Comparison of bt transgenic maize in control of Elasmopalpus lignosellus in the field

Resumo

The Lepidoptera insects are responsible for large losses in maize production in Brazil, and stand out those that attack seedlings, such as lesser cornstalk borer, Elasmopalpus lignosellus (Zeller). The objective of this work was to compare the performance of transgenic Bt maize in the control of the E. lignosellus caterpillar in the maize seedlings phase in two trials. In the first trial six treatments were tested: (1) Conventional Non-Bt maize; (2) Conventional Non-Bt maize with insecticide application; (3) transgenic maize expressing the Cry1Ab genes; (4) Cry1F; (5) Cry1A.105 + Cry2Ab2; (6) Cry1A.105 + Cry2Ab2 + Cry1F. The experimental design was randomized blocks, where each treatment was repeated 4 times in plots of 22.5 m2. Ten consecutive plants with third instar larvae of E. lignosellus in the seedling stage were artificially infested. Only the Non-Bt  maize (Control) was affected by the E. lignosellus caterpillar, but all the treatments presented tillering, galleries and holes in the stem. In the second assay the genotypes used were seeded on 11/23/2012, and the damages of 3rd instar caterpillars of E. ligosellus (Zeller) were evaluated. The treatments were: (1) Conventional Non-Bt maize (Control); (2) transgenic maize expressing the Cry1F + Cry1A.105 + Cry2Ab2 genes; (3) Cry1A.105 + Cry2Ab2; (4) Vip3Aa20; (5) Vip3Aa20 + Cry1Ab; (6) Cry1F; (7) Cry1Ab + Cry1F. The plots were formed by a line spaced in 0.7 m of 2 m, with 10 plants, with barriers to prevent the exit of artificially infested insects. In the first and second assays, non-Bt maize with or without insecticide application were affected by E. lignosellus caterpillars. However, Bt transgenic maize was not harmed by E. lignosellus caterpillars, except the Vip3Aa20 treatment. Bt transgenic plants were poorly damaged by E. lignosellus in the seedling and leaf stage.