By: Kaeley Kindrachuk, AT, Regional Crops Specialist, Outlook
Regular monitoring of grain for insects is important in predicting potential problems and preventing serious infestations. The Canada Grains Act has a zero tolerance policy for any primary insect (insects that feed on grain, not fungus feeders or incidental insects) in grain delivered to elevators. The best way to keep insects out of bins is to have a clean and well-sealed bin. This will help eliminate any initial infestations, but infestations can still occur if grain is stored for long periods of time. It is important to remove cracked grain and other residues that insects could feed on. Equipment used to move grain and the area around bins should also be kept clean, as insects can be found in grassy areas and on spilled grain.
Correct identification of insects is key to determining which control method should be used. Some insects will feed on grain and others on fungus. 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. Red flour beetles prefer grain dust and broken grain, and can be controlled by moving grain whether it is cold or not. The saw-toothed grain beetle is more common in stored oats than wheat or barley. Fungus-feeding insects include foreign grain beetles, grain mites and psocids. Foreign grain beetles resemble the rusty grain beetle but have a club-shaped antennae, and, while they prefer fungus, will feed on grain when the moisture content is at the high end of the acceptable range. Grain mites are very hard to see (0.2 to 0.5 mm long) and psocids are 1 mm in length and have long antennae. All fungus feeders can be controlled by drying the grain.
In warmer conditions, treatment options include Protect-It or Insecto (which are Diatomaceous Earth), Malathion Grain Protectant Dust, and Tempo 20 WP. Oilseed crops, including canola, flax and sunflowers, should not be stored in bins treated with Malathion or Tempo. Always read the product label to ensure the product being used is registered for the grain and will be applied effectively and safely (information can be found on page 663 of the 2017 Guide to Crop Protection). The effectiveness of diatomaceous earth and Malathion Grain Protectant Dust will be limited when insects are not active and application is probably not economical. Phostoxin is also registered but can only be applied by licensed pesticide applicators with a valid fumigation licence and should not be used in temperatures below 5 C. If phostoxin is applied in temperatures below 5 C, the gas will not be released until the temperature warms up.
For long-term storage, the grain temperature should be lowered to below 15 C as soon as possible after the grain is placed in storage. Below this temperature, reproduction and movement of insects is reduced. Grain that is not moved or aerated after harvest can remain warm enough to allow insects to survive the winter. Rusty grain beetles and other stored grain insects can be killed by reducing the core grain temperature to -5 C for 12 weeks, -10 C for eight weeks, -15 C for four weeks or -20 C for one week.
For more information, check out our factsheet on insects and mould in stored grain or the Canadian Grain Commission's photo identification keys to insects in stored grain.