Stored Grain Insects, Mites and Molds - Frequently Asked Questions

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 What can I do to prevent my crop from infestation by stored grain insects?
The best time to minimize the potential for stored grain insects is before the grain is in the bin. A thorough cleaning of the bin prior to filling is the best method to reduce any small populations of stored grain insects that may become a problem later in the year. Storage bins, especially if there’s a history of infestation, can be sprayed or dusted with a recommended insecticide before grain storage.

Producers can help prevent problems by cleaning up any spilled grain around the bin. Spilt grain, exposed to environmental moisture, can easily build up populations of insects that could migrate into the bin later in the year. Cleaning up and removing any outside grain can minimize future problems within the bins.

Preventing Insect Infestations

What conditions would make stored product more susceptible to stored grain damage?
Warm, moist or weedy crops would be most susceptible to damage. Warm or moist grain will contribute to moisture migration within a bin. These conditions can cause locations within the bin where grain will spoil and result in insect infestation, mite and mold development. In fall the outside of the bin cools quickly. The cool air settles, while the warmer air, located in the interior rises, causing a circular flow within the bin. This air pattern deposits moisture, through condensation, at the top center of the bin. In spring the reverse occurs, where warming from the sun warms the outside layer, causing a circular air movement depositing moisture at the bottom of the bin. Moulds that develop give off additional heat and moisture, resulting in a microclimate more favorable for stored grain insect populations. Mold byproducts can be toxic if fed to farm animals. The more moisture in the grain, the more likely it is to have a zone with enough moisture to start a stored grain insect problem if the pests are present.
Weed seeds, which often have higher moisture content than the harvested crop, can be concentrated in the central core as the grain when binned. This situation can cause more moisture to buildup in this area. If the stored grain is particularly weedy and/or moist, cleaning or drying the grain may reduce insect problems in storage at a later date.

Grain Storage

How do I identify the pest?
The most common and serious insect pest is the Rusty Grain Beetle. Large populations can cause grain to heat and spoil. Look for a distinct emergence hole in the germ area of the seed. The Red Flour beetle is another common pest, but it cannot feed on undamaged dry seed with less that 12% moisture. Saw-toothed grain beetles occur most commonly in oats. These beetles can be confused with other beetles that feed on fungus, including the foreign grain beetle. Grain mites are whitish and very small(.2-.5 mm).

Primary Insect Pests of Stored Grain
Secondary Insect Pests of Stored Grain

Can I protect the grain in the bin if stored grain insects are a risk?
If a stored grain insect problem is anticipated, products can be added while augering or moving grain. Products with diatomaceous earth such as Protect-It® can keep potential insect problems in check. Addition of these products at recommended rates while augering grain will provide protection against stored grain pests. Call the Ag-Info Centre for more information 310-FARM (3276).

What if stored grain insect problems develop?
If a problem is determined, a producer can move grain in cold weather (minus 20 Celsius or colder). Moving the grain cools and dries the grain and insects, reducing populations and dispersing any warm or moist grain pockets. Pneumatic conveyors (grain vacs) will kill most free-living insects, especially fungus feeding insects and mites. Incorporating diatomaceous earth products while rebinning can also help minimize stored grain pest buildup.

Fumigation with a chemical such as Phostoxin® is also possible at this stage. This is a Restricted product and use can only be performed by a licensed applicator.
No matter what chemical is used, always follow label directions and Restrictions on Sales and Wait periods before sale.

Prepared by Jim Broatch, Ag-Info Centre, Alberta Agriculture and Rural Development

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For more information about the content of this document, contact Mark Cutts.
This document is maintained by Mary Ann Nelson.
This information published to the web on October 15, 2003.
Last Reviewed/Revised on April 29, 2015.