Toxicity and Repellency of Seven Plant Essential Oils to Oryzaephilus surinamensis (Coleoptera: Silvanidae) and Tribolium castaneum (Coleoptera: Tenebrioidae)

(Ahmed bin Mohammed Al Jabr)

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Abstract

Seven essential oils of Cinnamomum camphora, Cymbopogon winterianus, Matricaria chamomilla, Mentha viridis, Prunus amygdalus var amara, Rosmarinus afficinalis and Simmondsia chinensis were evaluated in the laboratory for their toxicities and repellent effectiveness against adults of saw-toothed grain beetle, Oryzaephilus surinamensis (L.) and rust-red flour beetle, Tribolium castaneum (Herbst). Five concentrations of every essential oil (0.125, 0.25, 0.5 and 0.75 and 1 %) were tested. Adult beetles were exposed to the treated wheat for 2 weeks. Percent of mortality was recorded after 3 days, one week and two weeks from exposure. The repellent action of the previous essential oils was also studied using same concentrations used in toxicity tests. Results showed that complete mortality of O. surinamensis was achieved by M. viridis, M. chamomilla and C. camphora at concentration more than 0.5%. Although, 1% of P. amygdalus or C. winterianus gave complete mortality of T. castaneum after two weeks of exposure. Conversely, R. afficinalis was the least toxic to both insect species. The rest of essential oils gave an adequate toxicity to both insect species. Pronounced increase of mortality was observed for most of essential oils with increasing time of exposure. Tribolium castaneum was less susceptible to tested oils compared with O. surinamensis. Moreover, M. chamomilla exhibited high repellency 81.94% and 84.73% at 1% concentration against O. surinamensis and T. castaneum, respectively.
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