Desempenho do algodão Bt no controle de Helicoverpa armigera (Hübner, 1808) (Lepidoptera: Noctuidae) e Spodoptera frugiperda (Smith, 1797) (Lepidoptera: Noctuidae) e a competição interespecífica destes lepidópteros

Abstract

The cotton plant is a host of a pest complex that can cause damage to all its structures. Among these pests, Helicoverpa armigera and Spodoptera frugiperda species are present in many producing regions of the Brazilian cerrado. Through Biotechnology, a new tatic for pest control was developed: the genes of Bacillus thuringiensis (Bt) have been introduced into cotton plants, yielding genetically modified cotton, conferring resistance to the attack of certain Lepidoptera species. The aim of this study was to evaluate the crawler mortality of H. armigera and S. frugiperda when both were fed with Bt and non-Bt cotton, as well as to evaluate the interspecific competitive behavior between H. armigera and S. frugiperda when exposed to non-Bt cotton . The experiments were conducted at the Agricultural Entomology Laboratory of the University Federal da Grande Dourados, Dourados (MS). The tested cotton plants were: FM - 982 GL® (non-Bt), DP 555BGRR® (Cry1Ac), FM 975WS® (Cry1Ac + Cry1F), DP 1228B2RF® (Cry1Ac + Cry2Ab2) and FM 940GLT® (Cry1Ab + Cry2Ae). The larvae mortality studies of H. armigera and S. frugiperda were performed in the laboratory and interspecies competition study of H. armigera and S. frugiperda were carried out in the field. The experimental design for mortality studies was randomized (CRD) with five treatments and 10 repetitions. On the other hand, the study of interspecific competition was block randomized with fifteen treatments and four replications. We observed that the Bt cotton varieties DP 1228B2RF® and FM 940GLT® caused mortality to H. armigera when fed with leaves and all varieties of Bt cotton showed a high mortality of H. armigera when fed reproductive structures. In S. frugiperda mortality study, the variety FM 975WS® showed high mortality when fed with leaves and also when fed with reproductive structures. In the competition study the predominant species was the H. amigera.