CONTROLE DAS LAGARTAS Spodoptera frugiperda E Pseudaletia sequax EM MILHO PELA ASSOCIAÇÃO DE HÍBRIDOS Bt, INTERVALO DE DESSECAÇÃO E INSETICIDAS

Abstract

Bt corn is characterized as a technology for pest management that has been used in Brazil since the 2008/2009 season. Bt corn hybrids currently available on the market resulted from five transgenic events for the control of caterpillars, MON 810, Bt11, TC 1507, MON 89034, and MIR 162, which express Cry1Ab, Cry1Ab, Cry1F, Cry1A.105 + Cry2Ab2, and Vip3A toxins, respectively. The increased adoption of no-tillage farming has a major influence on insect pests, including caterpillars. Black oat is the main winter cover crop preceding soybeans and corn crops in the summer, and it is grown in large areas in the states of Rio Grande do Sul, Santa Catarina, and Paraná.Direct sowing of maize on desiccated black oat may favor the occurrence of insects with potential for damage, especially during germination and seedling stage. Therefore, the aim of this study was to evaluate the effectiveness of Bt corn associated with the following management practices: a) interval between black oat desiccation and maize sowing, with and without application of the insecticide lufenurom; b) seed treatment with the insecticides thiamethoxan + fipronil and thiodicarb + imidacloprid to reduce the damage caused by Pseudaletia sequax and Spodoptera frugiperda caterpillars in the beginning of the development of corn plants.Four experiments were conducted under field conditions and no-tillage farming on desiccated black oat, two with natural infestation of insect pests and two with artificial infestation of S. frugiperda using cages. The four experiments were conducted in Itaberá, SP during the seasons 2009/2010 and 2010/2011. The 40-day interval between black oat desiccation and maize sowing proved to be effective in reducing damage caused by P. sequax in Bt corn 30F53H (Cry1F), regardless of insecticide application for desiccation or seed treatment. When black oat desiccation was carried out 15 days before maize sowing, a higher occurrence of damage caused by P.sequax in 30F53H Bt corn was observed. In this case, the seed treatment with thiodicarb + imidacloprid proved to be more effective in reducing damage. Corn hybrid 30F53H was effective in reducing damage caused by S. frugiperda, regardless of desiccation interval or use of insecticides. Corn hybrids DKB 240YG (Cry1Ab),DKB 240H (Cry1F), 30F53H (Cry1F), DKB 390PRO (Cry1A.105 + Cry2Ab2), and Garra Viptera (Vip3A) were effective in reducing the number of plants cut by S. frugiperda third instar caterpillars compared with non-Bt corn, regardless of the seed treatment used. Corn hybrids DKB 240H, DKB 390PRO, and Garra Viptera were effective in reducing damage caused by S. frugiperda, such as scraped plants and damaged whorls, compared with non-Bt corn, regardless of the seed treatment used. Corn hybrid DKB 240YG presented reduction in damaged whorls only when associated with seed treatment with the insecticide thiodicarb + imidacloprid. The use of Bt corn with other management practices significantly contributed to reduction of damage caused by P. sequax and S. frugiperda in the beginning of the development of the crop. Therefore, the use of Bt corn should be considered as one more practice in corn integrated pest management.