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Preliminary investigations with ethanolic (EtOH) extracts from five Nigerian plants show that extracts of Piper guineense Schum and Thonn (Piperaceae), Cedrela odorata L. (Meliaceae), Dennettia tripetala G. Baker (Annonaceae) and Aframomum melegueta (Rosch) K. Schum (Zingiberaceae) in artificial diets significantly reduced larval growth of European corn borer (ECB), Ostrinia nubilalis Hubner, at a concentration of 1000 ppm (0.1%). An extract of Xylopia aethiopica (Dunal) A. Rich (Annonaceae) was ineffective. When the extracts were subsequently incorporated into artificial diets at 300 ppm and offered to neaonates, larval mortality increased in the order A. melegueta (13%), D. tripetala (13%), P. guineense (27%), and C. odorata (48%). Larval and adult emergence periods increased with increasing concentration of P. guineense, C. odorata and D. tripetala indicating a toxic response. Nutritional indices for habituated third instar larvae with the two most promising plant extracts, P. guineense and C. odorata, showed that the efficiencies of conversion of digested food (ECD) was significantly reduced at 300 ppm suggesting a postdigestive toxicity of the extracts. P. guineense and C. odorata extracts show the best potential for development as botanical insecticides.

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A standardized twig extract of the Asian shrub, Aglaia odorata Lour. (Meliaceae), and rocaglamide, a purified active principle of the extract, were evaluated for potential to control the European corn borer (Ostrinia nubilalis Hübn.), via incorporation into meridic diet fed to larvae. Life cycle bioassays using the extract revealed that it inhibited larval growth at all concentrations tested (12.5–100 p.p.m./fresh wt.) and delayed mean time to pupation from 24.1 days (control) to 83.8 days (50 ppm). Other effects include reduced pupal and adult weights and an increase in the frequency of deformed pupae. Investigation of consumption rates and dietary utilization in larvae feeding on diet containing the extract suggested that it acts via a combination of antifeedant and postingestive (toxic) actions. Life cycle bioassays using rocaglamide demonstrated that this compound is an extremely potent inhibitor of larval growth, with concentration dependent activity observed at dietary concentrations from 0.05‐0.02 ppm. Effects at these levels include severe reductions in growth and pupal weight, and increases in larval mortality and time to pupation. Rocaglamide appears to be as, or even more active, than the very effective botanical pesticide azadrachtin from the neem tree.

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