The fall armyworm (FAW), Spodoptera frugiperda, is a highly destructive pest in agriculture. Broflanilide, specifically designed to target the GABA receptors in insects, is effective against various Lepidoptera pests, including FAW. However, the patterns of cross-resistance between broflanilide and other insecticides, especially the underlying molecular mechanisms behind cross-resistance, remain unclear. In this study, a broflanilide-resistant strain of S. frugiperda (F24) was established after 24 generations of continuous selection in the laboratory with a resistance ratio of 4.04-fold. The cross-resistance ratio of broflanilide was found to be 2.95-fold for lambda-cyhalothrin and 2.82-fold for cyproflanilide in the F24 generation. Additionally, an apparent antagonistic effect was observed when broflanilide was mixed with a lambda-cyhalothrin mixture at all volume ratios. Moreover, qPCR combined with CRISPR-Cas9 showed that the gene SfCYP6B42 partially contributed to the cross-resistance between broflanilide and lambda-cyhalothrin, which first elucidated the cross-resistance mechanism between broflanilide and lambda-cyhalothrin.
Zhen et al. (Mon,) studied this question.