Image is not to scale.

General Characteristics:

- Both species range in length from 2.5-3.7mm, are flattened and reddish-brown in colour and possess six sawtooth-like projections on each side of the thorax

- Both are common stored-food product pests that infest cereals, cornmeal, cornstarch, popcorn, rice, dried fruits, breakfast foods, flour, rolled oats, bran, macaroni, sugar, drugs, spices, herbs, candy, dried meats, chocolate, bread, nuts, crackers, raisins, dried dog and cat food, among other foods

- They possess running legs

- They can enter tightly sealed packages and can infest quickly

- They do not sting or bite humans or animals

- Geographic range is worldwide

- It is difficult to distinguish between these two species without magnification:
(distinguishing characteristics below)

Sawtoothed Grain Beetle (Oryzaephilus surinamensis)
- Under magnification, projections behind the eyes are curved and wide in appearance
- Suited to both cool and warm climates
- Does NOT fly

Merchant Grain Beetle (Oryzaephilus mercator)
- Under magnification, projections behind the eyes are pointed and narrow in appearance
- Primarily found in warmer climates
- This species is capable of flight

Reproduction:

Sawtoothed Grain Beetle (Oryzaephilus surinamensis)
- Female lays about 400 eggs loosely in milled products or inside a crevice in a whole kernel
- Eggs hatch in 3 to 5 days and begin actively feeding
- Full grown larvae are 3-4 mm long
- Pupation occurs in cocoons for about one week and adult matures in 3-4 weeks
- For all life cycles to complete temperature must range between 17-37 °C

Merchant Grain Beetle (Oryzaephilus mercator)
- Female lays about 200-285 eggs over a 3-month period
- Eggs hatch when temperatures reach 20°C to 37.5°C
- Larvae development ranges from 15 to 46 days, depending on food and humidity (70% humidity is optimal)
- Pupae emerge as adults in about 10 days

Signs of Infestation:

Sawtoothed Grain Beetle (Oryzaephilus surinamensis)
- Feed on dry grain, destroying the germ in the kernels
- May infest such foods as nuts, sugar, dried fruits and meats, and many other products
- Unopened damaged packaging can be an indicator of his species

Merchant Grain Beetle (Oryzaephilus mercator)
- Normally species’ eggs are carried into the home in food
- After hatching, the larvae (and later the adults) feed on this food and then spread to adjacent foods
- In apartment buildings, they sometimes migrate, spreading from unit to unit
- Unopened damaged packaging can be an indicator of his species

Control Techniques:

Sawtoothed Grain Beetle (Oryzaephilus surinamensis)
- Prevention through sanitation of food holding containers is necessary for control
- In winter, it can also be controlled by cooling the grain to -5°C and holding it at that temperature for 12 weeks
- Infested product should be place in a freezer for 12 weeks or disposed of accordingly
- Insecticides may be used for existing infestations ACCORDING TO LABEL SPECIFICATIONS AND IN ACCORDANCE WITH FEDERAL, PROVINCIAL AND MUNICIPAL LAWS

Merchant Grain Beetle (Oryzaephilus mercator)
For infestations in homes:
- Heat infested food in the oven at 90°C for 1 to 2 hours to kill all stages of the insect and dispose of accordingly
- Remove uninfested foods and other items from shelves and drawers, then vacuum surfaces, crevices, grooves, slider rails, breadboards and floor around baseboards, behind stoves and refrigerators, and other places where crumbs accumulate
- Wash all affected areas with a strong detergent
- Insecticides may be used for existing infestations ACCORDING TO LABEL SPECIFICATIONS AND IN ACCORDANCE WITH FEDERAL, PROVINCIAL AND MUNICIPAL LAWS

For infestations in granaries:
- Prevention is the best approach to control of the pest
- Clean grain bins thoroughly before and after each use
- Insecticides may be used for existing infestations ACCORDING TO LABEL SPECIFICATIONS AND IN ACCORDANCE WITH FEDERAL, PROVINCIAL AND MUNICIPAL LAWS

Please click here to contact a Focus Pest Control professional to inquire about further treatments for this pest species.


References:

Benett, Gary W., et.al.. Truman’s Scientific Guide to Pest Control Operations. Duluth: Advanstar Communications, 1988. p. 216.

“Merchant grain beetle - Oryzaephilus mercator ” (On-line).Canadian Grain Commission. Accessed Jan. 11, 2010 at http://grainscanada.gc.ca/storage-entrepose/pip-irp/mgb-cg-eng.htm.

“Ohio State University Extension Fact Sheet (Entomology) - Sawtoothed and Merchant Grain Beetles” (On-line). Ohio State University Entomology. Accessed Jan. 11, 2010 at http://ohioline.osu.edu/hyg-fact/2000/2086.html.

“Saw-toothed grain beetle - Oryzaephilus surinamensis ( L.)” (On-line).Canadian Grain Commission. Accessed Jan. 11, 2010 at http://grainscanada.gc.ca/storage-entrepose/pip-irp/sgb-cdg-eng.htm.

Disclaimer:

The Focus Pest Control ‘Pest Library’ is an educational resource written largely to educate the general public about common pests in Ontario. The Focus ‘Pest Library’ does not include all species in Ontario, nor does it include the most recent scientific data about species we describe. Though we edit our accounts for accuracy, we cannot guarantee all information in those accounts. While Focus Pest Control staff and contributors provide references to books and websites that we believe are reputable, we cannot necessarily endorse the contents of references beyond our control.

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