Egg Developmental Inhibition and Ovipositional Deterrence of Neem or Mineral Oil on Maize Weevil, Sitophillus zeamais Motsch

Abstract

Neem oil, a product from the neem tree (Azadirachta indica A. Juss) was evaluated for its insecticidal properties (ovipositional deterrent and egg developmental inhibitor) against the adult of the maize weevil, S. zeamais. Significantly fewer weevils (22%, p<0.0011 were found on kernels treated with 10,000 ppm neem oil than in the control (78%). Mineral oil had no deterrent effect on weevil distribution at any dose. Although, 1,000 ppm did not deter insects from corn kernels, it significantly affected their oviposition. Neern oil at 10,000 ppm level not only reduced weevil oviposition in the treated kernels but also inhibited their oviposition on untreated kernels in the same area. In no-choice test similar effect on oviposition was also observed. Weevils held for 7 days on corn kernels treated with 1,000 and 10,000 ppm neem oil significantly laid fewer eggs, but when the exposure increased to 16 days, oviposition in the treatment and in the control was the same. All the eggs hatched normally.