Effects of alcoholic leaf and seed extracts of Datura innoxia on the reproductive performance and behavioral responses of southern cowpea beetle, Callosobruchus maculatus

Abstract

Botanical insecticides are a sustainable option to synthetic compounds in controlling insect pests of stored grains and products. Datura innoxia contains bioactive alkaloids with established insecticidal and behavioral activity, however, its activity, against the southern cowpea beetle, Callosobruchus maculatus, is poorly studied. This research was carried out to explore the alkaloid profiles of alcoholic extracts of D. innoxia leaves and seeds on reproductive performance of C. maculatus as well as behavioral responses. The alkaloid richness of the plant was confirmed by the presence of two major tropane alkaloids in the leaf extract, hyoscyamine (5.1 ppm; retention time 3.68 min) and scopolamine (7.8 ppm; retention time 0.6 04 min) as revealed by high performance liquid chromatography analysis. The treatment of cowpea seeds using alcoholic leaf extracts caused a significant reduction in oviposition of C. maculatus females. Seed extracts performed better than leaf extracts. Treatments did not show any major variations among concentrations, which led to a high process of activity even in case of low doses. The assays conducted with repellency showed concentration-based effects, the highest repellency rates of 80 and 90 percent respectively were observed when leaf and seed extracts were used at a 3000 ppm concentration. The highly decreased reproduction and the effective repellencies can be linked to the toxicity of alkaloids, oviposition and disruption in insect-development. In general, the results demonstrate the potential of D. innoxia, especially seed extracts, as a green and efficient botanical protectant to preserve cowpea seeds.