Cowpea weevil bioassay: A simple prescreen for plants with grain protectant effects

Peasant farmers in northern Nigeria indigenously use various plants to protect cereals and legumes against pest damage during storage. We have developed and employed a simple bioassay technique to assess plants for their ability to protect cowpea from damage by weevil during storage. Of the 10 plants screened, Hyptis suaveolens Poit. (Labiatae) and Sphenoclea zeylanica G earth (Sphenocleacea) showed the best protectant effects after 4 months. The details of the bioassay procedure used and the results obtained are reported.