Impact of deltamethrin on arthropods in maize under conventional and no-tillage cultivation

Insecticides are frequently applied to tropical maize crops, but little is known about their impact on the associated arthropod assemblage. The response of the arthropod assemblage to deltamethrin application was assessed in three maize fields subjected to either conventional or no-tillage cultivation, with or without deltamethrin application. Arthropods were sampled before and after insecticide application. There was a significant effect of the cultivation system on the arthropod assemblage. The no-tillage cultivation system was able to buffer the impact of the insecticide on the arthropod assemblage, minimizing its effect. This did not occur in the conventional cultivation system where deltamethrin significantly decreased arthropod abundance in the maize canopy. Among the 23 taxa collected, the herbivore species Spodoptera frugiperda (Lepidoptera: Noctuidae), Dalbulus maidis (Homoptera: Cicadellidae) and Diabrotica speciosa (Coleoptera: Chrysomelidae), and the predators Orius sp. (Heteroptera: Anthocoridae), Doru luteipes (Dermaptera: Forficulidae) and Cycloneda sanguinea (Coleoptera: Coccinellidae) were the main contributors to the existing variance. Among these six species, only D. speciosa showed negligible contribution to the divergence among treatments. There was significant correlation between herbivores and predators; for example, the earwig D. luteipes showed a significant negative correlation with S. frugiperda and D. maidis. (C) 2004 Elsevier Ltd. All rights reserved.