Protecting and disinfesting stored products by drying and cooling, and disinfesting stored products during handling by mechanical treatments

Drying and cooling nonperishable products sufficiently to achieve effective protection or disinfestation has been considered difficult in the case of the former and mostly impractical in the case of the latter. Physical methods of disinfestation that could be incorporated into the handling process, such as cleaning and mechanical impact have either not given complete pest control or have caused unacceptable grain damage. Thus chemical options, particularly phosphine fumigation, have remained the main method of pest control. However, minimal use of chemical treatments is becoming increasingly necessary. Apart from market forces and stricter food safety standards, insect resistance to phosphine is growing and chemical alternatives are limited. In light of these circumstances, this paper reviews the effectiveness of grain drying and cooling not only as a means of protecting against insects and mites during storage, but also as a means of disinfesting during the drying and cooling process. Opportunities are identified that might capitalize on a specific pest’s response to such conditions. The level of pest control that can be achieved when manipulation of grain temperature and moisture is used in conjunction with mechanical disinfestation is also considered. Recent studies of grain cleaning are reviewed and fresh data from mechanical impact research are presented on the mortality of Sitophilus oryzae, Rhyzopertha dominica and Tribolium castaneum. These data show real promise that mortality of insect development stages within grain kernels can be obtained at levels above 99% without damage to commodities such as wheat, which would overcome a major limitation to the technology. The results of the mechanical disinfestation research are discussed as part of a pest control strategy that includes the combined effects of grain drying, cooling and handling, to help deliver pesticide-free grain and extend the life of phosphine by restricting the development of resistance. Keywords: Drying, Cooling, Handling, Aeration, Mechanical impact, Disinfestatio