Blog: The Wheat Sheaf

Stored Grain Insect Management during a Canadian Prairie Winter

Having grain rejected by an elevator manager due to the discovery of insect pests is troublesome and can be expensive and difficult to market the commodity.

Pictured left: Rusty Grain Beetle 

Courtesy of the Canadian Grain Commission

Stored grain insect pests such as the Rusty Grain Beetle and many others can attack grain right from harvest and throughout the early fall. They are attracted to the grain by the volatiles that the grain gives off as the grain respires. Once within a grain mass of 20°C or higher, the insects can feed, find mates and reproduce. Within 60 days of harvest, if temperatures are appropriate (grain temp between 18°C and 40°C), populations of insects such as the Rusty Grain Beetle will explode as the females lay hundreds of eggs and their life cycle to reproduction is only about 21 days. 

Preventive measures such as cleaning bins (including below aeration floors) and treating the interior bin walls and around access points such as vents and doors is a good first step. When harvest is warm (when the day:night temps are greater than 20°C:10°C) consider adding malathion or diatomaceous earth to cause mortality of any insects that may have accessed the grain. Then, after initial storage, consider aeration to get the bin temperature of the grain

below 15°C which will stop any insects that have managed to access the grain from feeding and reproducing.

Pictured right: Rusty Grain Beetle Courtesy of the Canadian Grain Commission

In the event grain has been rejected at an elevator for the presence of insects, it will require bringing it back to the farm to manage the issue. Request to know what the insect pest’s identity is and have the specimen’s identity confirmed though contacting your local Provincial entomologist, university entomology department or staff at the Canadian Grain Commission as this can assist in determining the best reactive measures to implement.

If fumigation is considered, then consider tarping off the grain in the bin and ensure leakage is mitigated. While aluminum phosphide labels state the product can be effective above 5°C, the evolution of the gas can take too long to allow for the appropriate concentration to be gained. Proper sealing of bins to determine their ability to be successful for fumigation should be performed prior to storage. Follow label instructions for application techniques and safety precautions.

Aeration to control insects can be achieved, but it takes a great deal of time and energy to change a grain bulk’s temperature. If a grain mass can be brought to below -10°C, it will take about 2 months to cause insect mortality, 1 month at -15°C and less than a week if the grain temperature can be brought to -20°C. It is very important to consider levelling grain masses prior to aeration as peaks in masses will capture moisture and heat and this could continue or increase the problem.

Grain vacuators can cause insect mortality, but the key feature is to not move too much grain at once through the vacuator to allow for as much percussion of the kernels in the cyclone to occur as possible.

For further information on this topic, please contact the Grain Sanitation department at the Canadian Grain Commission at: 204 983-2788.

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