Star anise, Illicium verum Hook f. as a potential grain protectant against Tribolium castaneum (Herbst) and Sitophilus zeamais Motsch

Abstract

Abstract Dried fruits of star anise, Illicium verum, were extracted with hexane and methanol to obtain non-polar and polar fractions, respectively. The insecticidal activity of non-polar crude extracts was tested against eggs, larvae and adults of Tribolium castaneum and adult Sitophilus zeamais. T. castaneum eggs were all killed at 0.01 g ml−1 extract. The adults were more susceptible than the larvae, and younger larvae more susceptible than older ones. S. zeamais adults were twice as tolerant to the non-polar extract as T. castaneum adults. High mortality (70%) of T. castaneum adults occurred in rice treated with the non-polar extract after 21 days' exposure. The effects of polar extracts on the two species of insects were not significant. Adults were allowed to lay eggs in extract-treated rice medium for two days and were then removed. F1 progeny production was monitored. Non-polar extracts completely suppressed F1 adult emergence in both species, while polar extracts only caused a significant reduction in F1 adult emergence. The potential of non-polar star anise extracts as a grain protectant, particularly as an ovicide, is discussed.