Effect of Diatomaceous Earths on Mortality, Progeny and Weight Loss Caused by Three Primary Pests of Maize and Wheat in Kenya

Abstract

The Kensil fine (KF) dust was evaluated under laboratory conditions for the control of three important storage insect pests of maize and wheat. Serial concentrations of KF, Dryacide (DA) and Wood ash (Ash) were admixed with 100g of maize or wheat in ventilated glass jars. Mortality of S. zeamais, P. truncatus and R. dominica was assessed at 7, 14, 28, 56 and 84 days interval after grain treatment. At 28 days, all the three dusts effectively controlled S. zeamais with 95% - 100% mortality while only DA was effective against P. truncatus. Both KF and Ash, with 84% and 92% mortality, did not reach the threshold required for P. truncatus. Mortality in R. dominica only peaked after 56 days but again only DA treatment was effective at 84 days. The delayed effect of the Diatomaceous earths (DE) and ash treatments appear to contribute to the higher damage inflicted; hence more weight loss than was expected. At 28 days mean sample weight loss by S. zeamais was 4.5% while P. truncatus and R. dominica caused 4.2% and 3.5% respectively. The emerged progeny after 14 days exposure to the three dusts was different for each pest with DA producing the least and KF the most. These results formed the criteria on which to base future trials under simulated farmer storage practice.