Farm-stored corn insect management

Robert  G. Bellinger 

Farm-stored grain quality is at its peak when it is loaded into the bin for storage. After loading the best you can do is to try to maintain this level of quality. Therefore, it is important to maximize the quality of your corn prior to storage. At harvest make sure that your corn is dry enough for storage. The longer it will be stored they drier it will need to be. Adjust your harvesting equipment to minimize breaking kernels.

Only load corn into a thoroughly cleaned, empty bin. Don't load grains on top of older grains! When loading corn into the storage bin make sure your loading auger and mechanical spreaders in the bin are in good condition and will not damage the corn when loading. Run the auger at full capacity (run at a slow speed) to minimize breaking the kernels. The cleaner and drier the corn going into the bin, the better.

Do not overfill the bin. Level the corn in the bin as soon as it is filled and immediately begin aeration to cool the corn. Poorly controlled temperatures are the most important cause of stored all stored grains, including corn, going out of condition. Get the corn cooled down to the outside air temperature as soon as possible. Keep the bin temperature no more than 10 - 15^oF of the outside temperature during storage. Ideally the temperature should be maintained at 35 - 40^oF.

Proper harvest, loading and storage of corn is critical for managing potential insect infestations. Proper storage management provides the best control for the cost. It is important in any insect management system to not rely solely on insecticides. This is particularly true for stored grains; there are few insecticides registered in this use area, and fewer still for the individual stored commodities. Also, insecticide resistance has already made at least malathion essentially useless in many stored grains environments. Malathion is not recommended on stored corn (see notes below.)

Insects will stop feeding and reproduction at temperatures below about 50^oF. Because corn is harvested when temperatures can still be fairly warm, immediate aeration to get harvested corn to ambient temperature is critical to help prevent insect infestations. Even corn held at the moisture levels that will not allow mold growth, properly cooled and dried corn can still be infested by at least Indian meal moth. This moth infests the grain from the top of the bin. The adult moth can be controlled using DDVP (dicholorvos) resin strips in the head space of the bin, using 1 strip per 1,000 cubic feet (controls adults only). Change strips at least monthly in warm weather. You may alternatively, or also, use a Bacillus thuringiensis (Bt) product (for example, Dipel) as a top dressing (grain surface treatment) applied immediately after bin loading to control larvae. Diatomaceous earth products may also be use here but monthly treatments will be needed.

Properly loaded corn should be stored in thoroughly cleaned and surface-treated bins (bin surface treatment).  A grain protectant (Atellic only) can also be used when loading the corn. However, even if both of these procedures are followed, you must stillregularly check the corn - check storage temperature and moisture levels and for flying moths, and surface crusting.

These recommendations are based on active ingredients. These recommendations are not a substitute for carefully reading the pesticide label. Other registered products not mentioned here may be as effective.

Note: Product use sites - Read the label carefully! Use sites vary widely from product to product. Some products may only be used to treat grain storage bin surfaces and not grain; few products may be used for both applications. Grains that may be treated vary with product.

Note: Product rates - Read product labels carefully! Rates vary with formulation of product used, use site/crop being stored, anticipated storage time, and pest species, and pest development stage. Some products may only have one (1) application made to a load. Period of control can vary with pest insect species and is shortest at the lowest rates.

Note: Pests controlled - Read the label. Not all products control all pests, especially at the lowest rates. Bacillus thuringiensis (Bt) products control only caterpillars (moth larvae), and not beetle grubs. Control will be slow.

Note: Formulations - Read the label. Choose the correct formulation. Be sure you have the necessary application and safety equipment and PPE to make an application with the product formulation you consider. Some formulations may not be applied directly to grain. Some products may be applied with water or food-grade oil or soybean oil, usually except for peanuts.

Note: Insecto (a diatomaceous earth product) - "Insecto Control Plan" calls for dusting the empty bin, treating the bottom 2 feet of grain, treating the top 2 feet of grain, top-dressing leveled grain with this product at labeled rates. Inspect grain bi-weekly. Organic Materials Review Institute (OMRI) Listed.

Note: Actellic 5E - only one (1) application method is allowed per load. Only one (1) application allowed per load.

Note: Diacon II (s-methoprene) - Insect growth regulator controlling larvae only. Lowest rates give control for less than 6 months. May be applied with water or food-grade oil or soybean oil, except for peanuts. Product may be applied with an insecticide controlling adults. Read the label(s).

Note: Fumigants are the most effective way of controlling insect infestations in stored grain; however, fumigants provide no residual control. Fumigants are Restricted Use Pesticides (RUPs) and may be purchased and used only by licensed applicators. These pesticides are Danger, Danger/Poison labeled because of acute toxicity. Fumigants have strict application requirements via the label and applicator manual. Product-specific training and/or product company supervision may be required, especially for liquid and gas formulations.

Note: Malathion is not recommended because of pest resistance in international market issues.

Grain Bin Surface Areas and Capacities

Page maintained by: Pawel Wiatrak, pwiatra@clemson.edu