Good sanitation and local environment maintenance are generally sufficient to prevent major pest outbreaks. However, if pests have previously been a problem or grain will be stored for an extended period, other options are available to avoid future problems. There are four main modes of pesticide application for stored grain: empty bin sprays, grain protectants, topdressing/pest strips, and fumigation.
After bins have been cleaned, an empty-bin treatment may be applied (see Table 1.3-2 and refer to label to confirm rates). Pay special attention to cracks, crevices, and “hidden” or out-of-the-way spaces. Bins should be sprayed at least 2 to 3 weeks before filling with grain; allow 24 hours for sprays to dry.
Grain protectants are insecticides added to grain as the bin is being filled. These products kill insect pests as they crawl or feed on treated grain. Grain protectant treatments are recommended for grain in extended storage, storage in flat structures, or under conditions favorable to pest development. Protectants may take the form of liquids or dusts; they are generally applied during auguring or loading. Chemical formulations should not be applied before high-temperature drying. If using these products, keep bin temperature and humidity levels low. Heat and moisture shorten the residual life and efficacy of most chemical grain protectants.
Moth pests often enter storage areas from the top surface, so some grain protectants may be applied as a surface treatment. Bacillus thuringiensis (Bt) is a highly selective biological insecticide that provides protection against moth larvae. This may be applied to the surface, or another treatment may be used (see Table 1.3-2). Top- dressing treatments should be mixed into the top 4 inches of the grain. If the surface is already infested with moth larvae (webbing is present), remove the webbing and rake the surface treatment to a depth of 5 inches. Resin strips (dichlorvos or DDVP) can also be hung in the top air space; these strips help control adult moths. Use one strip per 1,000 cubic feet of air space and replace it after 3 months. When using strips, the bin top and roof vent must be temporarily sealed (aeration will make this treatment ineffective). Before re-aerating, remember to open the roof vent.