Evaluation of the repellent and insecticidal activities of the leaf, stem and root powders of siam weed (<i>Chromolaena odorata</i>) against the Cowpea Beetle, <i>Callosobruchus maculatus</i>

Abstract

This study investigated the repellency and toxicological activity of C. odorata root, stem and leaf powders against adults of the cowpea beetle, Callosobruchus maculatus (Fab.) (Coleoptera: Chrysomelidae). Adults of C. maculatus were exposed to grains treated separately with the root, stem and leaf powders of C. odorata at different exposure periods of 12, 24, 36, and 48 hours. All the three plant parts significantly repelled C. maculatus with the root powder showing the highest percentage repellency, although this was a function of exposure time. The order of repellency after 48 hours exposure was 88, 83 and 76% for the root, leaf and stem powders, respectively. Powders from the three plant parts exhibited insecticidal activity by causing varying levels of mortality to C. maculatus with mortality increasing with increase in exposure time. The root powder accounted for the highest adult mortality (74%) while the leaf powder accounted for the least mortality (51%) after 48 hours exposure time. The high repellent and insecticidal activities demonstrated by the root powder compared to the leaf and stem powders suggest that the root powder should be prioritized for the control and management of C. maculatus.

Keywords: Chromolaena odorata, plant powder, toxicity, mortality, repellency, Callosobruchus maculatus