Preventing Stored Grain Insects

A reminder before moving and storing new grain to clean old grain out of bins, augers, combines, truck beds, and other areas where grain or grain debris may be. Infestations of stored grain insects such as rusty grain beetles do not get started by harvesting the insects along with the grain. They are the result of insects already being present in bins or equipment used to move grain, or insects being able to get into the stored grain through openings in bins or storage structures.

In Figure 1 below, there is a picture of a sawtoothed grain beetle (top right), red flour beetle (bottom left), and rusty grain beetle (bottom right) with a grain of wheat (top left) to give perspective on size.


Figure 1. Some beetles that may occur in stored grain.

Some insects in stored grain, such as the rusty grain beetle, will feed primarily on the grain, while others, such as foreign grain beetle, may be feeding primarily on molds growing on grain that is too moist. So it is good to know the species you are dealing with as management options may differ. Although both are very small beetles, when placed in a glass jar foreign grain beetles can climb up the sides, while rusty grain beetles cannot.
For long-term storage of grain, lowering the grain temperature below 15C as soon as possible after the grain is placed in storage can help minimize the risk of stored grain insects. Below 15C potential insect pests of stored grain stop laying eggs and development stops. Grain that is not aerated or moved after harvest can often remain warm enough for insects to survive the winter.
The above information was submitted by John Gavloski, MAFRD Entomologist.  It is available in the last issue of the Manitoba Insect and Disease Update which is posted at:
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