Ozone as a Potential Fumigant Alternative for the Management of Sitophilus oryzae (Coleoptera: Curculionidae) in Wheat.

Gaseous ozone, an oxidizing agent used as a disinfectant in food processing and preservation, has potential for the control of stored product insects. In this study, we investigated ozone for the management of the rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae), a serious stored product insect pest. We exposed eggs, immature stages within wheat kernels, and adults of the rice weevil to 200-ppm ozone for 12, 24, 36, 48, and 60 h. Insects were placed at 5, 15, or 25 cm depth within a wheat mass in PVC pipes (10 cm in diameter, 30 cm in height) and exposed to ozone. Egg eclosion was recorded 10 d after treatment (DAT), and immature stages were observed for adult emergence 28 DAT. Adults were observed for survival immediately after ozone exposure and again at 1 and 2 DAT. Egg eclosion was significantly lower at 5 cm compared with 25 cm at all exposure times, but not the 12-h exposure time. For each exposure time tested, significantly lesser adults developed from kernels and none of the adults survived at the 5 cm depth compared with the 15 and 25 cm depths. Survival rate of adults was significantly higher at 25 cm depth than at 15 cm depth at the 24-60 h. The deeper the insect in the grain mass, the higher the survival rate. The work reported suggests that ozone is effective in killing all life stages of S. oryzae; however, the efficacy of the gas is dependent on the concentration, exposure time, depth, and gas loss.