Lethal effect of ozone gas on the adults of Sitophilus oryzae (Coleoptera : Curculionidae) and Oryzaephilus surinamensis (Colioptera : Cucujidae)

Effect of ozone on the adult mortalities was investigated in the rice weevil, Sitophilus oryzae (L.) and the saw-toothed grain beetle, Oryzaephilus surineamensis (L.). The insects were exposed to flow of ozone of amount ranged from 0.66 to 0.83 mg/min. The exposure periods were 10 to 300 minutes for the rice weevil and 1 to 18 hours for the saw-toothed grain beetle. Mortality counts were made at each of the ten days after exposure. The rice weevil was highly sensitive to ozone and temporarily fall into a state of coma after more than 90 minutes exposures. The LT50 and LT95 values at the tenth day after exposure were about 25 and 70 minutes for the rice weevil and about 10 and 100 hours for the saw-toothed grain beetle. The saw-toothed grain beetle was about 86-fold more tolerable to ozone than the rice weevil.