Heating for disinfestation has been practiced of at the condition of 55-60°C for at least 48 hours in various facilities of stored and processed agricultural products. However, it has been required to reduce temperature and time due to the economic efficiency. To improve disinfestation efficiency of heating, we demonstrated whether combined treatments of heat with other agents exert synergistic for disinfestation. Heat treatments were combined with 1 ppm diatomaceous earth (DE), 10 ppm phosphine or 10% carbon dioxide against Plodia interpunctella, Sitophilus zeamais and Tribolium castaneum. Insects were treated single or multiple combinations of each component for 6 h at either 25°C or 40°C, then mortalities were monitored for 14 days post-treatments. Combined treatments greatly enhanced mortalities and shorten killing time of three species rather than single treatments. Particularly, heat treatments with 1 ppm DE and 10 ppm phosphine completely lethal within 3-6 h post-treatments, but heating with 10% CO2 was not much effective. Among three species, S. zeamais adults were more suscpetable to heat but both larvae and adults of T. castaneum was highly susceptible to phosphine. Our results clearly showed that combined treatment of DE or phosphine with mild heating (40°C) greatly improved mortalities of three major stored pest insects and provide advanced techniques for disinfestation of stored product pests.

Plodia interpunctella, Indianmeal moth, is world-widely distributed pest in stored and manufactured agricultural products. Practically, this species seriously damaged by the infestation of most stored and manufactured agricultural products. It is necessary to find useful techniques for the control of stored-product pests insects including P. interpunctella. Recently, heating at 55℃ for 48 h can be practically used to disinfest stored-product insects in the filed of manufactures. To improve efficiency of this technique we conducted combination treatments with heat and diatomaceous earth. At room temperature, wandering larvae, which is most tolerant developmental stage to heat, were not dead regardless of diatomaceous earth (4 mg/L) treatment within 24 h. However, incubation at 40℃, all the larvae were dead with diatomaceous earth treatment while its mortality was 28% without diatomaceous earth treatment. Thus, heating effects was significantly improved by the combined treatments of diatomaceous earth. This effect was increased when temperature was higher and the exposed time is longer. Our results clearly showed that the combined treatments of both heat and diatomaceous earth showed synergistic effects for the control of P. interpunctella.