Efeitos de inseticidas sobre a mortalidade e biologia de lagartas de Spodoptera frugiperda (Smith, 1797) (Lepidoptera: Noctuidae) em soja [Glycine max (L.) Merrill]

Abstract

The fall armyworm Spodoptera frugiperda (Smith 1797) is a pest that attacks several crops of economic importance, such as soybeans. Its importance in the crop has been increasing in recent harvests and is related to injuries caused to leaves and pods forcing producers to perform their control. The objective of this work was to evaluate the non-target effect of insecticides recommended and used to control Bemisia tabaci (Genn.) biotype B on Spodoptera frugiperda. The experiment was conducted at the Laboratory of Applied Entomology, Federal University of Grande Dourados-UFGD, municipality of Dourados (MS). The experimental design was completely randomized, with five treatments, and fifty repetitions. The treatments were: control negative (water), control positive (lufenuron), buprofezin, pyriproxyfen and diafenthiuron. In each repetition, an individualization of a caterpillar occurred in plastic cups, where soybean leaves were offered treated, via spraying, with the maximum dosage of insecticides recommended in a whitefly leaflet. Treatments were evaluated daily during all phases: larval, pupal, adult emergence and fecundity. The results obtained for larval mortality showed that diafenthiuron presented 100% control, followed by pyriproxyfen with 28% and buprofezin with 12%. The duration of the larval period of insects exposed to pyriproxyfen and buprofezin was longer compared with the control treatment. While for the biological parameters of the pupae it was found that pyriproxyfen caused the lowest rate of pupae formation and higher pupal mortality, followed by buprofezin. For adult emergence, pyriproxyfen presented a lower rate, with 13,8% and higher percentage of deformed adults with 60%. Contrary to what most of the current scientific literature cites, we conclude that the insecticides under study cause mortality from S. frugiperda or effects on its biological patterns.