Lack of rainfall has put many corn producers in a bind, forcing them to begin harvest before the normal time. Early storage results in more days of warm, moist air before we reach the relatively secure air temperatures of 50o F or lower. This early harvest is compounded because the kernels are often still at very high moisture levels. Early binning corn with 15% moisture or greater is a real gamble. As one’s storage capacity gets larger, the gamble is greater and may cost the producer more than the value of the corn.
The optimum moisture content for stored grain is 12 to 13%. Most grain-4 inhabiting insects require 13 to15% moisture for maximum feeding and reproduction. In addition to insect problems, high moisture content can result in spoilage and fungal problems.
Before the Corn is Binned
- Bin preparation should occur at least 2 weeks ahead of binning.
- All old / leftover grain and associated dust and trash should be removed from the bin.
- Insure that your storage provides sound protection from the outside. Patch, caulk or otherwise cover places in bin walls, joints, and roof that will allow the entrance of water and insects. A ¼-inch hole might seem small to you, but it is a mega-tunnel to insects crawling up the outside bin wall.
- Clear spilled grain, weeds, and other organic matter from around the exterior of bins, including pits, conveyers, and legs.
- Fumigate under the perforated floor and / or ducts.
- Treat the inside of the bin with an approved dust or liquid insecticide. Labels for these products have recently changed, so be sure that you are making a proper application.
- Treat around the exterior of the bins with an approved insecticide.
- Inspect and clean every piece of equipment that is used to haul / transfer grain. For example, combine, grain wagons, truck beds, pits, augers and belts, and legs.
- Beyond grain moisture and temperature, thorough sanitation is the single most important preventative control practice. Neglecting to do this can result in your “seeding” your grain stream with insect pests.
- These products are quite expensive.
- If using a grain drier, remember to apply the protectant AFTER the grain has cooled. Applying to hot grain will cause the product to deteriorate.
- This cost can be reduced by applying the treatment to only the first and last load.
- Some storage managers will treat grain with a grain protectant. Although this is more common in wheat than in corn (there are no protectants for soybean), with good management, and if you are only holding through the fall, winter and spring, this is probably not needed.
- Fumigation under perforated floors and in duct systems can be extremely helpful but is quite dangerous and should be completed by trained professionals.
- Considerable specialized training, equipment and supplies are required to perform a safe and effective fumigation, not to mention extensive record keeping.
- If your fumigation is not done properly, it will not reach the areas of need and you will have accomplished nothing, all at a relatively large expense.
After the Corn is Binned
Move air through the corn any time you can. Reducing the grain temperature has a direct effect on the growth of insect populations. This is why we have more troubles in wheat than in corn. Even in a hot Kentucky summer, there are times when outside air is cooler than the grain mass. I strongly recommend the use of automatic fan controllers. Information on these devices can be found on the University of Kentucky BioSystems and Agricultural Engineering Web site or from Dr. Sam McNeill of that department.
In Kentucky we sometimes have problems with moth pests in addition to the beetles. The caterpillar (young stage) of these pests is the important stage, and is restricted to the grain surface.
- A “cap out” treatment; applying a layer of one of several products to the top 4 inches of the grain will provide a barrier. Products containing Bacillus thuringensis (Bt) are commonly used for this.
- Deployment of “Insect Shield Strips” in the void above the grain mass may provide control of various grain moths before they can lay their eggs.
Regular checking of your stored grain for insect and storage problems can be of great value. For grain spoilage and for surface infesting caterpillars (for example, Indian meal moth) simply looking in the hatch and using your nose to smell the grain can be of major value. Additionally, pheromone baited traps can be used to capture the moth (adult) stage of the caterpillar pests to provide advanced warning. Pitfall traps are a relatively simple way to detect the presence of stored grain beetles within the grain mass. This takes a little practice, but will be increasingly more useful as one gains experience with them. Though we do not have definitive thresholds for these measures, they will tell you when the insects are present and, by taking samples through time, how the population is changing. After one has used these techniques for several years, they may also provide a measure of increasing or decreasing risk of insect damage.
For fumigants and insecticides that may be used in stored corn, please see Insecticides Recommendations for Corn-2014 (ENT-47) available online or from your county Cooperative Extension Service office
“If you can only do one thing, store clean dry grain in clean dry bins!”
By Doug Johnson, Extension Entomologist, University of Kentucky