How to Identify the Lesser Grain Borer and the Sawtoothed Grain Beetle

The term “weevil” is often used broadly to describe any stored grain insect, but profit-robbing grain bugs come in many different species. Weevils present their own unique host of problems, (see our blog on weevils here) but if you’re having issues with another species, you should correctly identify the culprit and plan to treat accordingly.

Let’s take a look at the specific traits, habits, and signs of infestation that will help you identify a couple of common stored grain pests, the lesser grain borer and the sawtoothed grain beetle.

Identifying the Lesser Grain Borer

Also known by their Latin name, Rhyzopertha dominica, lesser grain borers are voracious feeders. At approximately 1/8” long, with brown or black cylindrical bodies, lesser grain borers can be difficult to spot, as their heads are not usually visible from above. They are strong fliers, capable of rapidly spreading infestations. Upon close inspection, lesser grain borer larvae can be spotted and identified by their c-shaped white bodies with small dark heads and three pairs of small legs.

The life cycle of lesser grain borers is variable based on temperature, but they tend to live a minimum of 25 days. In terms of feeding habits, both adults and larvae bore into grain kernels, hence their name, feeding on whole grain or dust.

Seeing live adult insects in grain is a surefire sign of infestation, along with any fragmented kernels, powdery residue, or a sweet musty odor. Damaged grain will have a “shot hole” appearance.

Our recommendation for control:

• Clean and spray grain bins with Gravista^_® Insecticide prior to grain storage.
• For treatments of six months or longer, inspect and treat incoming grain with Gravista® Insecticide and monitor grain throughout your storage period.
• To bring a boost to short-term grain storage of six months or less, and for rescue treatments, treat with Centynal™ Synergized Insecticide.

Identifying the Sawtoothed Grain Beetle

Sawtoothed grain beetles, or Oryzaephilus surinamensis, often leave their mark by overheating grain or by a visible population build-up. If you come across them, you can recognize them by their brown flattened body at approximately 1/10” - 1/8” long. It gets its name from the distinctive saw-tooth projections on the sides of its thorax. Sawtoothed grain beetles are flightless, and they have running legs that look much like those of cockroaches.

Sawtoothed grain beetles live a minimum of 28 days, during which they often infest oats, wheat, barley, and animal feed, to name just a few. Both adults and larvae feed on grain dust, although the larvae prefer germ.

Our recommendation for control:

• Clean and spray grain bins with Gravista^_® Insecticide prior to grain storage.
• For treatments of six months or longer, inspect and treat incoming grain with Gravista® Insecticide and monitor grain throughout your storage period.
• To bring a boost to short-term grain storage of six months or less, and for rescue treatments, treat with Centynal™ Synergized Insecticide.

Identifying the exact kind of stored grain insect that may be causing problems in your stored grain is crucial to successful control. Be on the lookout for more information on correct identification on our social channels. In the meantime, visit bugfreegrains.com.