Contact toxicity, repellent activity and residual effect of Syzygium aromaticum L. (Myrtaceae) and Piper nigrum L. (Pipeaceae) powders against Sitophilus oryzae L. (Coleoptera: Curculionidae)

Abstract

Weevils are important pest of several stored food and their products. Reducing post harvest losses is a resource-efficient way of increasing food availability. The contact toxicity, repellent activity and residual effect of clove and pepper powders were evaluated against rice weevils. Results showed that there were significantly differences between clove and pepper. The percentage mortality in clove was higher than in pepper powder. Whereas the LD50 values were 7.67 and 12.83% after 24 hours for clove and pepper, respectively. Clove was more toxic than pepper against the rice weevils after 15 days of exposure. But pepper was more persistence than clove, LT50 values were 52.5 and135 days for clove and pepper, respectively. Moreover, Pepper was more repellency than clove. The percentage repellency values of pepper were fluctuated at all concentrations and times of exposure. It can conclude that, clove and black pepper powders can be used as natural protectants of stored grains to reduce the usage of the synthetic insecticides.