Efficacy of the stem powder of an invasive alien plant, Chromolaena odorata   (L) (Asteraceae) against Callosobruchus maculatus   (Fab.) (Coleoptera: Chrysomelidae)

This study investigated the repellent and insecticidal activities of the stem powder of C. odorata against a serious economic pest of cowpea, Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae). Cowpea grains infested with ten (10) 1 – 2 day old unsexed adults of C. maculatus were exposed to three concentrations (0.0, 2.6 and 5.0 g) of C. odorata stem powder after which percentage repellency was monitored for 12, 24, 36 and 48 hours and mortality for 12, 24, 36, 48 and 72 hours. Results from this study revealed that the stem powder of C. odorata exhibited significant repellent activity against C. maculatus, although it was a function of both concentration and exposure duration. Following a 48 – hour exposure period of C. maculatus to the stem powder of C. odorata, the highest concentration (5.0 g) was observed to demonstrate the highest percentage repellent activity (87%). Similarly, mortality of C. maculatus caused by the stem powder of C. odorata was high and observed to be concentration and exposure time dependent. At the lowest concentration (2.6 g), the stem powder of C. odorata accounted for 100% mortality of C. maculatus after a 72 – hour exposure period. In summary, this present study clearly demonstrates the repellent and insecticidal activities of C. odorata stem powder and further suggests its usage as an attractive alternative to synthetic insecticides in the management of C. maculatus infestation in Nigeria and elsewhere.

Keywords
Cowpea; Chromolaena odorata; stem powder; toxicity; Mortality; repellency; Callosobruchus maculatus