations, suggesting elimination through molting or reduced toxic response as a result of reduced feeding activity. Overall, H. viatica was more sensitive to imidacloprid than previously studied Collembola, which highlights the importance of considering species sensitivities when risk-assessing soil environments. Environ Toxicol Chem 2021;40:3111-3122. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

In Silico Studies of Lamiaceae Diterpenes with Bioinsecticide Potential against Aphis gossypii and Drosophila melanogaster

Background: The growing demand for agricultural products has led to the misuse/overuse of insecticides; resulting in the use of higher concentrations and the need for ever more toxic products. Ecologically, bioinsecticides are considered better and safer than synthetic insecticides; they must be toxic to the target organism, yet with low or no toxicity to non-target organisms. Many plant extracts have seen their high insecticide potential confirmed under laboratory conditions, and in the search for plant compounds with bioinsecticidal activity, the Lamiaceae family has yielded satisfactory results. Objective: The aim of our study was to develop computer-assisted predictions for compounds with known insecticidal activity against Aphis gossypii and Drosophila melanogaster. Results and conclusion: Structure analysis revealed ent-kaurane, kaurene, and clerodane diterpenes as the most active, showing excellent results. We also found that the interactions formed by these compounds were more stable, or presented similar stability to the commercialized insecticides tested. Overall, we concluded that the compounds bistenuifolin L (1836) and bistenuifolin K (1931), were potentially active against A. gossypii enzymes; and salvisplendin C (1086) and salvixalapadiene (1195), are potentially active against D. melanogaster. We observed and highlight that the diterpenes bistenuifolin L (1836), bistenuifolin K (1931), salvisplendin C (1086), and salvixalapadiene (1195), present a high probability of activity and low toxicity against the species studied.