Insecticidal effect of ozone on larvae of Tenebrio molitor and their enzyme activity

Abstract Tenebrio molitor L. is insect pest of commodities and stored products. The effect of ozone gas was evaluated on the larval mortality T. molitor at four concentrations of 250, 500, 1000 and 1500 ppmv and 0.5, 1.0 and 2.0 h of exposure. Our results demonstrated that the mortality rate of T. molitor treated larvae increased progressively as exposure time or ozone concentration increased. The ozone concentrations of 1000 and 1500 ppmv at exposure time of 2.0 h were more effective than lower concentrations on larval mortality (63.4 and 71.4%) and (75.6 and 85.7%), respectively, after 1 and 3 days of treatment. After 5 days of exposure, the same concentrations at 2.0 h of exposure time induced strong larval mortality (82.9 and 92.9%), respectively. The full larval mortality (100%) obtained by 1500 ppmv of ozone for 2.0 h of exposure after 7 days. Furthermore, our results demonstrated that ozone caused increasing in enzymes activities of phenoloxidase, peroxidase, glutathione S-transferase, general-esterase, adenosinetriphosphatase and lactate dehydrogenase of treated larvae of T. molitor compared with untreated larvae. According to our research, ozone could be an effective fumigant for controlling of this insect pest.