Repellence and toxicological activity of the root powder of an invasive alien plant, Chromolaena odorata (L.) (Asteraceae) against Callosobruchus maculatus (Fab.) (Coleoptera: Chrysomelidae)

Abstract

Although several studies have demonstrated the repellent and insecticidal activities of
the leaf extracts or powder of the invasive alien plant, Chromolaena odorata against
stored product pests, studies focusing on the activities of the roots are scarce. The
present study investigated the repellent and insecticidal activity of C. odorata root
powder against the cowpea weevil, Callosobruchus maculatus. Beetle infested cowpea
grains were exposed to two concentrations (2.43 and 3.98 g) of C. odorata root powder
for 12, 24, 36, 48 and 72 hours after which percentage repellence and mortality were
calculated. The root powder of C. odorata significantly repelled C. maculatus, and the
repellent activity was a function of both concentration and exposure time. Following a
48-hour exposure period, 3.98 g of C. odorata root powder exhibited the highest (91%)
repellent activity against C. maculatus. Mortality of C. maculatus caused by the root
powder of C. odorata plants was high and also observed to be concentration and
exposure time dependent. At a low concentration of 2.43 g, C. odorata root powder
accounted for 100 % mortality of C. maculatus after a 72-hour exposure period. This
study demonstrates the potential of C. odorata root powder in the control of C. maculatus
in Nigeria, and portends an avenue for the utilization of an invasive alien weed in Nigeria.

Keywords: Cowpea, Chromolaena odorata, Root powder, Toxicity, Mortality, Repellence,
Callosobruchus maculatus