Dynamics of Spodoptera frugiperda in Bt and non-Bt maize hybrids semi-arid ecotone of northeastern Brazil
ABSTRACT The fall armyworm (Spodoptera frugiperda; Lepidoptera: Noctuidae) is a major maize pest that causes substantial yield losses worldwide. A widely adopted management strategy involves genetically modified maize hybrids that express Bacillus thuringiensis (Bt) genes and produce insecticidal proteins such as Cry and Vip3Aa. However, the long-term sustainability of Bt technology depends on continuous field monitoring, particularly in regions characterized by high temperatures and seasonal drought. This study evaluated the field incidence, infestation levels, and foliar damage caused by S. frugiperda in Bt and non-Bt maize hybrids. Two Bt hybrids (NK 555 VIP3 and DKB 390PRO4) were compared with two non-Bt hybrids (DKB 3800RR and P3889 R) in a randomized block design conducted over two consecutive cropping seasons (2022 and 2023) under semi-arid conditions in Northeastern Brazil. Across both cropping seasons, no larvae or significant leaf damage were recorded in the Bt hybrids, whereas the non-Bt hybrids exhibited larval infestations beginning at 29 days after sowing (DAS), which led to moderate leaf damage levels. Infestation peaks occurred between 30 and 70 DAS and demonstrated consistent seasonal patterns in non-Bt hybrids. These findings demonstrate the stability of field performance of pyramided Bt hybrids against S. frugiperda under semi-arid ecotone conditions and reinforce the importance of regional surveillance programs to support insect resistance management strategies and sustain Bt technology in maize production systems.