Imidacloprid affects the functional response of predator Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) to strains of Spodoptera frugiperda (J.E. Smith) on Bt cotton.

Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) is one of the most common asopine species in the neotropical region and its occurrence was reported in several countries of South and Central America, as an important biological control agent for many crops. This study was carried out to identify the imidacloprid impacts on the functional response of predator P. nigrispinus fed on Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) strain resistant to lambda-cyhalothrin, on Bt cotton expressing Cry1Ac (Bollgard(®)). Spodoptera frugiperda larvae were used in the following conditions: resistant (1) and susceptible (2) strains to lambda-cyhalothrin fed on Bollgard(®) cotton leaves (DP 404 BG); and resistant (3) and susceptible (4) strains to lambda-cyhalothrin fed on non-genetically modified cotton leaves (cultivar DP4049). The predatory behavior of P. nigrispinus was affected by imidacloprid and the type II asymptotic curve was the one that best described the functional response data. Handling time (T h ) of predator females did not differ among treatments in the presence of imidacloprid. The attack rate did decrease, however, due to an increase in the density of larvae offered. Regardless of the treatment (S. frugiperda strain or cotton cultivar), the predation of P. nigrispinus females on S. frugiperda larvae was significantly lower when exposed to imidacloprid, especially at a density of 16 larvae/predator. The predation behavior of P. nigrispinus on S. frugiperda larvae is affected by the insecticide imidacloprid showing that its applications should be used in cotton crop with caution.