Abstract: Results of laboratory bioassays with diatomaceous earth formulation DEBUZZZER for pre-stored treatment of wheat grain, Triticum aestivum L., against larvae of khapra beetle, Trogoderma granarium Ev., and warehouse beetle, Trogoderma variabile Ball., adults of grain weevil, Sitophilus granarius L., and rice weevil, Sitophilus oryzae L., and confused flour beetle, Tribolium confusum Duv., and larvae and adults of meal-worm beetle, Tenebrio molitor L., are presented. The DEBUZZZER was applied at dose 3 kg per ton. Untreated grain was used as a control. The experiment was carried out in triplicate. Mortality and weight loss of insects were assessed after 3, 6, 9, 14 and 20 days (d) post exposure. Grain quality indicators such as moisture, content of protein and gluten were analyzed after bioassays. Total mortality of adults’ grain weevil (S. granarius) and rice weevil (S. oryzae) has been established on 6 and 14 d after treatment respectively with about 50% weight loss. Also diatomaceous earth treatment of grain has led to a 100 percent death of adults’ mealworm beetle (T. molitor) and confused flour beetle (T. confusum) after 6 and 14 d with 41.8 and 60.6% weight loss respectively. DEBUZZZER was not found to be effective against T. molitor larvae, but caused 100% mortality of hatched adults. Diatomaceous earth formulation was found to be ineffective against T. granarium and T. variabile larvae and has led to 11.7 and 3.3% mortality after 20 d of exposure, respectively. DEBUZZZER wasn’t found to influence on the content of protein, gluten and ash in the grain. However, a small decrease in the moisture content of the grain was detected. Decline of germination of treated seeds wasn’t observed.