Damage of Major South American Lepidopteran Soybean Pests

Abstract

Lepidopteran pests are major factors limiting soybean productivity in South America. In some cases, the control of these species requires the use of foliar insecticides. For a sustainable use of these insecticides, they should be sprayed when insect population sizes reach an economic threshold. Since this estimation requires to determine the consumption of different species, this work aimed to integrate all the main factors, studying the consumption of small- and medium-size larvae of major lepidopteran pests to vegetative and reproductive tissues on Bt and non-Bt soybeans. The damage to vegetative tissues was tested in detached-leaf assays in grow chambers, and to reproductive structures was measured in greenhouse with infestation at early (flowering) and mid reproductive (mid grain filling) stages. Based on the feeding behavior of the species tested, they were cast in four groups: a) A. gemmatalis and C. includens, defoliating only the RR variety with the lowest consumption of foliar area; b) S. eridania, defoliating both RR and IPRO varieties, consuming twice than the species mentioned above; c) H. armigera, defoliating and being the most damaging species to pods in the RR variety; d) S. cosmioides and S. frugiperda, defoliating and damaging pods in both varieties. The species differed in their ability to feed on IPRO varieties, so a different economic threshould could be considered. This clasification contributes to a recommendation of insecticide use sustainable, taking into account the behavior of these species that are major soybeans pests in South America.