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How do I get Rid of Grain Weevils?

H. Lo
H. Lo

Grain weevils are pests that feed on and destroy stored seeds and whole grains. The simplest way to get rid of these pests is to locate and throw away any of the infested grain that they are feeding on, and then to carefully clean the storage area afterward. It is also possible to kill grain weevils, which are sometimes also called snout beetles, by exposing them to extreme heat or cold. In addition, insecticides do have an effect on getting rid of these pests.

Until there is a presence of adult weevils, it is not always apparent that grain is infested. This is because female weevils lay their eggs in grains; in doing so, they drill holes and then cover them up again. Adults emerge from these grains, but larvae are hidden inside until they become adults, at which point they drill holes to get out. To see if grain is infested, look for these exit holes. After disposing of infested grain, cleaning the area in which it was stored will get rid of any lingering weevils.

Heating infested grain in the microwave can kill eggs and larvae.
Heating infested grain in the microwave can kill eggs and larvae.

Discarding grain might not be a practical choice for some people. To kill eggs and larvae, infested grain can be heated in the oven or microwave, as well as frozen. This process does have a drawback, though, as extreme temperatures reduce grain germination. Decreased germination can be unacceptable for those who anticipate using the seeds for planting.

Barley, a type of grain.
Barley, a type of grain.

Insecticides are generally dangerous and do work, but only to a certain degree. They have to come into direct contact with the weevils in order to be effective. If desired, insecticide can also be used as a prevention measure. A spray of an insecticide that contains pyrethrins provides a protective layer over the seeds or grain, inhibiting female grain weevils from depositing their eggs. Large infestations that cannot be eliminated might require a call to a professional for fumigation.

Grain infestations can be caused by any of three types of grain weevils: rice, granary and maize. Rice weevils and maize weevils are similar in appearance; they are dull red to black with four red to yellow markings on the back, though maize weevils are the bigger of the two. Both these species can fly, which is not the case with granary weevils. Granary weevils are red to black in coloring and larger than both rice and maize weevils. Grain weevils are a nuisance all over the world.

Discussion Comments


We had hundreds, if not thousands of those tiny black Weevils (long nosed grain weevils) in our basement. We don't keep any food in the basement. We were told by experts and exterminators, they were just coming inside to get out of the cold. However, had a nagging feeling that there must be a food source somewhere, but could find no food source for those little black bugs.

My family dealt with those bugs (and pesticides) for four months, then finally, I found their food source (after searching for months). We bought a Bean-bag toss, and the bean bags were stored in the basement (and filled with indian hard corn). I got rid of them and finally, no more bugs. Who would have guessed it was the bean bags? I cut a bean bag open and found hundreds. Just remember, if you are super infested, they must have a food source.


@LisaLou - I started doing the same thing after a bad grain weevil infestation. I figured the only way to prevent it was to keep my flour in the freezer. It didn't seem to matter how air tight I thought the container was, they always seemed to find a way to get in.

It can be frustrating because if you don't have much room, the bags of flour can take up quite a bit of space in your freezer. Fortunately I have a big freezer in my basement so I have the extra space to store my grain.

If you don't have much space I would buy as small a bag as you can. It is not as convenient, but better than wasting you money when you have to throw it away.


I hate grain weevils. There is nothing so frustrating as getting ready to make a batch of cookies or brownies and discover that the grain bugs are in your flour. I don't take any chances and just end up throwing everything away.

After doing that several times, I don't keep much flour or grain in my cupboards anymore. I somehow find room either in the refrigerator or freezer so that I don't have to worry about it. Seems like the longer you go without using it in your cupboard, the more chances you have of finding them.

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    • Heating infested grain in the microwave can kill eggs and larvae.
      Heating infested grain in the microwave can kill eggs and larvae.
    • Barley, a type of grain.
      By: 1999istek
      Barley, a type of grain.