Red Flour Beetle

species: tribolium castaneum
common names: red flour beetle
hosts: flour
notes:

Agriculture and Agri-Food Canada Insect Identification Sheet No 75. March 1981

Red Flour Beetle

Tribolium castaneum (Herbst)

Although it is found most often in warmer climates, the red flour beetle also occurs in the temperate regions where it survives the winter in protected places. It is found across Canada, mainly in bins where grain is stored for long periods, such as farm silos and country elevators. It can also be a pest of stored products such as peas, beans, nuts, dried fruits, drugs, spices and chocolate, and of herbarium and museum specimens.

Injury:

The red flour beetle feeds on a wide range of foods, but is most important as a pest of stored grains, oilseeds and their products. It prefers damaged grain, but will attack whole wheat, feeding first on the germ and then on the endosperm.

Life History:

The adult is a small reddish brown beetle about 4 mm long. It closely resembles the confused flour beetle. Each female lays 300 to 400 eggs and egg-laying occurs when the temperature is over 20 degrees. Hatching produces wormlike larvae that are whitish and marked with pale brown bands. When fully grown, they are about 8 mm long. Development of the pest from egg to adult takes 15 to 20 days under optimum conditions — a temperature of 35 degrees and relative humidity ranging between 70 and 90%. It can also develop under dry conditions; for example, a relative humidity of 10% or less. The red flour beetle will fly when the temperature is 25 degrees or higher, so infestations can spread quickly. Temperature limits for complete development are 20 to 40 degrees.

Control:

Because these insects live outside the kernels, they are vulnerable to mechanical handling of grain. Consequently, their numbers are reduced when grain in an infested bin is turned and when it is loaded into a boxcar. For this reason, the insects are seldom found in terminal and other elevators with a high through-put and are more likely to show up in grain that has been stored for some time. To help prevent an infestation from developing, empty bins should be cleaned. In winter, cooling the grain to - 7 degrees and holding it at that temperature for 6 weeks has proven effective. Consult your provincial agricultural representative for full details on controlling the pest.