Efficacy of abamectin and emamectin benzoate alone or in binary combinations with carvone, p-cymene and menthone for the control of Callosobruchus maculatus

Abstract

The toxicity of two microbial insecticides, abamectin (AB) and emamectin benzoate (EM) at 0.25 and 0.5 mg/kg, and three monoterpenes, carvone (CA), p-cymene (CY), and menthone (ME) at 0.625, 1.25, and 2.5 g/kg and their combined treatments was assessed against Callosobruchus maculatus (F.) on cowpea seeds. Adult mortality (after 3 and 7 days), progeny production (after 45 days), and weight loss in cowpea seeds were checked for all individual and combined treatments. Seven days post-exposure, the highest concentrations of most insecticides/monoterpenes combinations showed a total adult mortality (100 %). Similarly, no progeny was observed at the highest rates of combined treatments, especially when EM mixed with either CA or ME. In addition, all combinations of tested monoterpenes and microbial insecticides decreased or suppressed the damage caused by cowpea beetle on seeds and gave a complete protection for the cowpea seeds for 45 days. These findings indicate that combinations of microbial insecticides with monoterpenes could be a useful approach for the effective control of C. maculatus on stored cowpea seeds.