What kinds of insects infest stored grains?
What are the steps to follow before putting grain into a bin?
What are the steps to consider during bin filling?
What more can be done after binning is complete?
What should be considered in ongoing management of stored grains?
How can temperature help rid stored grain of insect pests?
A pictorial key to beetle pests commonly found in stored grains? 

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What kinds of insects infest stored grains?

Several different kinds of insects may infest stored grains.  With beetles it is the larval and the adult stage that do the damage.  Certain moths are also known to infest stored grains; however, it is only the larval stage that is damaging.   

The above insects are classified as one of the following:

• Internal feeders - feed within grain kernels
• External feeders - feed without entering the kernel
• Fungus feeders - feed on moulds and fungi associated with damp grains

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What are the steps to follow before putting grain into a bin? 

Newly harvested grain may become contaminated when placed in contact with old infested grains.  Ensure that all machinery, augers, storage facilities, aeration systems, and storage areas are cleaned prior to handling new grain and placing it in storage.  The following checklist may be helpful:

• Brush, clean, sweep, and/or vacuum grain harvesting machinery (i.e. combines, augers, trucks, bin sweeps, etc.)
• Sweep and clean empty bins of all infested grains and dust.  Treating bins with diatomaceous earth or Malathion (except in oilseeds¹) is recommended.
• Remove remnants of grains from aeration systems, ducts, and exhaust systems.
• Clean areas surrounding storage sites that might house insects in various stages of development.  Reduce or remove vegetation within 10 metres of the storage sites.
• If newly harvested grain is to be placed in storage with previously stored grains, ensure that the old grain is clean.  Consider fumigation prior to placement of the new grain.  Note that mites in the hypopus stage may be resistant to fumigation. 

¹ Canola Council of Canada warns not to use Malathion to treat canola or bins where canola will be stored.

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What are the steps to consider during bin filling? 

Grain is often harvested and moved to storage under high temperatures.  Aeration can be used to lower the stored grain temperatures to 10° C or lower, reducing insect activity. 

If grain is to be stored for longer periods of time, consider adding a “grain protectant” to enhance insect control.  Grain protectant works as insects crawl through treated grains.  These products are generally applied to grains as they are being augured, loaded, or turned into storage facilities. 

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What more can be done after binning is complete? 

Consider applying grain protectant as a top dressing to grains already placed in bins.  These products may be raked into the surface layers of stored grains to reduce infestations from surface feeders that could infest stored grains.  Be careful not to exceed registered dosages of grain protectant if the grain has already been treated during storage. 

For grains stored above 10° C, monitor every two weeks for insect activity and temperature changes.  Use a grain probe to check for insects within the grain mass - not just the surface.  Proper insect identification will help determine what control measures may be necessary. 

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What should be considered in ongoing management of stored grains? 

Regular monitoring and proper treatment when required is essential to ensure marketability of grains.  There is a zero tolerance for insects in stored grains delivered to the market.

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How can temperature help rid stored grain of insect pests? 

Temperature control is a means to deal with insect infestations in stored grains.  Grain stored at the proper moisture content and temperature is less likely to be infested by insects.  Extremes in temperature will kill insects that are exposed to such conditions over time.  For instance, reducing the grain temperature to below 0° C or colder will kill insects over time:

• -5° C → insects die in eight weeks
• -10°C→ insects die in six weeks
• -15°C→ insects die in four weeks 

High temperatures will also kill insects in relatively shorter time periods than cold temperatures as shown below:

• +40° C→ insects die in one day
• +50° C→ insects die within minutes 

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To download a pictorial guide to beetle pests click the image link to the left. (PDF 76KB)   Problems printing PDF files from Adobe Acrobat Reader?

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References: 

Winnipeg Cereal Research Centre:
http://res2.agr.ca/winnipeg/storage/pages/princ_e.htm 

Stored Food and Grain, Department of Entomology, Perdue University, USA:
http://www.entm.purdue.edu/Entomology/ext/targets/e-series/EseriesPDF/E-66.htm 

Saskatchewan Agriculture and Food:
FAQ - Grain Storage Considerations

FAQ - Grain Drying

Acknowledgements 

Dale Risula, PAg, SAF, Integrated Cropping Management Systems Specialist
Scott Hartley, PAg, SAF, Provincial Specialist Insect/Pest Management
Grant McLean, PAg, SAF, Crop Management Specialist
Dr. Patrick Mooleki, SAF, Crop Development Specialist
Ralph Howes, PAg, SAF, Production Economics Specialist
Some photos courtesy of the Cereal Research Centre, Agriculture and Agri-Food Canada.