Fumigant and contact toxicities of individual and additive combinations of biorational-essential oils for control of rice weevil (Sitophilus oryzae)

Fumigant and contact activity of individual and combination of EOs (cumin seed and black pepper oil) were conducted against rice weevil (Sitophilus oryzae). Cumin seed and black pepper oil individually exhibited 100% insecticidal activity (Contact and Fumigant) against S. oryzae at 24 and 168 h of exposure in the absence and presence of food, respectively. Overall, differential insect mortality rates were observed with individual EOs; however, cumin seed EO showed higher insecticidal activity in both fumigant and contact bioassays than black pepper EO. Binary mixtures of cumin seed and black pepper oil at 60:40 and 80:20 ratios showed higher toxicity than individual EOs against S. oryzae and further, additive interaction of binary combinations of EOs resulted in complete insecticidal activity of S. oryzae. Thus, we conclude binary mixtures of cumin seed and black pepper EOs might be a promising prophylactic treatment solution for control of S. oryzae to prevent stored grain infestation.