August 27, 2010

Despite the spring rains which delayed planting, it appears corn and soybeans are on track for a normal harvest date this year. Grain producers should be preparing bins and equipment now to avoid problems at harvest.

Grain harvested in Nebraska is essentially free of insects, but can become infested by storage insects, which originate in or around the bin or in contaminated equipment.

Clean Bins and Equipment

The first goal should be to store sound, clean, dry grain. Storage insects often get started in the grain dust and broken kernels and fines which tend to concentrate right under the loading auger in the center of the bin. Fines also restrict airflow through the grain mass and make it harder to uniformly dry the grain and regulate temperature with aeration.

• If possible, screen out broken kernels, trash and fines to increase the quality of the final storage product. If screening is not possible, consider overfilling round bins and then removing a load or two of grain with the center unloading auger to pull some of the fines out of the center of the bin. This also has the advantage of leaving the grain surface nearly level.
   
• Since stored grain insects can invade new grain from infested harvesting and handling equipment (combines, augers, etc.), it's essential that this equipment and any bins be well cleaned before harvest. 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.
   
• 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 shop vacuum are essential pieces of equipment in cleaning grain bins.
   
• 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.

Maintain Bin Foundation, Lanes

Grain bins require a solid foundation to bear the weight. A 9,000 bushel bin is supporting over half a million pounds of grain besides the weight of the bin itself and the concrete pad. Be sure to remove old equipment, junk, 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.

You can't 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 when the soil is wet.

Dry and Cool Stored Grain

If you begin harvest early with the intention of mechanically drying wet grain, it is important to have a highly reliable aeration system in place. 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 heats up to heat and deteriorate.

Check for Rodent and Weather Damage

Mice often nest in control boxes where they are protected from predators. They can strip insulation from wires for nest material and their urine can corrode 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, 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.

Control Conditions that Benefit Grain Storage Insects

Stored grain insects cannot live on extremely dry grain (less than 10% moisture), but it is impractical to dry grain below the levels necessary to arrest mold growth (15% in winter or 14% if held into summer). Once grain is dried to safe moisture levels, insect activity in fall-harvested, stored grains can be managed by cooling the grain mass in10°F increments whenever ambient air temperatures allow.

Cooling grain is particularly important in reducing insect reproduction since insects are cold blooded and not active much below 50°F. The eventual goal is to cool grain to about 30°F for winter storage which stops both insect and mold activity. If the grain will be held into the warmer spring and summer months, it should be incrementally warmed to 40°F by March, 50°F by May, and 60°F by 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 fans as necessary to maintain uniform grain temperature throughout the bin.

Apply Insecticides

If you think there is any chance you might hold grain in the bin into May or later, it would be prudent to apply residual insecticides to the empty bin after thoroughly cleaning it. The list of insecticides registered with the Nebraska Department of Agriculture for use in grain bins is available on the UNL Grain Storage Management web page http://lancaster.unl.edu/ag/Crops/storage.shtml#Pest. This list is automatically updated by the NDA. The UNL Department of Entomology also offers information on this topic.

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.

Tom Dorn
Extension Educator, Lancaster County