How to Get Rid of Weevils in Pantries and Cupboards

Your food-storage areas can be plagued by a strange-looking insect called a pantry weevil, but identifying and getting rid of weevils is easy. They feed primarily on grains but earned the name "flour bugs" because they are often found feeding in flour. You may also spot weevils in boxes or bags of stored whole-grain cereals, grains, nuts, and beans.

Food products containing raw wheat, oats, rye, barley, rice, and corn are most susceptible to weevils. Learning how to get rid of weevils may involve using several simultaneous but simple strategies.

What Are Weevils?

Pantry weevils are fairly small insects, so it is easy to overlook an infestation in your food storage areas. They are tiny, blackish-brown, and they are characterized by their noticeably long snouts not found in other types of insects. The three types of weevils that make up the group of common indoor kitchen pests range in size from 1/8 to 3/16 inches long.

Types of Weevils

Weevils comprise a very large group of more than 97,000 species of insects but there are only three common types of weevils found in pantries and cupboards. These three types of weevils are not the same types of weevils that can damage outdoor landscape plants and crops. You may find the following weevils in your pantry:

• Rice weevils (Sitophilus oryzae): Rice weevils are flying beetles, dull red-brown with four lighter spots. They are most common in slightly warmer climates.
• Granary or wheat weevils (Sitophilus granarius): Granary weevils cannot fly and are shiny red-brown; they are found in cooler climates.
• Maize weevils (Sitophilus zeamais): Maize weevils look very much like rice weevils; only a magnified examination of the reproductive parts will distinguish the two species.

What Causes Pantry Weevils?

Adult weevils look for shelter when it is hot and dry outdoors. They will come in through tiny cracks and crevices into your home or they gain entry into your house through purchased containers of whole-grain cereal products that were already infested during the food processing and packaging stage. Storage areas with a lot of spilled foods are more susceptible to weevil infestations, as well as those in which many partially used containers are stored.

Signs of Weevils

Pantry weevils lay eggs by boring a small hole in a grain of seed and laying a single egg that develops entirely inside the seed, emerging as an adult insect. Because so much of the lifecycle is spent inside the seed, and because the adult insects themselves are quite small, an infestation of weevils can go overlooked for quite a while until it becomes widespread. Look for these signs of a weevil infestation:

• Spotting many empty seed husks in the stored grain product.
• Seeing active adult beetles when you pour out a grain product for use in cooking.
  
• Finding dry, dusty residue from the hulls of seeds that have served as the home for eggs, larvae, and pupae.
• Finding dusty residue floating on the surface of water when pouring stored grain into a pot of water.

3 Ways to Get Rid of Weevils

Throw Away Affected Foods

Any open containers of cereal-grain products for which you suspect weevil infestation should be sealed and thrown away immediately. Also, throw away any nearby open containers. Even unopened cardboard containers may be suspect if they don't have sealed inner liners that are intact. When it comes to weevils, it's better to be aggressive about disposing of suspected foods.

Apply Heat or Cold to Stored Foods

If you find a food that is infested, or if you suspect it may be and you want to try to kill the weevils instead of discarding the food, you can usually kill the adult weevils, as well as the eggs, larvae, and pupae, by heating the product to 140 degrees Fahrenheit for at least 15 minutes or by freezing the product at 0 degrees Fahrenheit or lower for three days.

Clean to Eliminate Adult Insects

After emptying the cupboards and pantry, and after inspecting and discarding any suspect foods, thoroughly vacuum out the food-storage areas and clean them with hot soapy water or a disinfecting spray cleaner. Individual food cans and glass containers should also be cleaned before being returned to the cupboards. The goal here is to make sure that no adult weevils remain to establish a new infestation. These are very small insects, so they may escape your efforts unless you clean quite diligently.

Eliminate Eggs by Wiping Down Surfaces

In addition to adults, it's crucial that you do your best to eliminate any weevil eggs. One way to do this is to wipe down any potentially infected surfaces with vinegar or other products designed to kill bugs. If using a commercial product, follow the instructions on the bottle for the highest success rate.

Natural Pesticides

Utilizing natural pesticides like diatomaceous earth and boric acid can be effective in the battle against weevils. Some people swear by the practice of hanging bay leaves in pantries—or even placing a couple of bay leaves in packages of cereal grain products. Studies have shown bay leaf can be an effective means of repelling insects such as weevils or pantry moths.

Sticky Traps

Don't underestimate sticky traps when dealing with a weevil infestation. Strategically place sticky traps in areas you suspect are hosting weevils and in food storage areas. You can place the traps in corners and inconspicuous areas. Keep your kitchen cabinets, etc., dust-free, because dust can minimize the efficacy of sticky traps.

How to Prevent Weevils

Preventing weevil infestations requires routine inspection of any purchased foods coming into your house, along with periodic inspection of cereal-grain products being kept in your cupboards or pantries. It may be best to set a limit on how long you store partially used containers of grain products, throw old containers away, and buy new products regularly.

Some people like to routinely freeze containers of cereal-grain products for four days upon purchase, moving them into cupboard storage only after they have been disinfected in this way. Freezing will kill any weevils that are hitchhiking in commercial packaging. You can even store some of these products permanently in the freezer if you have the room. Grain products that are merely refrigerated will be less susceptible, though not immune to weevil problems.

Transferring grain products to sealed metal or glass containers can also prevent infestations. Before each use in cooking, carefully inspect the grain to ensure there's no insect activity.

Follow these additional tips to prevent weevils:

• Do not add new, fresh food to old food, and always clean out containers before refilling.
• Store pet foods, birdseed, etc. in buildings away from the house or basement areas well away from other foods.
• Do not purchase bagged or boxed foods with torn or damaged packaging.
• Do not buy bagged or boxed foods that are past their expiration dates.
• Do not overbuy food—just buy what you expect to use quickly. Or store excess in the refrigerator or freezer.
• Keep your pantry and other food areas organized, clean of loose foods, and free of crumbs. Clean up spills immediately.
• Keep food storage areas dry; weevils are also attracted to moisture.

When to Call a Professional to Treat a Weevil Infestation

If your weevil infestation is out of control and can't be eradicated, a pest control company may be able to help you. They can investigate for the source of the infestation which may have gone beyond the pantry or cabinets. Once the true source is discovered, the service can use extreme heat or cold, special sprays, or other types of applications to kill the bugs.