Sensitivity of Helicoverpa armigera to emamectin in the Commune of Djidja in southern Benin

Abstract

Helicoverpa armigera is recognized as the most dangerous pest of cotton cultivation in Benin. Repeated use of active ingredients leads to habituation of pests. Thus, monitoring the sensitivity of pests to commonly used active ingredients is necessary to determine when this chemical family may lose its effectiveness to be replaced in cotton protection programs. Following alerts of ineffectiveness of Thalis 112 EC by cotton producers in the commune of Djidja, a study was initiated to evaluate the sensitivity of H. armigera to Thalis 112 EC (Emamectin 48 g/l and acetamiprid 64 g/l). Thus, caterpillars were collected in 2021 in three villages in the commune of Djidja and then vial-tests were carried out at the same concentration as that recommended to producers in two villages with mortality counts at 24 hours, 48 hours and 72 hours. The results of the average survival rate of the caterpillars showed that the two strains (KAK01/09-BJ.cot and LIN08/09-BJ.cot) had a zero survival rate in 24 hours while the survival rate of the controls varied between 70 % and 80 %. Thalis 112 EC remains an effective alternative against H. armigera in the commune of Djidja.