Saw Tooth Grain Beetle

General Facts

The Sawtooth Grain Beetle is a major pest of stored food products. It doesn’t fly and can be easily mistaken for Red Flour Beetles or Confused Flour Beetles. This beetle’s small size allows it to enter tiny cracks and infest broken grain kernels but normally won’t infest whole grain. It has a keen sense of smell and strong chewing mouth parts that allow them to access food which is stored inside boxes and plastic bags. They will feed upon pet food, cereal, pasta, spices, rodenticide, dried fruit and vegetables, eggs of other insects, nuts, grass seed, nuts, spices, drugs, chocolate, and tobacco.

The Sawtooth Beetle is dark brown and about 1/8th inch long, with a flat body and six tiny projections on each side, just behind the head (on its thorax) that resemble the teeth of a saw. The female beetle deposits eggs in and around grain products (like flour). It lays its eggs on foodstuffs at an average rate of about 8 per day, with totals over 350 per female in a lifetime. The eggs are deposited with glue like excretions, which helps to attach them to surfaces where food is likely to be available. The eggs will hatch in about 8 to 14 days and the larvae begin feeding immediately. They are usually found in top inch of the food source. This Beetle lives a long time of up to 3 years and its fast developing. The total life cycle is 20 – 80 days at 18 – 37°C (64 – 99°F). Larva will go through 2-4 molts which will occur over 3-5 weeks. Pupa will emerge as adults in another couple of weeks and their cycle is complete.



Although broken kernels are the preferred food of both species, sound kernels will sometimes be penetrated and fed on. The dry weight of grain may be reduced, but total weight may increase because of water absorption caused by the metabolic processes of insect populations. Molds may begin to grow on the gain, further reducing grain quality and value. The presence of live insects and/or insect parts can also result in reduction of grain value. In some cases, grain can be rejected at the terminal.



Prevention is the best strategy to avoid insect problems in stored grains. Proper bin sanitation before introduction of new grain minimizes the need for pesticides. Good sanitation involves the removal of old grain and dust in and around the gain bin. This includes removal of old grain from corners, floors, and walls. Any grain remaining when a bin is emptied can harbor insect infestations which will move into the new grain. Grain that is to be stored for longer than six months may need a protective application of an approved insecticide.

Grain placed in a clean bin should be checked at two week intervals during warm months and at one month intervals during cooler months for the presence of hotspots, moldy areas, and live insects. If any of these conditions exist, the grain should be aerated to lower the moisture level and temperature.

Fumigation should only be used as a last resort. Because of the high toxicity of registered fumigants and technical knowledge needed for their proper use, a qualified pesticide applicator should be contacted if fumigation is required.