The effects of topical application of two essential oils against Sitophilus granarius and Tribolium confusum

Bioassays were conducted to assess the contact toxicity of two plant essential oils against adults of Sitophilus granarius (L.) and Tribolium confusum Jacquelin du Val. Essential oils were extracted from seeds of Carum copticum L. and Cuminum cyminum L. Contact toxicity was assessed by topical application and adult mortality was counted 1, 2, 6 and 24 h after exposure. Bioassays were carried out at 27 ± 1 °C and 65 ± 5% RH in continuous darkness. Results indicated the two essential oils tested were topically toxic to both species. The mortality increased with increase in the oils dose and time exposed to each dose. Adults of S. granarius were more sensitive to C. copticum oil (LD50 = 0.009 μg/mg body wt) than C. cyminum essential oil (LD50 = 0.016 μg/mg body wt). In general, T. confusum showed similar sensitivity to both essential oils. However, adults of T. confusum were more resistant than S. granarius. C. copticum and C. cyminum oils have potential for use in stored-product pest management.