Fact Sheets - Flour Beetles
Pest Management Fact Sheet #5021
James F. Dill, Pest Management Specialist
Clay A. Kirby, Insect Diagnostician
Description & Biology
Common flour beetles found in Maine include the confused flour beetle and the red flour beetle. They are similar in habits and appearance. Both beetles primarily infest flour and, to a small extent, foods made of processed grains. Confused flour beetles and red flour beetles are often found together. Even though they cannot attack whole grains, there are usually enough broken kernels and grain dust, caused by the rubbing of grain during handling, for these beetles to survive. Any home can be invaded by these beetles through the transportation and storage of grains or grain products such as cereals, macaroni, flour, etc.
Flour beetles are not known to carry or spread any diseases that affect humans. Nor do they attack anything other than grain or starch foods (at least not for long). However, in search of their favorite foods, they may become an annoyance, invading all areas of a home.
The beetles (adults) are shiny, flattened, reddish brown insects about 1/7″ long, and very active. The larvae are brownish to yellowish white, worm-like insects with three pairs of legs. They are about 1/16″ when fully grown.
Both beetles can live up to three years. Unlikely to survive Maine’s winter temperatures, they seek protection in heated areas or areas where high moisture grain is heating. Generally, these insects are considered weak fliers, but warm temperatures make them more active and, with the help of a wind, they can apparently move long distances.
Sanitation – Emptying and cleaning food containers before replenishing supplies and checking foods stored for long periods are the most effective means of keeping flour beetles out of your kitchen. Plastic, glass, or metal containers with tight fitting lids are also helpful.
Never discard foods infested with flour beetles. You may give it the 125-140°F heat treatment in an oven for 30 to 45 minutes to kill all stages of development. Placing the infested food in a freezer for five days at 0°F should also kill the pests. Otherwise, the infestation may spread. A vacuum cleaner is an excellent aid, but the bag should be sealed before disposing.
Insecticides – Household sprays such as cyfluthrin, permethrin, resmethrin, or tetramethrin must also be used according to directions but only in cracks, crevices, corners, and under or behind things where insects are likely to hide.
When Using Pesticides
ALWAYS FOLLOW LABEL DIRECTIONS!
Pest Management Office
491 College Avenue, Orono, ME 04473-1295
1-800-287-0279 (in Maine)
Information in this publication is provided purely for educational purposes. No responsibility is assumed for any problems associated with the use of products or services mentioned. No endorsement of products or companies is intended, nor is criticism of unnamed products or companies implied.
Published and distributed in furtherance of Acts of Congress of May 8 and June 30, 1914, by the University of Maine Cooperative Extension, the Land Grant University of the state of Maine and the U.S. Department of Agriculture cooperating. Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment.
Call 800-287-0274 or TDD 800-287-8957 (in Maine), or 207-581-3188, for information on publications and program offerings from University of Maine Cooperative Extension, or visit extension.umaine.edu.