Bad Bugs: Saw-toothed Grain Beetle

By Alain VanRyckeghem, BCE
Technical Director

Saw-toothed Grain Beetle
Oryzaephilus surinamensis

This beetle causes many customer complaints in stored grains, dried fruit, cereal products, birdseed, and a wide variety of other foods. This little beetle is a fast moving insect. It can climb on any surface and hide in the tiniest cracks. It frequently follows floor crevices in its dispersal from an infestation source. It is unable to penetrate food packaging by chewing, but its small flattened size makes it an excellent invader of packages with gaps, and defects. This is a difficult insect to eradicate.

Life Cycle
Beetles lay 6-10 eggs per day, singly or in small clusters in crevices of grains and finely ground material. Eggs hatch in 3 days at 90°F (32°C) or 16 days at 64°F (15°C). There are usually three larval stages that develop to pupation in as few as 12 days and up to 32 days at the lower temperatures. Pupation can take as few as 4 days and as long as 16 days depending on temperature. Relative humidity extends the development time of this insect only slightly. Low relative humidity does not prevent development of this insect. Adults typically live for about 10 weeks, but can extend to 29 weeks under cooler temperatures. This insect could extend its lifespan over the winter season and be an active pest in early spring. This Sawtoothed grain beetle can survive large extremes in temperature and humidity compared to the Merchant grain beetle.

Biology & Behavior
The Saw-toothed grain beetle is a common pest of processed foods in warehouse storage, retail stores, and pantries of homes. It prefers to feed on foods made from rice, corn, wheat, and other cereal grains. They do not usually attack nuts, seeds, beans, pet foods with high oil content or whole unbroken grains, but may feed on residues.

The female deposits most of its eggs in the first 2-3 weeks and will decline rapidly by the 10th week. The adult beetle is small and fl at, about 1/10 of an inch (2.5mm) and has characteristic teeth on the sides of the thorax. It can be distinguished from the Merchant grain beetle (O. mercator) by its slightly smaller eyes and larger “temple” region behind the eye.

The adults and larvae are tolerant to cold 33°F (0°C) for a few weeks, but will die within 24 hours at 0°F (-18°C). The upper range for survival in heat is about 102°F. Exposing beetles to 12 hours at 114°F (46°C) will kill all stages.

Most of the residual insecticides approved for use in food storage areas are very effective for control. Careful application in cracks and crevices and some spot application would yield the best results.

There are no commercially available pheromones for this insect, but it is attracted to unique food odors from grains and plants. The PC Floor Trap and lure was designed to specifically trap the grain beetles and allow them to remain alive, thus providing a natural pheromone source for more beetles to become entrapped. Floor level traps should be placed on cracks and crevices and along walls or posts near food storage.

Check them weekly and clean out the traps by shaking them out over a container of soapy water. Do not clean out the trap with soap and water as this removes the natural pheromone and Teflon coating that prevents escape. Food lures should be replaced monthly.


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