Understanding genetic variability in some Lepidopteran pests to manage insecticide and Bt resistance in different cropping systems in Brazil

Annual cropping systems are very diverse and complex in Brazilian agriculture. Understanding the spatial and temporal variability of diverse crops in major agricultural ecosystems is crucial for designing a reliable pest management program. Transgenic insecticidal cultivars, such as Bt cotton and maize, became part of the cropping systems in Brazil only in the past 5 years. Because of successive plantings of some crops such as maize, cotton and soybeans in some Brazilian regions, problem of insecticide resistance is very common in some major insect pests. Resistance monitoring of Spodoptera frugiperda populations to major groups of insecticides (pyrethroid, organophosphate, chitin synthesis inhibitor and naturalyte) was conducted in different Brazilian cropping systems. Genetic structure of populations of S. frugiperda, Heliothis virescens and Diatraea saccharalis under different cropping systems was determined with molecular markers. Implications of the results for resistance management strategies will be discussed.