Effects of no-tillage and of soybean-corn intercropping on natural enemies and pests

Abstract

This study evaluated the effects of no-tillage and of strip intercropping of soybean (Glycine max (L.) Merrill) and corn (Zea mays L.) on the abundance of pests and natural enemies. The plots were arranged in a randomized complete block design for a 3 x 2 factorial experiment (soybean monoculture, corn monoculture, strip intercropping of soybean-corn x no-tillage and conventional tillage). Insects were sampled by sweep net, ground cloth, visual search and suction net. Among the corn insect pests, Maecolaspis assimilis occurred in highest number in the no-tillage system, the same being observed with the predators Cycloneda sanguinea and Doru sp. On the other hand, M. assimilis and the predator Toxomerus sp. were more abundant in corn monoculture than in corn of the strip-intercropping system. Considering the soybean insect pests, highest number of Anticarsia gemmatalis and Diabrotica gracilenta was found in the conventional tillage system; the same happened to the Trichogrammatidae species, while species of Eulophidae family were more numerous in soybean under no-tillage system. Soybean of the strip-intercropping system showed highest abundance of the insect pests Megalotomus sp. and Maecolaspis sp. and the natural enemies Geocoris sp., Lebia concina, Oriussp., Braconidae and Scelionidae.