Abstract: Laboratory experiments were conducted to establish the efficacy of inert dust –SilicoSec®, Diatomaceous earth (DE) (Bulgarian origin), talcum, calcium carbonate, dicalciumphosphate, zoolite, bentonite and magnezite admixed with stored grain against Rhyzoperthadominica (F.) (Coleoptera: Bostrychidae) The investigation was provided at Plant ProtectionInstitute, Bulgaria, from 2008 till 2010. The results showed that SilicoSec® at doses of 1.5 and2.0kg/t caused 100% mortality to the adults on the 60th and 30th day after treatment, respectively,followed by talcum and calcium carbonate with the same effect at doses 3.0 and 3.5kg/t on the60th day, respectively. Diatomaceous earth and dicalcium phosphate showed same results at ahigher dose – 4.0kg/t. Zoolite, bentonite and magnezite at doses 4.0kg/t caused 87.8, 71.4 and59.3% mortality for the same period, respectively. Among all tested dusts, SilicoSec® was mosteffective against the hidden infestation in wheat grain (to – 28°C and r.h. 75 ± 5%). Only 27insects emerged in F1 generation at a dose of 1.5kg/t and no insects developed by treating with adose of 2.0kg/t. DE and dicalcium phosphate gave similarly results at a dose of 4.0kg/t. Noprogeny developed in F1 and F2 by treating of wheat grain with SilicoSec® at a dose of 2.0kg/t.SilicoSec® was more effective in maize grain, followed by wheat and barley; 100% mortality ofadults was obtained at doses 1.5, 2.0 and 3.0kg/t, respectively.