INSECTICIDAL ACTIVITY OF SYNTHETIC 2-CARBOXYLBENZOFURANS AND THEIR COUMARIN PRECURSORS

Several 2-carboxylbenzofurans and their coumarin precursors, compounds 1-6, and the novel compound 7 were synthesized and their insecticidal activity studied using adult sweet potato weevils (Cylas formicarius elegantulus (Summer)) at 24 mu g, 48 mu g and 72 mu g per insect in 0. 5 ml litre(-1) piperonyl butoxide (PPB) in acetone. The order of toxic ity of the compounds as judged by the percentage mortality at 24 mu g per insect at 48 h was 2 (100%) > 6 (95%) > 7 (85%) > 4 (75%) > 3 (65% ) > 1 (60%) > 5 (45%) > piperonyl butoxide (0.0%). Compound 2 was equi toxic to 24 mu g of technical grade dimethoate. When administered in a cetone alone, however, the compounds were only moderately active (i.e. > 120 mu g per insect was required for 60% mortality at 48 h). The te st compounds were more active at lower doses (48-72 mu g per insect) w hen dissolved in dimethylsulfoxide or in an oil extract obtained from the fruit of Blighia sapida Koenig.