By Kim Stonehouse, MSc, PAg, Crops Extension Specialist, Tisdale
February 2025
Reports are already coming in about insects in stored grain. This is much earlier than usual and may be a result of retained field heat and moisture migration within bins. Regular monitoring of stored grain for insects is always important and can alleviate a lot of problems when delivering to the elevator. The Canada Grain Act has a zero-tolerance policy for any insects that feed on whole, sound grain delivered to elevators.
The most sensitive way to detect insects in stored grain is by using a probe trap. The trap should be placed in the top centre of the bin because this is where the first signs of a problem usually occur.
Insects found in stored grain feed on the grain or on fungus that may be developing within the grain.
Grain-feeding insects include the rusty grain beetle, red flour beetle and saw-toothed grain beetle. The rusty grain beetle is the most common insect found feeding on stored grain in Canada, and heavy infestations can cause the grain to heat and spoil. These beetles are cold-hardy and can survive temperatures below zero.
Fungus feeders include foreign grain beetle, grain mites and psocids (book lice). The foreign grain beetle will also feed on grain if the moisture content is at the high end of the acceptable range. Insects that feed on fungus cannot survive on dry grain.
There are methods that can be used to control both grain and fungus feeders. Mechanical methods tend to be the most economical and do not require any special licensing. Many of the above noted insects can be killed by reducing the core grain temperature for a period of time with aeration or moving the grain several times mid-winter. Other mechanical control methods include moving grain using a pneumatic conveyor, such as a grain vac, at low transfer rates or passing the grain through a heated grain dryer for a length of time.
In warmer conditions, treatment options for grain being rotated to a clean bin include diatomaceous earth, malathion and phostoxin. It is important to note that oilseed crops, including canola and flax, should not be stored in bins treated with any of these products. For malt barley or milling oats check with your grain buyer before using malathion or phostoxin.
Identification of the pest to be controlled is important for the determination of the correct control product to be used. For example, the flat grain beetle can look similar to the rusty grain beetle, but the products registered to control it may not be the same.
Always read the product label to ensure that it is registered for use in the grain to be treated and on the insect to be controlled. Follow label instructions for effective and safe application. With some products, the use and sale are restricted to licensed pesticide applicators with a valid fumigation licence.
For more information on preventing and controlling insects in stored grain, please refer to Insects and Mould in Stored Grain. As well, you can contact the Agriculture Knowledge Centre or your local crops extension specialist.