July 21, 2011

Grain harvested in Nebraska is essentially insect-free, but can become infested by storage insects, which originate in or around the bin or in contaminated equipment such as combines and grain augers. Take time now to clean and prepare bins for this year's grain by following these tips: 

Start with Clean Grain and Equipment

First, be sure to store sound, clean, dry grain. It may be advisable to screen out broken grains, trash and fines to increase the quality of the final storage product. Also, the elimination of trash will enhance fumigation, should this procedure be required later.

Since stored grain insects can invade new grain from infested harvesting and handling equipment (combines, augers, etc.), cleanup is essential. Carefully remove all traces of old grain from combines, truck beds, grain carts, augers, and any other equipment used for harvesting, transporting, and handling grain. Even small amounts of moldy or insect-infested grain left in equipment can contaminate a bin of new grain. Then clean grain bins thoroughly, disposing of spilled, cracked, and broken grain and grain flour, along with the insects feeding on such material. A simple broom and a vacuum cleaner are essential pieces of equipment in cleaning grain bins.

"How clean is clean enough?" is a question many producers ask. A good rule of thumb to follow when cleaning bins and equipment is: If you can tell what was stored or handled last season by looking in the auger, bin, or combine, it is not clean enough to prevent re-contamination of the new crop.

Clear Away Clutter, Landscaping Near Bins

Around the bins, be sure to remove old equipment, junk, and clutter to make the area less attractive to insects and rodents. Make sure that the bin is insect and rodent-proofed by plugging holes, sealing bins, caulking, and making general repairs. Grain spilled near the bin attracts insects and draws mice and rats. Clean up and dispose of any spilled grain several weeks before harvest. If rats have tunneled under foundations, use baits or traps to reduce or eliminate them. Tall weeds can harbor insects and provide cover for rodents. Mow around the bin site to remove tall grass and weeds to reduce the potential for insect and rodent infestation. If necessary, re-grade the site so that water readily drains away from bin foundations. One cannot always wait for the soil to dry before loading or unloading grain from bin sites. Make certain that travel lanes have enough rock or gravel to bear the weight of heavy trucks and grain carts.

Landscaping should be maintained well away from grain storage facilities. Leave a 4-foot wide strip of bare gravel around the perimeter of storage bins. If buying old crop grain for storage with newly harvested grain, watch for insects in the incoming grain. If infested grain is purchased for livestock feed, store it away from the new crop and feed it as soon as possible. Grain stocks may be rotated or moved and a grain protectant applied at the time of turning.

Manage Grain Conditions to Reduce Insect Problems

Stored grain insects cannot live on extremely dry grain (less than 10%); however, it is impractical to reduce grain moisture much below minimum moisture levels necessary for long-term storage. Insect activity and reproduction are favored, however, by high grain moisture (14% or more), especially when condensation and molds occur, and fermentation raises temperature in the grain mass.

Spoilage and internal heating allow insects to remain active even in winter. Manage aeration to manipulate grain temperature. Since insects are "cold-blooded," they are not active much below 50°F, and grain cooling can be particularly important in reducing insect reproduction. Condensation of moisture in the grain mass is prevented by slow cooling and gradual reduction of the gradient between the grain mass temperature and the outside (ambient) temperature.

Check and Repair Mechanical Areas

A bin of 19% moisture corn with a starting temperature of 75°F can lose a full market grade in about five days if the aeration system shuts down, allowing the grain to heat and deteriorate. Electrical system maintenance before harvest can prevent costly downtime. Wiring for fans and other electrical components should be inspected for corrosion and cracked, frayed, or broken insulation. Exposed wiring should be run through waterproof, dust-tight conduit. Avoid kinking the conduit and make sure all connections are secure.

Mice often nest in control boxes where they are protected from predators. They can strip insulation from wires for nest material and their urine sometimes causes corrosion on relays and other electrical components. If rodent damage is found, clean and repair or replace damaged wiring, relays, and other electrical equipment. Then seal over knock-outs and other openings that may permit rodent entry.

Fans, heaters, transitions, and ducts should be checked for corrosion and other damage. Remove any accumulated dust and dirt that may reduce operating efficiency and be sure all connections are tight to prevent air leaks that can reduce operating efficiency.

Treatment of Bins and Stored Grain Insects

Once empty bins have been thoroughly cleaned, a residual treatment may be applied to bin surfaces to protect incoming grain from insect infestation. Follow label instructions carefully. The following materials are listed for empty grain bin surface treatments:

• silicon dioxide, also known as diatomaceous earth – available under many brand names
• Butylcarityl + Pyrethrins – available under many brand names. Related chemicals include Binfenthrin (Capture) and Pybuthryn (Butacide, Pyrenone Crop Spray).

For bins with false floors, which are inaccessible for cleaning, chloropicrin, a bin "clean-out" fumigant, is legal to use, prior to binning the grain.

Other fumigants that could be used on empty bins would be magnesium phosphide and methyl bromide.

Caution! Fumigants are dangerous, restricted-use pesticides and may require gas monitoring devices and respirator protection for the applicator. It is highly recommended that fumigation be done by a commercial pesticide applicator who has been trained and EPA/NDA-certified in safe fumigant handling and application techniques. Refer to current labels for specific details and instructions.

Tom Dorn
Extension Educator