Insecticidal activity of Croton hirtus l’her extracts on Callosobruchus maculatus as a preservative measure for stored cowpeas

Abstract

Croton hirtus L’Her (Euphorbiaceae), known as hairy croton, is popular in traditional medicine for the treatment of fever, inflammation,  diabetes and cancer amongst others. Insecticidal activities of hexane and acetone extracts of C. hirtus aerial parts at 0.1 - 0.8 g per 50  cowpea seeds, and standard insecticide, permethrin at 1.5 and 3.0 mg, as seed dressings, were assessed using standard methods.  Oviposition at 15 days after treatment (DAT) and adult insect emergence (F1 generation of Callosobruchus maculatus) at 50 DAT were  determined. In addition, parameters of seed damage were assessed. The result indicated differences in insecticidal effects between the  different concentrations of the extracts used. Acetone extract (ACT) was more effective than hexane extract (HXN) in inhibiting both  oviposition and adult emergence at all tested concentrations. ACT gave higher oviposition deterrency (80.33vs12.91%) and inhibition of emergence (88.79%vs60%) than HXN at the peak concentration. ACT was comparable to 3 mg permethrin in adult inhibition (81.59%) but  more effective in oviposition deterrency (58.42%). It also exhibited greater reductions in all parameters of seed damage, and higher  percentage protectant ability (56.14%) than HXN. Based on these indices, C. hirtus ACT was comparable to the standard insecticide,  permethrin, and has demonstrated potential as an effective bioinsecticide against cowpea weevils in the preservation of cowpea seeds.