Ação de inimigos naturais em presas sentinelas no agrossistema algodoeiro em função do inseticida recomendado

Abstract

Cotton ecosystem in Brazil hosts an array species of herbivores. Some of these regularly reach population densities requiring curative control decisions. Nonethless, a large diversity of natural is associated with these herbivores and brings contribution to the integrated pest management (IPM). To furnish the cotton IPM is recommended the use of selective insecticides, but few data show how this decision bring benefits relative to the action of conserved natural enemies. Thus, the impact of recommending selective and non-selective insecticides against cotton pests on the action of naturally occurring natural enemies was measured: (i) using sentinel prey set up in the field; and (ii) impact of dried residues of field recommended insecticides on survival of four key predatory insects representing different feeding habits and prey attacked (Chrysoperla externa, Eriopis connexa, Orius insidiosus and Podisus nigrispinus). The mortality of the sentinel prey itens was higher in the field under selective recommendation relative to the non-selective, and most of time, similar to the untreated fields. Further, non-selective insecticides maintained the impact between spray decisions depending on the insecticide recommended and time between sprays. Seasonal abundance of predatory insects from cotton plants was 2x greater in the fields under selective and non-spray decisions, despite the variation observed across the 15 weeks surveyed. The survival of assayed predators exposed to the dried insecticide residues within the intervals 0, 5, 10 and 15 days after spray supports the field outcome. The selective insecticides pymetrozin, chlorantraniliprole, pyripoxifen and cyantraniliprole promoted greater predator survival relative to the non-selectives lambda-cyhalothrin, malathion, dimethoate and thiamethoxam. In general, among the non-selective insecticides, malathion and dimethoate exhibited shorter residual compared to the thiamethoxam and lambda+thiamethoxam. Therefore, we can conclude that the recommendation of selective insecticides brings benefits for cotton IPM by conserving the action of the natural enemy community in the local.