Also known as: Oryzaephilus mercator
Description & Identification
The merchant grain beetle (Oryzaephilus mercator) is a common grain beetle found worldwide, including throughout Canada. This pest is notorious for infesting a variety of stored products, making it one of the most frustrating flour beetles homeowners encounter in their kitchens and pantries.
Merchant grain beetles are frequently found in:
- Packaged grains and cereals
- Dried fruits and nuts
- Flour and baking mixes
- Candy and chocolate
- Pet food
- Tobacco products
Physical Characteristics
- Size: About 2.5–3 mm in length
- Colour: Brown to reddish-brown
- Shape: Slender, flat body that allows them to crawl into tiny cracks and food packaging
- Adults: Often mistaken for sawtoothed grain beetles but can be distinguished by the width of the temple (merchant grain beetles have narrower temples)
- Larvae: White to pale yellow, flattened, and typically found inside food products
Like other grain beetles, merchant grain beetles can squeeze into improperly sealed packages, contaminating food quickly.
Signs of a Merchant Grain Beetle Infestation
A merchant grain beetle infestation can often be identified by:
- Adult beetles crawling near pantry shelves or food storage areas
- Damaged food packaging with tiny holes or tears
- Clumped or discoloured food caused by larvae feeding
- Unpleasant, stale odours coming from infested products
If you notice these signs, you’ll want to act quickly before the infestation spreads.
How to Get Rid of Merchant Grain Beetles
If you’re dealing with merchant grain beetles, here are effective steps to eliminate them:
- Inspect all food – Check every dry good, including flour, cereals, and baking supplies. Discard anything showing signs of contamination.
- Heat treatment – Place infested products in the oven at 58°C (136°F) for one hour to kill beetles and larvae.
- Freezing treatment – Freeze items at -18°C (0°F) for at least six days.
- Clean thoroughly – Vacuum pantry shelves, cracks, and corners. Dispose of the vacuum bag immediately outdoors.
- Call professionals – For large or recurring infestations, pest control specialists can provide safe, long-term treatment.
How to Prevent Merchant Grain Beetles
Preventing a grain beetle infestation is much easier than getting rid of one. Here are proactive steps:
- Inspect food before buying – Check packaging for holes or damage in-store.
- Report infested goods – Notify the store if you find contaminated products.
- Use airtight containers – Store flour, cereal, rice, and baking goods in sealed glass, metal, or heavy-duty plastic containers.
- Rotate pantry items – Use older products first to avoid long-term storage.
- Maintain cleanliness – Wipe down shelves and storage bins regularly to remove crumbs and food residue.
By understanding how to identify, remove, and prevent merchant grain beetles (and other pantry pests like flour beetles), you can protect your food supply and keep your kitchen pest-free.