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The Foreign Grain Beetle is Actually a Mold Pest

By Chris Williams on December 5, 2014.

mold eating pest foreign grain beetleWhen homes have a mold problem, they often also have infestations of insects that feed on mold. Mold-feeding insects range from booklice (psocids), to springtails, to various fungus beetles. One of the most common fungus beetles is the foreign grain beetle. It’s always difficult to explain to customers that, despite its name, this is indeed the beetle that is flying around their upstairs bedroom where there has been a roof leak.

It’s Also a New Construction Pest

Foreign grain beetles get their name because they are commonly found in moldy grain in storage. But they are feeding on the surface mold, not on the grain itself. The beetles are not limited to mold on grain or foods; they are found in many other situations where mold is growing on damp surfaces. Don’t expect to find a green mold growing on the surface of materials. Surface mold may be a very thin, whitish film that is barely visible.

These tiny beetles can be major pests in new construction where building materials such as lumber and drywall remain damp for some time (see Renovation Brings Fungus Beetle Problem). Foreign grain beetles are strong fliers and often are first noticed when they emerge from damp wall voids, flying towards light in living areas.

Foreign grain beetles are very tiny, only about 1/8 inch long, and dark in color. They look very much like other beetles that are stored food pests such as flour beetles or sawtoothed grain beetles. You would need magnification or an expert to tell them apart. In a kitchen, you could find foreign grain beetles feeding in food products that are old, damp, and moldy. Check packages at the back of the shelf that are past their “Use by” date.

To Kill the Beetles, Kill the Mold

If you suspect that you have foreign grain beetles, or other fungus beetles, in your home but not in the kitchen, you probably need to correct a moisture problem. The moisture problem could be from a roof leak, leaky windows or skylights, a plumbing leak, unseasoned wood or other damp building materials, or just from excess condensation.

Fungus beetle problems can be seasonal, building up in warm, humid weather and dropping off naturally during periods of cooler, drier weather. In new construction, the beetles disappear eventually as the house or other structure gradually gets too dry to support fungus growth. You can speed up the drying process by increasing air circulation, using fans, heaters, and dehumidifiers.

The good news is if you can find the source of the excess moisture and can repair or dry out the area, you’ve also solved your beetle problem.

When the moldy area is dried out, the mold dies and the beetles will die or leave the area. If you need help finding the source of the mold and the beetles, give Colonial a call. We’ll send a trained inspector out right away. We do pests so you don’t have to!

Photo: CSIRO [CC-BY-3.0], via Wikimedia Commons

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