Genetically modified crops that produce insecticidal proteins from Bacillus thuringiensis (Bt) are currently the most efficient and safest method of pest control worldwide. However, the prolonged planting period has led to a reduction in the efficacy of Bt crops due to the evolution of pest resistance in the field. This review paper examines the resistance status of lepidopteran pests to Bt crops under field conditions, elucidates the molecular mechanism underlying their resistance to Bt Cry toxins, and discusses resistance management strategies based on these mechanisms. Extensive research has demonstrated that mutations and alterations in expression patterns of midgut receptor genes are closely associated with Bt resistance. As our understanding of molecular mechanisms progresses, several innovative approaches such as DNA molecular detection techniques, engineering modified Cry toxins, and combining Bt toxin with RNAi technology have been developed for effective pest control measures. Future research will further unravel the intricate molecular mechanisms underlying this phenomenon to develop scientifically sound integrated pest management strategies.

Hippodamia variegata is a key natural enemy of various aphid pests in agricultural ecosystems, and its foraging and oviposition behaviors are strongly dependent on chemical signals from prey aphids and host plants. In this study, we functionally characterized the chemosensory protein HvarCSP8 to elucidate its potential role in mediating olfactory responses to aphid-induced plant volatiles. The expression profiles of HvarCSP8 were examined by quantitative real-time PCR (qRT-PCR) across developmental stages and sexes; the recombinant HvarCSP8 was purified; the potential ligands specificity and affinity were studied using fluorescence-based competitive binding assays; and structural characteristics were obtained via homology modeling and molecular docking simulations. The results demonstrated that HvarCSP8 exhibits pronounced sex- and tissue-specific expression, with significant upregulation in adult antennae, particularly in females. The purified protein exhibited selective binding affinity to multiple aphid-induced plant volatiles, such as α-Farnesene, α-Terpinene, and 2-Ethyl-1-hexanol. Molecular docking revealed that HvarCSP8 interacts with these ligands through multiple amino acid binding sites, among which hydrophobic residues such as VAL29, LEU61, ILE64, and LEU65 frequently occur in binding sites for multiple ligands, suggesting that these residues play important roles in binding. These findings indicate that HvarCSP8 may be involved in the olfactory detection of aphid-induced plant volatiles in H. variegata, providing a candidate target for the development of behavior-based biological control strategies against aphid pests.