Laboratory bioassays were conducted in Calabar Nigeria to compare the efficacies of single compounds and the synthetic blends of extracts from A. melegueta and X. aethiopica in controlling Sitophilus zeamais, a primary pest of stored maize in sub-Saharan Africa. Insect culture of the adult S. zeamais was prepared in the laboratory at the University of Calabar to obtain fresh insects for the experimental works. Dried seeds of A. Melegueta (R. schum) and fruits of X. aethiopica (Dunal), A. Rich were procured from a local market in Obudu for the purpose of the work. 100g each of the spice plants were pounded separately using laboratory pestle and mortar for the extraction of essential oils (EOS). The essential oils extracted were tested for repellence and toxicity against S. zeamais at 10µl per essential oil in a 4 –way olfactometer. The chemical constituents of the essential oils (Eos) were isolated and identified and then tested for repellence and toxicity against the S. zeamais. Synthetic blends of the chemical constituents were prepared based on their natural rations. The synthetic blends were also tested for repellence and toxicity against the insect pest. Results indicated that the essential oils and their constituents as individual compounds were significantly (p<0.05) repellent and toxic to S. zeamais. However, the synthetic blends of the chemical constituents were highly repellent and toxic to the insect pest than the single compounds of the essential oils (Eos), thereby providing a broad spectrum of bioactivity against S. zeamais. The synthetic blend of A. melegueta was more repellent to the insect than that of X. aethiopica. This action of the synthetic blends demonstrated their potential for development in Stored Products Protection especially at the small scale resource poor farmer’s level in Nigeria.Keywords:
Laboratory bioassay, efficacy, Sitophilus zeamais, A. melegueta, X. aethiopica, Synthetic blends, Repellency, Toxicity, 4-way olfactometer.