Potential of cloves (Syzygium aromaticum (L.) Merr. and Perry as a grain protectant against Tribolium castaneum (Herbst) and Sitophilus zeamais Motsch

Abstract

The flower buds of cloves were extracted with methanol or hexane. The methanol (polar) extracts were tested against Tribolium castaneum and Sitophilus zeamais adults via topical application. The hexane (non-polar) extracts were tested against the two insect species by filter paper impregnation. No contact toxicity of polar extracts was observed for either insect species. However, 100 g/100 ml [100% (w/v)] non-polar extracts caused 90% mortality in S. zeamais but had no effect on T. castaneum. Both polar and non-polar clove extracts were applied to milled rice which was then exposed to the two species of beetles separately in treated medium tests. The polar fractions had no effect on the mortality of both species of insects. However, with the non-polar extracts, mortalities of 13% and 44% in T. castaneum were obtained after 7-day and 21-day exposure periods respectively. For S. zeamais mortalities of 43% and 53% were observed after 7 and 21 days of exposure respectively to rice treated with the non-polar extracts. After removal of the treated adults of both species at the end of the 7-day exposure period, the emergence of the F1 progeny was monitored. No progeny of T. castaneum emerged from the rice treated with non-polar extracts while extremely low emergence of S. zeamais was observed.