Grain Mites in Stored Foods

By Chris Williams on October 17, 2011.

Q. Can you explain to me what a grain mite is? Can you see it? Does it bite?

A. Grain mites are just one of several different species of mites that can infest stored food products. These tiny mites feed on a range of food materials ranging from grain, flour, and cereals to dried fruit, sugar, and dry pet food. The group of food mites are sometimes called acarid mites and includes the grain mite, the cheese mite, the mold mite, and others. They pretty much have one thing in common though. They all feed on foods that are damp, and even moldy. The mites feed on both the food material and on mold growing on the food material.

These mites are very difficult to see; they are almost microscopic. Since they are usually noticed only in large numbers, what you see looks like a pile of brown powder…but the pile, made up of hundreds of mites, moves in waves! If you were to look closer, under magnification, you would see that this mite dust is made up of live mites, dead mites, shed skins, and feces. The food material that the mites are in may actually “sweat.” The mite itself has a sweet, minty smell when crushed and imparts that smell to the food. However, infested food has an “off” taste due to mold spores spread by the mites.

miteGrain mites are probably the most common of the food mites. They are more of a problem in commercial food production where they can become a serious pest in stored bulk grain, or in bakeries or stores where foods are stored and sold in bulk. The mites can be a problem in home kitchens if humidity is high and foods have been allowed to become damp or moldy. Grain mites require a relative humidity of at least 60%; they prefer 75-85%.

In unusual situations, grain mites are not found in stored food at all, but can be infesting bird and rodent nests, hay or straw, hair-filled upholstery, bee hives, insect collections, and moldy paper. Again, always in a damp situation.

Grain mites don’t bite. They can cause diarrhea if accidentally swallowed, or allergic reactions, asthma, or itching in some people. “Grocer’s itch” is a temporary skin condition caused by skin contact with grain mites.

The key to getting rid of grain mites is to first find and discard all infested foods. Because mites and their eggs can be packed into tiny cracks, a thorough cleaning and an insecticide treatment of shelves are probably necessary to get control. Reducing the humidity and discarding old products will help prevent future infestations. Give Colonial a call. We do pests so you don’t have to!



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