Efficacy of Ozone against Phosphine Susceptible and Resistant Strains of Four Stored-Product Insect Species.

The efficacy of ozone was evaluated against four economically-important stored-product insect species at 27.2 C and 20.4% r.h. Adults of phosphine-susceptible laboratory strains and phosphine-resistant field strains of the red flour beetle, (Herbst), saw-toothed grain beetle, (Linnaeus), maize weevil, Motschulsky, and rice weevil, (Linnaeus), were exposed in vials to an ozone concentration of 0.42 g/m³ (200 ppm) for 1, 2, 3, 5, 6, 8, 10 and 12 h with 0 and 10 g of wheat. Initial and final mortalities were assessed 1 and 5 d after exposure to ozone, respectively. After an 8-12-h exposure to ozone, initial mortality of spp. and was 100%, whereas the highest initial mortality of was 90%. A 3-4-h exposure to ozone resulted in 100% final mortality of spp., whereas required a 6- to 10-h exposure to ozone. Adults of were least susceptible to ozone, and after a 10-h exposure, mortality ranged between 82 and 95%. Time for the 5 d 99% mortality (LT) for adults of laboratory and field strains of spp., and were 2.00-5.56, 4.33-11.18 and 14.35-29.89 h, respectively. The LT values for adults of and were not significantly different between bioassays conducted with 0 and 10 g of wheat. The LT values for the laboratory strains of spp. in the absence of wheat were significantly lower than those obtained in the presence of wheat. Both phosphine-susceptible and -resistant strains were equally susceptible to ozone. Ozone effectively suppressed adult progeny production of all four species. Ozone is a viable alternative fumigant to control phosphine-resistant strains of these four species.