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.
A lagarta Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) chegou ao Brasil em 2012 e vem causando prejuízos severos aos agricultores, especialmente nas culturas do algodão, feijão, milho, soja e tomate nas regiões Norte, Nordeste e Centro-Oeste. Pouco se conhece sobre seus danos às culturas no país e o feijoeiro é uma das culturas menos estudadas dentre as citadas. Portanto, esse trabalho objetivou-se avaliar o nível de dano causado pela lagarta H. armigera de 3º ínstar em plântulas de feijão cv. BRS-Estilo. O ensaio foi semeado em 10/04/2014, em Ribeirão Preto, SP, com espaçamento de 0,5 m e 12 plantas por metro. Em um delineamento em blocos casualizados, as infestações (18/04) de 0 (testemunha), 0,1, 0,2, 0,5 e 1 lagarta por planta foram repetidas quatro vezes, em parcelas de 0,5 m2 cercadas por barreias de PVC de 20 cm de altura e com bordadura de 1 m. Após 1, 3, 7 e 14 dias após a infestação foi avaliada a porcentagem de desfolha. A porcentagem média de desfolha foi proporcional à densidade de lagartas. O nível de dano de lagartas de 3º ínstar de H. armigera é de 1,4 lagartas por planta e, dessa forma, o nível de controle deve ser de 0,7 lagartas por planta de feijoeiro.
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