Potential of Lambda-Cyhalothrin for Controlling the Black Armyworm Spodoptera cosmioides (Walker) (Lepidoptera: Noctuidae): Toxicity and Midgut Histopathological Effects.

Abstract

Caterpillars of the genus Spodoptera are the main pests in soybean and cotton crops and Spodoptera cosmioides causes more severe losses than other caterpillars in these agricultural crops. However, there are few recommended insecticides for controlling this pest. Lambda-cyhalothrin is a pyrethroid used to control a wide spectrum of arthropods including lepidopterans. Therefore, the objective of this study was to evaluate the potential of lambda-cyhalothrin for the control of S. cosmioides. Specifically, toxicity and histopathological changes in the midgut were evaluated. The effectiveness of the insecticide was determined by estimating the different lethal concentrations (LCs) ​​in the laboratory upon S. cosmioides. Lambda-cyhalothrin was found toxic to S. cosmioides (LC₅₀ = 23.03 mg L^-1 and LC₉₀ = 174.8 mg L^-1), with the survival reduced from 83.33% in the control to 37.89%, 16.66%, 0%, and 0% after 72 h of exposure to the LC₂₅, LC₅₀, LC₇₅, and LC₉₀ of lambda-cyhalothrin, respectively. Histopathological studies revealed that lambda-cyhalothrin caused damage to midgut cells, including epithelial disorganization, increased cytoplasmic vacuolization, brush border degeneration, nuclear chromatin condensation, and cell fragmentation, indicating cell death by apoptosis. It was concluded that lambda-cyhalothrin, a neurotoxic insecticide, caused damage to the midgut of S. cosmioides, compromising its physiology and indicating that it has potential to be used to control this pest.