Bioactivity of essential oils from five spices against Sitophilus zeamais Motschulsky (Coleoptera:Curculionidae)

Abstract

Sitophilus zeamais is a serious pest of stored products in worldwide. We report for the first time on the repellent and contact toxicity of the essential oils of Myristica fragrans, Cinnamomum verum, Pimenta racemosa, Syzygium aromaticum and Cuminum cyminum against an important stored product pest, Sitophilus zeamais feeding on Pisum sativum. Eugenol was the dominant constituent of both P. racemosa (76.9%) and S. aromaticum (55%), while cinnamaldehyde (62%), cuminaldehyde (89.8%) and elemicin (59%) were the most prevalent components of C. verum, C. cyminum and M. fragrans respectively. Essential oils of M. fragrans, P. racemosa, C. verum and S. aromaticum were repellents at concentrations of 4 and 8µL/mL. M. fragrans essential oil was the most toxic against S. zeamais with 100% mortality occurring within 2 days at 100µL/mL. Significant mortality was also observed with C. verum essential oil causing 78% and 97% of deaths at concentrations of 75 and 100µL/mL respectively. The LC50 values for M. fragrans and C. verum oils were 10.16 and 56.47µL/mL with the corresponding LT50 values of 1.44 and 2.48 days respectively. These results indicate that the essential oils from M. fragrans and C. verum may be explored as potential natural repellent and contact insecticides against S. zeamais in stored products.