The Lethal impact of diatomaceous earth and kaolin on adult of four stored-product insects

The lethal impact of Kaolin (Clay®) and diatomaceous earth (Sayan® and SilicoSec®) on four major stored-product insects was determined under laboratory conditions. The lethal effects were investigated in two different methods. In the first, experimental surface was permeated with test material, and in the second method, the test compounds were mixed with rearing mediums separately. In both techniques, adults of Sitophilus granarius, Tribolium confusum, Oryzaephilus surinamensis and Cryptolestes ferrugineus were placed in a petri-dish, which was contaminated with a known amount of Sayan®, Clay® and SilicoSec®. In the first method, mortality rate was recorded after 24, 48 and 72 h of exposure. In the second method, the lethal impact of test compounds which were mixed with wheat was investigated against S. granarius, T. confusum, O. surinamensis and C. ferrugineus for 1, 7 and 14 days of exposure. In the first technique, the maximum mortality rate was achieved with SilicoSec® (88.56%) and Sayan® (75.85%) on S. granarius and C. ferrugineus respectively. In the second method, the results were demonstrated, the maximum mortality caused by Sayan® (88.56%) SilicoSec® (75.68%) and Kaolin® (55.25%) in S. granarius. In S. granarius case, mortality rate caused was more than the other species. The protective effects of test compounds on life span of S. granarius and T. confusum showed no significant differences among the emerged adult insects in Sayan® and SilicoSec® treatments while showed significant differences among the emerged adult of insects in Sayan® and SilicoSec® with Clay®.