Tamiru A, Bayih T, Chimdessa M
This experiment was conducted to determine possibilities of synergism among insecticidal plants against Z. subfasciatus with a view of augmenting potency and reducing dosage rates. Leaf and seed powders of five insecticidal plants, namely Jatropha curcas (L.), Datura stramonium (L.), Chenopodium ambrosioides (L.), Schinus molle (L.) and Azadrachta indica (A. Juss) were mixed to 1% and 2%w/w unitary and binary formulations. The synthetic insecticide primiphos methyl at the rate of 0.1/100 gm grain dust and untreated grains were used as positive and negative controls, respectively. Most binary formulation had better efficacy than their constituent unitary formulation especially at lower dosage rates. Synergistic combination of botanical powders resulted in highest adult mortality, F1 progeny reduction and lowest weevil perforation index and weight loss comparable to chemical standard primiphos methyl. Among the botanical combinations, bean seeds treated with binary formulation of C. ambrosioides with D. stramonium, J. curcas and S. molle gave the best efficacy in controlling Z. subfasciatus.