Harvested grain is essentially insect free, but it can become infested by storage insects, which originate in or around the bin or in equipment like combines and grain augers.

Cleaning and preparing bins and harvesting equipment now can help ensure that grain insects don't infest your grain and diminish the value of your harvest later, says Tom Dorn, a University of Nebraska Extension educator.

Dorn offers the following tips:

  • Carefully remove all traces of old grain from equipment, including 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.
  • 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 when cleaning grain bins. The earlier bins and equipment are cleaned, the less likely it is that insects will survive until harvest. A good goal would be to clean all your bins and equipment of grain and grain dust at least 30 days before harvest begins.
  • Check the grain bin foundation to ensure it's solid and can bear the needed weight. A 9,000-bushel bin is supporting more than 500,000 pounds of grain besides the weight of the bin and the concrete pad. Cracks will weaken the foundation and could be a source of pest problems. Also, be sure to remove old equipment, clutter and tall weeds to reduce attractiveness to mice and rats, which like to burrow under the bin foundation. Control rodents with bait or traps as necessary. Regrade the site if necessary, so water readily drains away from bin foundations.
  • Make sure that travel lanes have enough rock or gravel to bear the weight of heavy trucks and grain carts when the soil is wet. You can't always wait for the soil to dry before loading or unloading grain from bin sites.
  • Check control boxes for rodent damage. Mice will strip insulation from wires for nest material and their urine can corrode relays and other electrical components. If you find damage, repair or replace the damaged parts, then seal over knock-outs and other openings that may permit rodent entry.
  • Check fans, heaters and ducts for corrosion and other damage. Remove any accumulated dust and dirt that will hold moisture and promote rust. Be sure all fan, heater and transition duct connections are tight to prevent air leaks that can reduce operating efficiency.
  • Once empty bins have been thoroughly cleaned, a residual insecticide treatment may be applied to bin surfaces to protect incoming grain from insect infestation. Follow label instructions carefully. Following are some materials for residual treatment of empty grain storage areas:
    • Diacon II
    • Strike Ultra
    • Drione Insecticide
    • Evercide MC
    • silicon dioxide (Insecto and Protect-It)
  • If the bin has a raised drying floor and was known to be infested with grain storage insects last season, consider hiring a professional pest control operator to fumigate the empty bin prior to filling with new grain.

Harvest — Store to Maintain Quality

Dorn says you should never put new grain on top of old grain because of the risk of infesting the new grain with storage insects and mold organisms. If infested grain is purchased for livestock feed, store it away from the new crop and feed it as soon as possible.

Aeration and Drying. If you begin harvest early with the intention of mechanically drying wet grain, it's important to have a highly reliable aeration system in place, Dorn says. A bin of 19% moisture corn with a starting temperature of 75 F can lose a full market grade in about 5 days if the aeration system shuts down, allowing the grain to heat and deteriorate.

Dorn says stored grain insects cannot live on extremely dry grain (less than 10% moisture), but it's impractical to dry grain below the levels necessary to arrest mold growth (15% in winter or 14% in summer).

"Once grain is dried to safe moisture levels, insect activity in fall-harvested grains can be managed by cooling the grain mass in 10-degree increments when ambient air temperatures allow," Dorn says. "Cooling grain is particularly important in reducing insect reproduction since insects are cold blooded and not active much below 55 F. The eventual goal is to cool grain to about 30 F for winter storage. This will stop both insect and mold activity."

If the grain will be held into the warmer spring and summer months, Dorn says it should be incrementally warmed to 40 F by March, 50 F by May and 60 F in June. Failure to maintain uniform temperatures throughout the bin can result in moisture condensation in the top middle of the bin.

"Check the grain often and run the aeration as necessary to maintain uniform grain temperature," Dorn adds.