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A Few Considerations for Fall and Winter Grain Storage

Originally Submitted: January 11, 2024

Written collaboratively by Adam Varenhorst, Sara Bauder, Philip Rozeboom, Patrick Wagner, and Brad McManus.

With harvest well underway in South Dakota, there is a lot of grain going into storage. Although the critical point during this season is a successful harvest, that success can be diminished if the grain isn’t properly stored. We recommend using the following seven-step integrated pest management (IPM) plan to ensure successful grain storage.

7-Step Stored Grain IPM Plan

Grain storage bin.

Step 1. Structural and Maintenance Components: Keep bins clean and repaired.

  • All season:
    • Keep a 10-foot perimeter around the bin free of vegetation and trash.
    • Clean up grain spills outside of the bin.
  • *Pre-binning:
    • Bins should be built on a moisture-proof base.
    • Confirm that bin facilities are weather-tight and rodent-proof.
    • Screen ventilation openings to prevent entry of rodents and birds.
    • Do not mix new and old grain; remove all old grain from the bin or fumigate old grain.
    • Clean the bin wall, ceiling, ledges, floors, and sills prior to filling with new grain.
    • Clean combines, wagons, grain carts, and trailers prior to handling new grain.
    • Dispose of any debris removed from bins or machinery, as insects may infest it.
    • Examine area to determine if rodent bait stations are necessary.
  • Post-binning:
    • Seal any holes, and caulk around any doors.
    • Do not seal roof aeration exhaust of inlet vents, except during fumigation.

Step 2. Residual insecticide sprays.

  • Pre-binning:
    • Spray the wall surfaces, ledges, floors, and sills with a residual insecticide.
    • Spray outside walls and outside base.
    • For long-term storage (more than 1 year) consider fumigating the area beneath the slotted floor.

Step 3. Condition Grain: Store clean, dry grain.

  • Pre-binning:
    • For long-term storage, corn moisture should be 15% or less.
    • Use a grain cleaner to remove cracked kernels and other debris.

Step 4. Proper aeration.

  • Post-binning:
    • Run the bin fan and stirator to ensure uniform temperatures and prevent moisture buildups. This will reduce mold growth.

Step 5. Use insecticide protectants.

  • Treat grain as it is moved into storage to protect and prevent stored grain insect infestations.
  • For more information on common stored grain pests, see our article Common Stored Grain Insect Pests.

Step 6. Regularly inspect grain.

  • Post-binning:
    • Monitor the grain regularly. For grain above 55 to 60 degrees Fahrenheit, inspect weekly. For grain below 55 degrees Fahrenheit, inspect every two weeks.
    • Use a grain probe to take samples in a pattern from the surface, and from the base of the grain mass.
    • Take samples from the center to the areas near the wall, with samples being no further than 20 feet apart.

Step 7. Treat detected infestations when necessary.

  • If a post-binning insect infestation is detected, consider the following:
    • Move the grain and re-treat as in Step 5. It is possible to kill some of the insects if the grain is moved during cold weather.
    • Feed the grain to livestock.
    • Sell at a reduced price.
    • Fumigate.

*A general rule of thumb is that any pre-binning activities should be completed approximately two weeks before grain will be stored in the bin.

Bin Inspection

Grain bin exterior with ladders installed on the outside.
(Canva photo)

When inspecting stored grain, it is important to remember the potential hazards of grain that is in storage.

For instance, suffocation can occur in grain bins due to bridged grain. Bridged grain occurs when grain mats together and forms a false floor. When the false floor is broken during sampling procedures, cave-ins can occur.

When possible, consider the following safety tips:

  1. Always have another person with a cellphone outside the bin in case there is a problem.
  2. Wear a harness that is attached to a properly secured rope when entering a grain bin.
  3. Use a pole to break up crusted grain from a distance.

    Measuring Grain Temperature and Moisture

    Stored grain with a temperature above 55 to 60 degrees Fahrenheit should be inspected each week, and every two weeks when the temperature is at or below 55 degrees Fahrenheit. Cooling grain reduces the activity of stored grain insect pests and suppresses any mold growth that may otherwise occur. The temperatures required to freeze and kill stored grain pests vary by species, but in general ranges from approximately 23 degrees Fahrenheit to -10 degrees Fahrenheit. Most molds are suppressed at 40 degrees Fahrenheit, except for Penicillium molds, which require temperatures below 32 degrees Fahrenheit. Grain temperature should be measured at several places along the walls of the bin, near the top surface, and within the grain. Temperature sensors are very useful for this, however multiple readings are necessary to get an accurate overall temperature. When using a moisture meter to check grain, be sure to warm up samples to room temperature in a sealed container for several hours before measuring.

    Aerating may cause a small reduction in grain moisture with approximately 0.25% to 0.50% moisture being lost per aeration cycle depending on several factors, such as air temperature and moisture. For long-term storage, multiple aeration cycles may reduce grain moisture by as much as 2%. However, due to low flow rates, the drying front within the bin moves fairly slowly, and most of the moisture reductions will occur in grain that is closest to the entrance of the forced air. Reducing the temperature of grain throughout the bin will also assist with keeping the grain at a cooler temperature through the spring and early summer.

    Winter Storage Tips

    Three grain bins on the edge of a snow-covered field.
    Courtesy: Canva
    • Cover bin aeration fans when not in use. The fans essentially go through the ‘chimney effect,’ where wind moves air into the fan and it travels upwards, affecting the grain inside. Although this can be favorable during cold and dry periods, fans should be covered during snow events.
    • Provide an inlet for air near the roof eave and outlet exhaust near the roof peak to allow warm air to exit the bin (much like the principles of an attic). Several vents at the same elevation can still allow heat to remain at the top of the bin without exhaust at the peak or roof exhaust fans. Without proper ventilation condensation can occur.
    • Monitor grain weekly to detect any changes in temperature, odor, insect pest presence, or mold presence.

    Recommended Airflow Rates

    The following recommendations are from Dr. Ken Hellevang of NDSU Extension.

    • Corn: The fan airflow rate should be at least 1 cubic foot per minute per bushel (abbreviated as cfm/bu) and the initial grain moisture should not exceed 21%. Start the fan when the outdoor temperature averages about 40 degrees Fahrenheit.
    • Soybeans: Use an airflow rate of at least 1 cfm/bu to natural air-dry up to 15 to 16% moisture soybeans. Start the fan when the outdoor temperature averages about 40 degrees Fahrenheit.
    • Wheat: Use an airflow rate of at least 0.75 cfm/bu to natural air-dry up to 17% moisture wheat. Start drying when the outside air temperature averages about 50 degrees Fahrenheit.
    • Sunflowers: Natural air-drying for oil sunflowers requires an airflow rate of 0.75 cfm/bu for up to 15% moisture. The drying should start when outdoor temperatures average about 40 degrees.

    For more information on selecting fans and determining if your fan is large enough, see the University of Minnesota Extensions’ Fan Selection Tool.

    Stored Grain Insect Pests

    Three stored grain pests. From left: Maize weevil, Angoumois grain moth, Cadelle beetle.
    Courtesy: Gary Alpert, Harvard University; Clemson University-USDA Cooperative Extension

    If you do detect an infestation and are considering using a fumigant insecticide product, we strongly recommend hiring a professional, as these products are highly toxic. Fumigants should not be applied in the winter, as these products require warm temperatures and humidity to properly work. The product labels will have tables that list temperatures and humidity levels that are unacceptable for use. For more information on common pests to look out for, see our article Common Stored Grain Insect Pests.