The present study aimed to investigate the bio-efficiency of five plant powders (clove, black pepper, cinnamon, thyme and capsicum) against the adult stage of the saw-toothed grain beetle, Oryzaephilus surinamensis (L.) under open laboratory conditions at 27.13ºC  and 47.67% RH. The botanical powders were admixed with the standard diet at various concentrations (0.5, 1, 2, 4, 5, 6, 7, 8, 12, 16 and 18 % w/w) and infested by adults  to determine the percentage of adult mortality and some biological effects. The results showed that the percentage of adult mortality increased by increasing both of concentration of the tested plant powder and the exposure period. Generally, clove powder was the most effective plant powder against O. surinamensisrecording the lowest values of LC₅₀  6.787, 5.562, 5.390, 5.256 and 5.256 after 1, 3, 5, 7 and 15 days, respectively. The tested plant powders affected the insect biological characters with various degrees, it was found that both clove and cinnamon powders shortened the growth period, while thyme prolonged the growth period compared to control. All tested powders reduced the progeny number compared to control, whereas clove was the most promising powders in control process where it produced the least progeny number (18.81 insects), while those of capsicum achieved activity on progeny number (64.20 insects). further, all tested powders reduced the percentage of weight loss compared with control.