Evaluation of Binary Combination of Rice Husk Ash With Some Other Insecticidal Plant Powders in Grain Protection Against Damage by Two Storage Beetles

Evaluation of protectant ability of Jemila rice variety husk ash (JRHA) in binary combination with some other insecticidal plant powders against grain damage by the cowpea seed beetle, Callosobruchus maculatus (F) and the maize weevil, Sitophilus zeamais (Mots), was conducted at the Research Laboratory of the Department of Crop, Soil and Pest Management, Federal University of Technology, Akure, Ondo State, Nigeria, under ambient temperature of 28 ± 2 °C and 70 ± 5% relative humidity. Each binary combination was in the 1:1 ratio and was applied and evaluated at different dosages of 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0 g/20 g of grain, against ten paired adult beetles for C. maculatus and ten unpaired adult beetle for S. zeamais. Irrespective of beetle or and weevil species, dosage and time of observation, all the binary combinations protected grain from damage significantly in comparison with the control. The JRHA and E. aromatic combination proved generally superior to the other combinations in protecting grain from damage by the two beetles with respect to lethality to adults, inhibition of oviposition, reduction in F1 adult emergence and grain weight loss. The mixture had the lowest LD50 for the two beetles. The JRHA and P. guineense combination closely followed the JRHA and E. aromatica combination in superiority for grain protective ability against damage by the beetles. They may be recommended for use by grain handlers to mitigate damage by C. maculatus and S. zeamais. They could also be included as a component of integrated grain protection strategies.