Effect of ozone gas on Attagenus fasciatus (Thunberg) (Coleoptera: Dermestidae) and Gibbium psylloides (Czempinski) (Coleoptera: Ptinidae) as stored silkworm product pests

The insecticidal potential of ozone gas was tested against two insect pests of stored silkworm products, Attagenus fasciatus (Thunberg) (Coleoptera: Dermestidae) and Gibbium psylloides (Czempinski) (Coleoptera: Ptinidae). Ozone was tested at three concentrations, 500, 1000 and 1500 ppmv for three exposure times, 1, 2 and 3 h. The adult mortality of two insects was counted during 7 days of treatment. Changes in the morphological features of two insect's adults were examined under scanning electron microscope (SEM) and the chemical composition of treated silkworm cocoons with ozone was determined. Adult mortality of A. fasciatus and G. psylloides was improved with the increase in ozone concentration and exposure time. Thus, all tested concentrations caused complete adult mortality of A. fasciatus after 3 and 5 days of treatment at two exposure times (2 and 3 h), respectively. While the two concentrations of ozone (1000 and 1500 ppmv) caused full mortality of G. psylloides adults after 5 days of treatments at exposure time 3 h. Examination with SEM of treated adults showed induction malformations on the dorsal surface as split between elytra and between the thorax and elytra as well as a split the head capsule from the thorax. Additionally, there was a decrease in the density of some microtrichiae of A. fasciatus. While in case of G. psylloides, observed induction shrinking and deformities occurred in the abdominal cuticles and the abdomen was exploded as results treating of ozone gas. Furthermore, the chemical composition analysis of treated silkworm cocoons showed a slight decrease in protein and carbohydrate contents and increasing at the fat, moisture, fiber and ash contents. Our results indicated that the ozone gas seems to be a promising fumigant for the control of A. fasciatus and G. psylloides.