Effect of wood ash and leaf powder on the fecundity and development of immature stages of sitophilus zeamais (coleoptera: curculionidae)

The maize weevil, Sitophilus zeamais is largely widespread maize pest across the world. It causes important losses of stored maize grain since infestation starts in field and continues in storage. Therefore, an environmentally safe and economically feasible pest control practice needs to be available. The effect of Acacia polyacantha and Hymenocardia acida wood ashes, Plectranthus glandulosus leaf powder and diatomaceous earth (Fossil Shield) was assessed on the development of the immature stages (egg, larva and pupa) and the fecundity of S. zeamais. Ten couples of insects were introduced in maize treated with sublethal contents to allow egg-laying. The number of eggs was counted after staining of infested grain. The batches of infested grain with different immature stages were treated with three contents of each powder. The number of adult emerged was recorded. The number of eggs laid by treated insects decreased slightly by increasing of product content. The application of wood ashes, leaf powder and diatomaceous earth did not suppress completely the development of immature stages. However the number of insects emerging from different stages was considerably reduced compared to the control (0 g/kg). Not significant difference (P > 0.05) was observed concerning the number of insects emerging from different stages at 0 g/kg. The four insecticidal materials substantially reduced the fecundity and the development of immature stages.