Ozone technology in the post-harvest storage environment- a comparison of efficacy of high doses of ozone to insects treated under laboratory conditions and field conditions

Efficacy experiments were conducted to determine the ozone concentration (C) and treatment time (T) needed to effectively kill adult stages of red flour beetle (i>Tribolium castaneum) and maize weevil (Sitophilus zeamais). Under laboratory conditions, insects were exposed to concentrations of ozone ranging from 50 to 1800 ppm for 30 and 60 min. After treatment, insect mortality was scored, and if 100% mortality was not reached, more treatment-time was added in 30 min intervals at 1800 ppm. For both species, 100% mortality was reached after treatment at 1800 ppm for 120 min, which equates to a concentration*time (CT) product of 216,000 ppm.min. A similar CT product was attained under field conditions with a prototype auger designed to treat moving streams of grain with ozone during transfer. In field tests, 100% mortality was achieved for both insect species after a treatment of 47,000 ppm ozone for 6 min (CT = 282,000 ppm.min). The results indicate that CT values obtained in laboratory experiments correlated wll with those from field experiments. Based on these results, we now can calculate ozone concentration and auger length needed to treat grain in a fast-moving stream. Keywords: Ozone, Maize weevil, Sitophilus zeamais, Red flour beetle, Tribolium castaneu