Potential use of clove and cinnamon essential oils to control the bean weevil, Acanthoscelides obtectus Say, in small storage units

Abstract

The bean weevil, Acanthoscelides obtectus Say, causes severe post-harvest losses in the common bean, Phaseolus vulgaris L. The control of these insects is either non-existent or relies heavily on the use of conventional insecticides, which increase the risks associated with pest resistance, hazards to human health and environmental contamination. Protecting grains with alternative chemical control options that alleviate the concerns outlined above are urgently needed, and essential oils of plants have been presented as a suitable alternative to fill this void. Therefore, this investigation evaluated the non-fumigant applications of clove, Syzygium aromaticum L., and cinnamon, Cinnamomum zeylanicum L., essential oils adequately control A. obtectus on common beans. The oils were tested for insecticidal (lethal toxicities, disturbances on reproductive traits and persistence of action) and repellent activities. Both oil types showed similar toxicity (clove LD=43.6μL/kg beans; cinnamon LD50=46.8μL/kg beans), steadily decreased the growth rate of A. obtectus in a dose-dependent manner, and similarly lost their insecticidal activity over the time. Additionally, the clove oil delayed bean weevil emergence, whereas cinnamon oil repelled the bean weevil. These results indicate clove and cinnamon essential oils as desirable tools for protecting stored beans against A. obtectus in small storage facilities, promoting environmentally friendly pest control strategies.