INTERACTION BETWEEN TRANSGENICS AND INSECTICIDES IN THE CONTROL OF KEY PESTS ON OFF-SEASON MAIZE HYBRIDS

ABSTRACT Diverse lepidopteran pests attack the maize crop. The commercialization of hybrids of transgenic Bt maize, integrating in its genome the gene Cry1Ab, from Bacillus thuringiensis subsp. kurstaki, which codifies the protein with toxic effect on insects of the Lepidoptera order, has been recently introduced in Brazil. The objective of this work was to evaluate, under field conditions, the effectiveness of conventional and transgenic maize hybrids for the control of pests, sprayed or not with insecticides. The assay was carried out in an experimental area of the Polo Apta Centro Norte, in Pindorama, São Paulo State, Brazil. Five conventional maize hybrids were evaluated in comparison with the respective isogenic Bt hybrids. The evaluation was carried out every 10 days, in 20 plants of the 2 central lines of the parcel for Spodoptera frugiperda (Smith) damage. For damages of Helicoverpa zea (Bod.) and Diatraea saccharalis (Fab.) the evaluations were carried out in the pre-harvest. The interactions between the hybrids and the transgeny occurred in all evaluations starting at the 40th day after emergence (DAE). The Bt hybrids evaluated presented the lowest scores for visual S. frugiperda damages in all the evaluations. The transgenic maize also provided the lowest percentage of cobs damaged by H. zea and S. frugiperda, and of stalks attacked by D. saccharalis. In conclusion, the transgenic maize provided reduction in visual damages caused by the pests, however, it presented different performance among the hybrids.