How To Prevent & Get Rid Of Grain Weevils

How To Prevent & Get Rid Of Grain Weevils

Emily Han
Mar 7, 2011
On Saturday morning we awoke to a rather horrifying sight: hundreds of little brown bugs pouring out of the pantry cupboard and across the kitchen floor. We've encountered ants, pantry moths, and grain beetles but this was a new one for us ... research revealed our new visitors to be grain weevils.

Here's what we've learned about grain weevils and how you can prevent them from invading your pantry…

Ground zero: a bag of wheatberries we purchased in the Midwest six months ago. You can see where the weevils chewed through the plastic.

Due to past insect problems, we're diligent about storing all foods in glass jars or plastic zip-top bags. Unfortunately, grain weevils (Sitophilus granarius, also called granary weevils or wheat weevils) can chew through paper and plastic packaging. That's how they got out of the bag of wheatberries you see above and into the rest of the kitchen.

But how did the weevils get there in the first place? You may want to skip this part if you're squeamish but we think it's actually quite fascinating ... A female weevil lays an egg inside a grain kernel. (She can do this up to 254 times!) The egg hatches and for one to five months depending on the season, the larva lives inside and feeds on the kernel as it grows. Upon reaching adulthood, the weevil emerges from the kernel to mate – and look for new grains to invade. We're kind of amazed to think of this process taking place inside a bag of wheatberries we purchased six months ago and forgot in the back of a cupboard!

That said, we definitely don't want it to happen again and these are the steps we're taking to eliminate and prevent grain weevils from our pantry:

• Inspect all grains upon purchase.
• Freeze grains for at least 1 week (or store permanently in the freezer) to kill any eggs.
• Buy grains in small quantities and eat within a reasonable period of time. (We certainly learned our lesson with this one!)
• Store grains in tightly sealed glass, metal, or sturdy plastic containers (not bags).
• Regularly clean pantry cracks, crevices, and shelves.
• Small bags of black pepper placed around the pantry may repel weevils.

• Discard any infested foods. Grain weevils can bore through plastic and cardboard so inspect everything thoroughly. (We chose to be safe and got rid of everything that wasn't already stored properly.)
• Vacuum pantry shelves, cracks, and crevices.
• Wipe shelves with white vinegar.
• Dispose of garbage and vacuum bags outside, away from the home.
• Check regularly for reappearance – it may take awhile to get rid of them completely.

Have you ever dealt with grain weevils? Any stories or tips to share?

More information: Granary and Rice Weevils (William F. Lyon, Ohio State University)

Related: Do You Have Grain Beetles Hiding in Your Pantry?

(Image: University of Missouri)

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