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ISSUE 16    August 18, 2005


Grain insect pests can cause economic damage to stored grains by reducing weight, nutritional value, and germination. Infestations also cause contamination, odor, mold and heat problems that reduce the quality of the grain and may make it unfit for processing into food for humans or animals. Producers may receive a reduced price for contaminated grain or it may be completely rejected by commercial grain buyers.

Preventative Measures before Binning Grain: Newly harvested grain may become infested with grain insects by contacting previously infested grain in combines, truck beds, wagons, augers, bucket lifts, grain dumps, and other grain-handling equipments, or old grain already in the bin. Insects can also crawl or fly into grains bins from old contaminated grains/debris. Use the following guidelines about two-three weeks before grain is placed in the bins to prevent severe insect infestations.

  1. Clean any grain-handling equipment by vacuuming or sweeping to remove any insect-infested grain or debris.
  2. In empty bins, thoroughly remove any debris by vacuuming or sweeping walls, ceilings, ledges, rafters, braces, and even remove debris from fans, exhaust and aeration ducts beneath slotted floors, when possible.
  3. Remove all old grains or debris from storage site. This old debris contains insect eggs, larvae, pupae and adults, which are ready to infest the new grain!
  4. Remove debris and vegetation growing within 10 feet of bins or storage area. Spray with an herbicide to remove any weedy plants, which may harbor insects.
  5. Spray inside and outside of bin with a residual insecticide to the point of runoff: malathion, methoxychlor, storicide, storicide II, tempo, reldan, or diacon II (This is an insect growth regulator, which prevents the larvae from developing into adults. Adult insects are not controlled.). Be sure to spray the soil around the bins and outside walls, especially cracks, doors and fans.
  6. If newly harvested grain is added to old grain already in storage. It is a good idea to retreated old grain with grain protectant or fumigate. Fumigation must be applied by certified pesticide applicators only.

Preventative Measures during Binning: If grain is to be stored for one year or more, it is a good idea to apply a grain protectant. Grain protectants are insecticides registered for application to whole grain to protect against insect infestation while the grain is in storage. Grain protectants kill insects as they crawl about or feed on treated grain and/or grain fragments. These formulations are generally applied to grain as it is being augured, loaded, or turned into storage facilities.

Registered grain protectants in North Dakota include: corn/sorghum - acetellic 5E; wheat, barley, oats, sorghum, corn - diacon II, malathion, reldan (product is being phased outs, not for corn), storicide, and storicide II. Grain drying in bins during high temperatures will reduce the residue of insecticide due to rapid volatilization. Residue is also reduced when applied to grain with higher moisture. Always read and follow label directions when applying any insecticide.

Preventative Measures after Binning: A surface treatment can be applied to "top dress" or "cap off" the grain already in storage. This protects the grain mass from surface feeding insects, such as the Indian meal moth. It is recommended to remove any crusting or webbing first and then to rake insecticide into top few inches of grains to increase the efficiency of the insecticide. Two insecticide products registered in North Dakota are dipel (Bacillus thuringienesis) and Insecto (diatomaceous earth). No-pest strips (dichlorvous impregnated strips, DDVP) can also be hung from the ceiling of grain bin during spring, summer and fall to deter any flying insects. Suspend one strip per 1,000 cubic feet of air space. These strips may need to be replaced every three months, especially during summer months.

Remember to monitor grains in bins for insect activity every two weeks when temperatures are above 55F. Stored grain insect pests are generally inactive at temperatures below 55F. If you find any insects, be sure to properly identify it. Knowing what insect species is infesting stored grain can provide important information on the grain condition and what the best curative or preventative action is. In short, stored grain insects can be thought of as very expensive, unwanted, tiny livestock!

Janet Knodel
Area Extension Specialist
North Central Regional Extension Center

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