Differential susceptibility of Spodoptera frugiperda (Lepidoptera: Noctuidae) to single versus pyramided Bt traits in Brazilian soybean: what doesn't kill you makes you stronger?

BACKGROUND Lepidopteran pest control in agriculture has become heavily dependent on cultivars that express Bacillus thuringiensis (Bt) toxins as ‘plant‐incorporated protectants’. However, populations of Spodoptera frugiperda (Smith) in Brazil appear resistant to the Bt traits currently available in commercial soybean cultivars. RESULTS This study evaluated S. frugiperda life history when feeding on three different Bt soybean cultivars. Cultivars expressing Cry1Ac + Cry1F and Cry1A.105 + Cry2Ab2 + Cry1Ac Bt toxins caused 100% larval mortality in S. frugiperda. Both non‐Bt and Cry1Ac‐expressing soybean induced transgenerational effects that increased the survival of subsequent generations. A Cry1Ac soybean diet reduced the generation time (T) of S. frugiperda relative to non‐Bt soybean, resulting in shorter generation time and more rapid population growth. CONCLUSION The implications of these results revealed how diet can alter aspects of insect life history and biology, and have important implications for sustainable management of S. frugiperda on soybean. © 2024 Society of Chemical Industry. Field populations of fall armyworm in Brazil are evolving resistance to Bt soybean cultivars. Cry1Ac soybean shortened FAW generation time and accelerated population growth.