EFFECTIVENESS OF TRANSGENIC BT MAIZE TO CONTROL Helicoverpa armigera (LEPIDOPTERA: NOCTUIDAE)

The caterpillar Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae), identified in Brazil in 2013, greatly worries farmers because of its destructive power. The technology of transgenic plants that induces resistance to insects is a great ally for controlling caterpillars. In this study we compared the performance of transgenic Bt maize in the controlling of different larval instars of H. armigera in semi-field seedlings. There were tested the following genotypes: (1) Non-Bt maize Iso-hybrid (Control); (2) Cry1F; (3) Cry1F+ Cry1A.105 + Cry2Ab2; (4) Cry1A.105 + Cry2Ab2; (5) Cry1Ab + Cry1F; (6) Cry1Ab + Vip3Aa20. The experimental design was organized in randomized blocks with eight replications, each consisting of a pot with 5 plants artificially infested with larvae of 2nd, 3rd or 4th instar. At 1, 3, 7, 10 and 14 days after infestation, plants were evaluated for defoliation. In the 3rd instar larvae bioassay, there was high predation by birds, but until seven days after infestation all transgenic maize were efficient to the pest. All transgenic Bt maize were effective in the control of tested H. armigera larvae instars.