INFLUÊNCIA DE SISTEMAS DE MANEJO DE SOLOS E DE CULTURAS SOBRE INSETOS SUBTERRÂNEOS

Portuguese. RESUMO Avaliou-se a influência de sistemas de manejo de solos e de culturas sobre insetos subterrâneos, em Cruz Alta, RS, de fevereiro de 1987 a agosto de 1990. Amostras de solo foram coletadas mensalmente e os insetos separados e identificados. Observou-se maior número de insetos no sistema de plantio direto (SMPD), com 62,0% do total. Larvas de elaterídeos, Acrolophus sp., Diloboderus abderus e Pantomorus sp., além de adultos de Ataenius sp., Blapstinus punctulatus e Cyrtomenus mirabilis, ocorreram com maior freqüência no SMPD, enquanto que larvas de Diabrotica speciosa e Elasmopalpus lignosellus foram mais freqüentes no sistema de plantio convencional (SMC). Notou-se maior número de insetos no sistema de manejo cultural soja-soja-milho do que soja contínua, com 58,7% do total, e trigo-aveia-ervilhaca em relação a trigo contínuo e trigo-aveia, com 35,9%, devido ao elevado percentual de freqüência de larvas de Diabrotica speciosa nestes dois sistemas de culturas.

English. SUMMARY The influence of soil and crop management systems on underground insects was evaluated, in Cruz Alta, Brazil, from February 1987 to August 1990. Soil samples were collected monthly and insects were separated and indentified. A greater number of insects was observed in no-till sowing system (MT), with 62.0% of the total. Larvae of elaterids, Acrolophus sp., Diloboderus abderus and Pantomorus Sp., as well as adults of Ataenius sp., Blapstinus punctulatus and Cyrtomenus mirabilis, showed a higher ocurrence frequency in the NT, while larvae of Diabrotica speciosa and Elasmopalpus lignosellus was more frequent in the conventional-tillage system (CT). A greater number of insects was found in the soybean-soybean-corn crop management, with 58.7% of the total, when compared to soybean grown continuously, and wheat-oat-vetch crop management, with 35.9%, when compared to wheat grown continuously and in wheat-oat, due to the high frequency of Diabrotica speciosa larvae in these systems.