Insecticidal Activity of Five Plant Species on Cowpea Weevil [Callosobruchus maculatus (Fabricius)]

A study was conducted to evaluate the insecticidal activity of five locally available plants, namely: Azadirachta indica (Neem), Cymbopogon citratus (Lemon grass), Lantana camara (Lantana), Occimum gratissimum (Scent leaf) and Tagetes erecta (African marigold) on cowpea weevil, Callosobruchus maculatus (Fab.) using the repellency, adult mortality, anti-oviposition and growth inhibition tests. Results revealed that all test materials exhibited repellency against cowpea weevils. Powdered leaves of neem and scent leaf were noted to be slightly more repellent than the others. Cowpea grains treated with powdered leaves of T. erecta exhibited the lowest mortality of the cowpea weevils. Again, A. indica and O. gratissimum treatment were most effective in anti-oviposition and growth inhibitory action, as well as adult mortality of the weevils. Some of the examined treated cowpea grains (except those treated with A. indica and O. gratissimum), had larval tunnels. The total development period of the cowpea weevils that emerged from such treated and the untreated seeds was the same (37days). Botanicals are known to have varying degrees of insect inhibition, and in this case O. gratissimum and A. indica were the most effective.