Insecticidal effects of siliceous sands as preservative for maize and cowpea storage

Siliceous sands were tested in maize and cowpea storage against pests. The purpose of this study is to evaluate the insecticidal activity of two sands applied at increased doses of 1, 2, 3 and 4g/250g of maize and cowpea on Sitophilus zeamais, Callosobruchus maculatus, Prostephanus truncatus and Tribolium castaneum adults. Sands (Diobe1 and 2) were sieved and the two particles sizes retained for the study were 1×1 mm and 0.3×0.3 mm. Untreated plots and Actellic® served as control and the experiment was conducted during one month. Each dose was repeated 4 times. Results revealed a high efficiency of siliceous sand against these four pests with greater efficiency of Diobe1. Mortality of 85% was observed with Diobe 1 against 100% for actellic® and 0% for untreated plots. Emergences progressed inversely to the mortality. Damage and losses reached respectively 25% and 6% with untreated plots. P. truncatus caused nearly 16% of damages and 3% of losses at lower doses. However, with 4g/250g of stored substances (1.6%, w/w), the losses were below 1%. Insects did not show the same sensitivity to treatment and fineness of particles sands inhibits their action as long as the dose increases. (Authors)