Physical control of grain insect pests

High temperature

In the past, grain dryers have been used to help with disinfestation. There are a number of variables that are difficult to manage and may affect end use quality of grain, including temperature, time, and type of dryer. As a result, insect control using high temperature may produce variable results.

A photo of one style of grain dryer
A grain dryer

Caution: After you apply heat treatment, grain must be immediately cooled so that it does not overheat, spoil and cause a new insect infestation. Energy costs for this method of control are high. Therefore, using a grain dryer is recommended only when you need to rapidly dry grain.

Low temperature

Producers and grain handlers can use ambient cold air to prevent and control infestations.

Stored product insect pests generally do not feed or reproduce at temperatures below 18°C. Lower temperatures can also be used to cause mortality. For example, grain kept at -5°C for 12 weeks will control stored insect pests at all life stages.

You can lower the temperature of stored grain by:

  • Mixing and transferring infested grain from one bin or pile to another
  • Transferring part of the crop to a truck or small pile to expose it to low air temperature and leaving it to cool before returning it to the bin
  • Aerating the bin

Aeration systems are very effective at reducing grain temperatures, as well as reducing moisture migration.

Time required at low temperatures to control stored grain insect pest infestations
Constant grain temperature
(°C)
Time period required for disinfestation
(weeks)
-5 12
-10 8
-15 4
-20 1
Chart shows time and temperature effects on insect growth activity or death - details below
Time and temperature effects in relation to insect growth activity or death
Death to insects occurs in minutes
Between approximately plus 50 and plus 60 degrees Celsius or approximately 122 and 140 degrees Fahrenheit.
Death to insects occurs in a day
Between approximately plus 38 and plus 50 degrees Celsius or approximately 104 and 122 degrees Fahrenheit.
Slower growth period for insects
Between approximately plus 35 and plus 38 degrees Celsius or approximately 95 and 104 degrees Fahrenheit.
Maximum growth period for insects
Between approximately plus 25 and plus 35 degrees Celsius or approximately 77 and 95 degrees Fahrenheit.
Slower growth period for insects
Between approximately plus 13 and plus 25 degrees Celsius or approximately 55 and 77 degrees Fahrenheit.
Death to insects occurs in week or months
Between approximately minus 5 and plus 13 degrees Celsius or approximately 23 and 55 degrees Fahrenheit.
Death to insects occurs in days, or months if acclimated
Between approximately minus 15 and minus 5 degrees Celsius or approximately minus 5 and plus 23 degrees Fahrenheit.
Death to insects occurs in minutes
Between approximately minus 25 and minus 15 degrees Celsius or approximately minus 13 and minus 5 degrees Fahrenheit.

Pneumatic conveyer

Cyclone-based grain pneumatic conveyers (also called pneumatic grain auguers or grain vacs) can control insect infestations. The percussion effect created by the cyclone causes insect mortality. The style of pneumatic conveyer and the class and physical condition of the grain may affect this method of insect control. High grain volumes can reduce the effectiveness of this method of control.

A grain vacuator attached to a tractor
A grain vacuator attached to a tractor