Abstract
In Japan, residual insecticide for stored-grain insect was detected in rice, then the pest control by chemicals in the stage of rice circulation has been prohibited, recently. In this study, to control the stored-rice insect with no chemicales, radio frequency dielectric heating treatments for rice weevil were investigated. It is better to remain the grain temperature low and to heat the insects selectively in the dielectric heating. To find the optimum frequency of the selective heating of the insects, the frequency characteristics of the dielectric constant εr′ and the dielectric loss factor εr″ for both the rice weevil and brown rice were measured. Actually, the dielectric heating treatments for every developmental stage of rice weevil were experimented comparing with the heating by heated air and the mortalities of each developmental stage were examined. As a result, at the range of 10-70MHz the dielectric loss factor of insects was larger than that of grain due to the moisture content difference between insects and grain, and the selective heating of the insects was recognized. It became clear that not only the adult weevils out of grain kernels but also the chrysalises, larvae and eggs in grain kernel were also effectively controlled by dielectric heating.
