Abstract: A laboratory strain of Beauveria bassiana (Balsamo) Vuillemin and a commercial formulation of Bacillus thuringiensis var. kurstaki were assayed against the adult of Rhyzopertha dominica F. under laboratory conditions. Four concentrations of B. bassiana (5 × 106, 5 × 107, 5 × 108 and 5 × 109 conidia /ml) and four of B. thuringiensis (1, 1.5, 2 and 2.5 mg/ml) were used alone against the adult of R. dominica. The mortality was recorded after 1, 3, 5 and 7 days of treatment. Regardless of the pathogen, mortality increased with concentration. Results showed that R. dominica was more sensitive to B. thuringiensis than to B. bassiana. Also, B. thuringiensis caused the highest mortality (93%) at 2.5 mg/ml. In case of B. bassiana, the LC50 value was 5.48 x 107 conidia /ml while the LT50 was 5.45 days at 5 × 109 conidia /ml, whereas the LC50 value of B. thuringiensis was 1.19 mg/ml and the LT50 was 5.05 days at 2.5 mg/ml. These results also showed that the strain of B. bassiana AUMC 3847 isolated from the insect Galleria mellonella could infect the lesser grain borer R. dominica which means no specificity of infection among the strains of B. bassiana and the host insect. Keywords: Pathogenicity, Beauveria bassiana, Bacillus thuringiensis, lesser grain borer.