Evaluation of the efficacy and activity spectrum of six insecticide formulations against cotton pests in Côte d’Ivoire

Abstract

The evolution of the cotton pest complex in Côte d’Ivoire, marked by the emergence of new pests such as Amrasca biguttula, calls for the regular re-evaluation of the efficacy of insecticides used in crop protection. This study evaluated the efficacy of six insecticide formulations compared with an untreated control under farmer field against fruit-boring lepidopterans (Helicoverpa armigera, Earias spp.) and sap-sucking pests (Amrasca biguttula, Aphis gossypii, Bemisia tabaci and Dysdercus voelkeri) at 7 and 13 days after treatment, using analysis of variance and Tukey’s test (5% threshold), complemented by hierarchical cluster analysis. The low pest pressure of H. armigera, A. gossypii and B. tabaci did not allow statistical discrimination among treatments. In contrast, significant differences were observed for Earias spp., A. biguttula and D. voelkeri. Formulations C (teflubenzuron + imidacloprid + lambda-cyhalothrin) and E (bifenthrin + chlorantraniliprole) provided the best control of Earias spp. and D. voelkeri. Fluxametamide (formulation G) exhibited markedly superior efficacy against A. biguttula, achieving a nearly 90%reduction in infested plants. Hierarchical clustering revealed distinct activity profiles, contrasting a formulation specialized against leafhoppers with those having a broader spectrum. Therefore, fluxametamdie is best suited for leafhopper management, whereas formulations combining several modes of action, particularly C and E, provide more balanced protection against the entire pest complex.