The harlequin ladybird, Harmonia axyridis Pallas (Coleoptera: Coccinellidae), is a generalist predator and an effective biocontrol agent of various insect pests that has been exploited for the control of aphid pests in the greenhouse and field. However, insecticides are widely used to control aphid pests worldwide and the potential non-target effects of sulfoxaflor and imidacloprid for controlling aphid pests towards this biocontrol agent are little known. Although both sulfoxaflor and imidacloprid act on nicotinic acetylcholine receptors of insects, sulfoxaflor has a novel chemical structure compared with neonicotinoids. We assessed the lethal, sublethal and transgenerational effects of sulfoxaflor and imidacloprid on H. axyridis simultaneously exposed via ingestion of contaminated prey and via residual contact on the host plant at LC₂₀ and LC₅₀ doses estimated for the cotton aphid. Imidacloprid significantly reduced the survival of H. axyridis adults compared to sulfoxaflor at the same lethal concentration against cotton aphid. Both concentrations of imidacloprid and sulfoxaflor reduced the proportion of ovipositing females, and both concentrations of imidacloprid and sulfoxaflor, except LC₂₀ dose of sulfoxaflor, reduced the fecundity and fertility of the parental generation. In the progeny of imidacloprid- and sulfoxaflor-exposed parents, both tested LC₅₀ concentrations significantly decreased the juvenile survival rate, and both concentrations of imidacloprid and sulfoxaflor, except LC₂₀ dose of sulfoxaflor, prolonged the development time. Our findings provide evidence of the negative influence of imidacloprid and sulfoxaflor at low lethal concentrations on the harlequin ladybird and on the progeny of exposed individuals, i.e., transgenerational effects. Hence, these findings stress the importance of optimizing the applications of imidacloprid and sulfoxaflor for the control of aphid pests, aiming at preserving the biocontrol services provided by H. axyridis throughout the integrated pest management approach.

Trehalose is an important carbohydrate substance in insect hemolymph. Chitin is the main component of cuticle and peritrophic matrix in insects. Trehalase (Tre) catalyzes the decomposition of trehalose. Few studies of trehalase in lepidopteran insects have been conducted. Here, the functions of soluble Tre (Tre1) and membrane-bound Tre (Tre2) in the growth and development of Mythimna separata were investigated. We cloned and identified Tre1 and Tre2 cDNA sequences in M. separata. Analysis expression revealed that MsTre1 and MsTre2 were highly expressed in midgut and integument, respectively. The expression of MsTre1 and MsTre2 was highest in the pupal stage. We used RNA interference (RNAi) to inhibit Tre expression in M. separata larvae. Injection of dsMsTre1 or dsMsTre2 resulted in abnormal phenotypes and impeded normal molting. Silencing of MsTre1 and MsTre2 resulted in significant changes in the expression of genes in the trehalose and chitin metabolism pathways, significantly increased the trehalose and glycogen content, and significantly decreased MsTre1 and MsTre2 activity, the glucose content, and the chitin content in midgut and integument. Silencing of MsTre1 slowed larval molting, and the new cuticle was significantly thinner. These results indicate that RNAi of Tre may be useful for control strategies against M. separata.

Soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is a major pest of soybean fields. While high-temperature stress induced by global warming can initially suppress aphid populations, these pests may eventually adapt, leading to more severe infestations and crop damage. Heat shock proteins (HSPs), which are upregulated in response to heat stress to protect aphid development, also confer tolerance to other abiotic stressors, including insecticides. To investigate the role of HSPs in insecticide resistance in A. glycines, we analyzed the expression profiles of three AgHsp90 genes (AgHsp75, AgHsp83, and AgGrp94) following exposure to high temperatures and insecticides. Functional validation was performed using RNA interference (RNAi) to silence AgHsp90 genes. Our results demonstrated that AgHsp90 genes were significantly upregulated under both heat and insecticide stress conditions. Furthermore, after feeding on dsRNA of AgHsp90 genes, mortality rates of A. glycines significantly increased when exposed to imidacloprid and lambda-cyhalothrin. This study provides evidence that AgHsp90 genes play a crucial role in mediating thermal tolerance and insecticide resistance in A. glycines.

Hippodamia variegata (Coleoptera: Coccinellidae) is an important predator of the cotton aphid, Aphis gossypii, and it plays an important role in its biological control. However, widespread use of neonicotinoid insecticides such as imidacloprid may exert sublethal effects on non-target natural enemies. In this study, we evaluated the impact of sublethal imidacloprid exposure on the olfactory behavior of H. variegata and explored the underlying molecular mechanisms. Adult beetles were fed cotton aphids treated with imidacloprid at 3.93 mg a.i./L (LC₂₀) and 13.62 mg a.i./L (LC₅₀), and their olfactory responses to aphid-infested versus uninfested cotton leaves were assessed using a Y-tube olfactometer. In parallel, transcriptomic profiling was conducted on the antennae and brain tissues of adult male and female beetles from both control and treatment groups, followed by GO/KEGG enrichment analyses and qRT-PCR validation of candidate genes. Finally, RNA interference (RNAi) was used to functionally verify the roles of selected odorant-binding protein (OBP) genes in the sublethal effects observed. Y-tube assays showed that control adults exhibited significant attraction to aphid-infested cotton plants, whereas beetles of both sexes exposed to LC₂₀ and LC₅₀ imidacloprid lost this olfactory preference. Transcriptomic analyses revealed extensive differential gene expression in the antennae and brains of beetles treated with LC₂₀ and LC₅₀ compared with the control group, with differentially expressed genes significantly enriched in pathways associated with metabolic processes, ribosomes, RNA transport, and neural signaling. Notably, several olfaction and neural function-related genes, including Obp2, Obp7, Obp8, Obp10, Ten-m, and Nlg4, were significantly downregulated after imidacloprid exposure, and these patterns were confirmed by qRT-PCR. RNAi-mediated silencing of Obp2, Obp7, Obp8, and Obp10, which significantly reduced transcript levels and eliminated the olfactory preference for aphid-infested cotton plants in behavioral assays, supporting their essential roles in prey-related odor perception. Overall, our findings demonstrate that sublethal imidacloprid exposure impaired olfactory function in H. variegata and was associated with transcriptional disruptions in olfactory and neural signaling pathways, which may compromise its efficiency as a biological control agent. These results highlight the need to consider sublethal ecological risks of insecticide use and to optimize pesticide application strategies to better align with integrated pest management programs.

Common ragweed, Ambrosia artemisiifolia L., a noxious invasive plant, produces novel secondary metabolites. However, it attracts soybean aphid, Aphis glycines, a significant pest of soybean, to feed on it. Elucidating the molecular mechanisms of A. glycines adaptation to A. artemisiifolia may help identify target genes useful for pest management. High-throughput transcriptome sequencing identified 4250 differentially expressed genes (DEGs), with 2399 upregulated and 1851 downregulated. KEGG pathway enrichment analysis suggested that these DEGs were significantly involved in core detoxification-related pathways, including metabolism of xenobiotics by cytochrome P450, drug metabolism, ascorbate and aldarate metabolism, and pentose and glucuronate interconversions. Further analysis revealed significant upregulation of 17 UDP-glycosyltransferase (UGT) genes, with AgUGT342B2, AgUGT343B2, AgUGT344J2, AgUGT344L2, and AgUGT344N2 showing 6.34-, 6.22-, 2.14-, 3.98-, and 7.49-fold higher expression, respectively, than in A. glycines fed on soybean. Bioassays demonstrated that A. glycines reared on A. artemisiifolia exhibited significantly reduced sensitivity to three common insecticides, imidacloprid, thiamethoxam, and lambda-cyhalothrin, with LC₅₀ values increasing by 5.8-fold, 2.8-fold, and 3.6-foldhigher, respectively, than those reared on soybean. These findings indicate that feeding on A. artemisiifolia induces UGT gene family upregulation in A. glycines, conferring cross-resistance to multiple insecticide classes. This study reveals a molecular mechanism linking host adaptation to insecticide resistance, highlighting the ecological and evolutionary consequences of invasive plant-herbivore interactions.