Lethality impact of diatomaceous earth (Sayan®), bran, sawdust and clay on adult of six stored-product insects

Abstract

The lethality impact of diatomaceous earth (Sayan 1 ), bran, sawdust and clay on six major stored-product insects under laboratory conditions was determined. The lethal effects were investigated in two different methods. In the first method, experimental surface was permeated with test material, and in the second method, the test compounds were mixed with rearing mediums separately. In the first technique, adults of Sitophilus oryzae, Rhyzopertha dominica, Oryzephilus surinamensis, Lasioderma serricorne, Cryptolestes ferrugineus and Callosobruchus maculatus were placed in a Petri dish, which was contaminated with a known amount of Sayan 1 , bran, sawdust or clay. Mortality rate was recorded at 24, 48 and 72 h after commence of each exposure. In the second method, the lethality of test compounds which were mixed with wheat was investigated against S. oryzae, R. dominica, O. surinamensis, L. serricorne and C. ferrugineus for 1, 7 and 14 days of exposure. In the first technique, the results indicated that bran and sawdust caused more mortality rate on S. oryzae compared to Sayan 1 . In the second method, the results demonstrated a higher mortality caused by bran and sawdust compared to Sayan 1 on S. oryzae. For L. serricorne, mortality rate caused by bran and sawdust was similar, whereas, in C. maculates case, mortality rate caused by bran was more than the other treatments. The protective effects of test compounds on life span of S. oryzae and R. dominica showed significant differences among the emerged adult of insects in different treatments. In the bran treatment, S. oryzae adult's emergence was the lowest, while, in the R. dominica case, a non-significant difference among resultant number of adult insects was detected.