Performance of Bt Maize Hybrids Against Spodoptera frugiperda (Lepidoptera: Noctuidae) in a Tropical Ecotone

The fall armyworm, Spodoptera frugiperda J.E. Smith (Lepidoptera: Noctuidae) is a major pest of maize, responsible for significant productivity losses worldwide. A widely adopted control strategy involves genetically modified maize cultivars expressing Bacillus thuringiensis (Bt) genes, which produce toxic proteins such as Cry and Vip3Aa. Despite its effectiveness, the continuous use of Bt technology necessitates rigorous evaluation due to the potential development of genetic resistance, which can lead to control failures. This study evaluated and compared the susceptibility of S. frugiperda to Bt proteins under field conditions using two Bt maize cultivars (NK 555 VIP3 and DKB 390PRO4) and two conventional cultivars (DKB 3800RR and P3889 R) in a randomized block design over two cropping seasons (2022 and 2023). Results demonstrated high efficacy of Bt maize hybrids, with no significant foliar damage observed in Bt cultivars. In contrast, conventional cultivars exhibited larval infestations as early as 29 days after sowing (DAS), leading to moderate foliar damage. These findings confirm the effectiveness of Bt technology in managing S. frugiperda populations while underscoring the need for continuous field monitoring to address the risk of resistance evolution, which could compromise the long-term success of these strategies in the study region.