Abamectin induces mortality, inhibits food consumption, and causes histological changes in the midgut of the velvetbean caterpillar Anticarsia gemmatalis (Lepidoptera: Noctuidae)

Abstract

Anticarsia gemmatalis is a defoliator caterpillar of soybean that can be controlled by chemical and biological agents. However, resistant populations of this insect have been reported, which requires research to identify control alternatives. Abamectin acts by contact and ingestion, affecting the muscles and nervous system of insects. However, its effect on other organs has not been evaluated. The present study aimed to evaluate the side effects of oral exposure to abamectin in A. gemmatalis caterpillars. Abamectin is lethal to A. gemmatalis with LC_50/72 h = 96 (74–125) mg a.i. L⁻¹. The survival of caterpillars exposed to different lethal concentrations of this insecticide decreases from 99.9% untreated, to 65.1%, 42.6%, 16.8%, and 0% with the LC_25/72 h, LC_50/72 h, LC_75/72 h, and LC_90/72 h, respectively. Abamectin reduced leaf consumption by A. gemmatalis, indicating an anti-feeding effect. In addition, the insecticide damaged the midgut cells of A. gemmatalis, and caused the degeneration of the peritrophic matrix, disorganization of epithelial striated border, accumulation of mitochondria with different shapes, increased autophagy and release of cell fragments into the midgut lumen. The goblet cells also underwent striated border disorganization in insects exposed to abamectin. The results indicate that abamectin reduces survival and digestive processes of A. gemmatalis after oral exposure and may be an important tool for controlling this pest.