Estimativa de mortalidade de Spodoptera frugiperda alimentadas com milho Bt (2B655PW) em ambiente semiárido.

Abstract

Corn Bt is widely used in crops on Southeast- Mid West belt for control of several Lepidoptera, among them fall armyworm (Spodoptera frugiperda). This technology has been adopted worldwide for more than 20 years, however, with continuous use reports of resistance breakdown have been recorded as a function of insect selection pressure. Monitoring and pursuing strategies to delay this process ensure the sustainability of this technology. In order to evaluate the toxicity of Corn Bt (2B655PW) in a semi-arid environment, mortality of fall armyworm larvae was estimated using leaves collected in four growth stages. Seeds of Bt and conventional were cultivated in the field during final of rainy season. Leaves were collected at 40, 55, 70 and 85 days after emergence and used to feeding assays, using larvae in cage (24-well plates) and subsequently maintained in BOD (25 ± 2 ° C) for 5 days. The rate of mortality was 100% in larvae fed on 40 dae-leaves. With the course of the crop cycle, there was a low reduction reaching a value of 92.8% at 85 dae. This indicates that this technology is promising in controlling S. frugiperda under semi-arid conditions. However, considering the infestation of insects in extensive areas, it is necessary constant monitoring in the field in order to detect possible emergence of resistant insects that could accelerate the fall in efficiency of the cultivar.