Efeito de toxinas do milho Bt sobre a patogenicidade e a reprodução de nematoides entomopatogênicos (Rhabditida: Steinernematidae, Heterorhabditidae) em larvas de Spodoptera frugiperda (Lepidoptera, Noctuidae)

Abstract

The use of genetically modified plants expressing proteins with insecticidal action has been an important tool in controlling Spodoptera frugiperda (JE Smith), a major corn (Zea mays L.) pest. The continuous and inadequate use of this technology has reduced the degree of population suppression of caterpillars and, knowing that fitness costs may delay pest resistance in crops producing insecticidal toxins derived from Bt, new strategies have been addressed. The entomopathogenic nematodes (EPN) have symbiosis with bacteria and are important agents of biological control for several insects, and can be an alternative and safe method for the control of pests. Although some studies have shown the combined use of Bt corn and EPN for control of S. frugiperda, little is known about the effect of Bt on EPN. In this context, to identify the effect of Bt on EPN used to control S. frugiperda populations resistant to Cry1A.105, Cry2Ab2 and Cry1F proteins, 1mL of suspension containing 500 infective juveniles (IJ) / ml of Heterorhabditis amazonensis isolate JPM4, Heterorhabditis amazonensis isolate RSC05 and Steinernema carpocapsae, were applied in caterpillars resistant to these proteins 15 days after hatching, fed only by Bt corn, in order to evaluate the effects of the pathogenicity of EPN. The pathogenicity of these isolates to Bt resistant populations of S. frugiperda and the reproductive capacity of these NEP by these populations were evaluated. Finally, the pathogenicity of the subsequent generation of EPN was evaluated using last instar G. mellonella larvae as hosts. H. amazonensis isolate RSC05 had its pathogenicity, reproductive capacity and pathogenicity of the subsequent generation affected. For H. amazonensis isolate JPM4 only pathogenicity of the subsequent generation IJ was affected when produced by the resistant population to Cry1F. S. carpocapsae did not have any of the parameters affected by the presence of Cry proteins.