Abstract

Laboratory bioassays were conducted on five-selected aqueous plant extracts for contact toxicity and residual action on the brown cocoa mirid, Sahlbergella singularis. The extracts wereMangifera indica (leaf), Anacardium occidentale (leaf), Ocimiun gratissimun (leaf), Azadirachta indica (stem bark) and Acalypha wilkesiana (leaf). Leaf extracts of M. indica, A. wilkesiana and stem bark extract of A. indica applied at 1:5% w/v gave an effective kill of 100, 80 and 80%, respectively, for contact toxicity. M. indica aqueous extract recorded a 100% mirid mortality at the three concentrations tested for 24 h post treatment for residual action, while A. indica gave 89% mortality of mirids at 1:5% w/v. Neem extract was observed to be slow acting. Extracts ofA. occidentale was not efficacious and treatment was not significantly different from that of control (water) at 5% probability level.

Key words: Laboratory bioassay, brown cocoa mired, aqueous plant extracts, toxicity.