Dealing With Bugs in Flour


There is nothing worse than finding a bug infestation in your pantry. Find out how the bugs get into your flour and the best ways to prevent and eradicate them to protect your flour stash.

If you want to learn more about flour expiration, if it’s safe to eat expired flour, and the right flour environment, and proper disposal of old flour, head over to “Let’s Talk Flour Storage!”

Dealing with bugs in flour

I am about to tell you something really scary – there are already bugs in your flour. It’s a fact of life, bugs live with us, we don’t live in the hyper-clean environments that we think we do. I’m not going to get into the microorganisms that we can’t even see, but flour comes from wheat harvested out in good ‘ol Mother Nature. The same place of rain, sunshine, and… bugs.

This flour storage discussion involves the bugs already in your flour, and keeping the rest of the bugs out. No worries, I’m here to deliver peace of mind that you can overcome bugs in your flour.

According to Primal Survivor, “it can take weeks or even months for the eggs to hatch [in flour]. This means that sealed containers can’t stop a bug infestation because the bugs are already inside the containers.” Taking precautions, such as freezing, or microwaving the flour before storing will give you the confidence that weevils, eggs, and larva have been eradicated.

One word about bugs in your pantry. You may have been a person who always leaves the flour and other grains in the sacks they have come in. This method may have worked for years, and then one day… bam! You have a bug infestation. It could be weevils, moths, ants, or other bugs. The only way around it is to be vigilant and keep your pantry shelves clean!

Bags of flour leak out, spill, and spread dust on pantry shelves that attract bugs. Consider switching to airtight flour containers.

A reader mentioned that just the act of unrolling a flour bag emitted puffs of flour dust. If she managed not to spill anything, it was a good day. I’ve never thought of how much flour dust spreads when in use or leaks out of the bag.

I have an entire article covering airtight flour containers and finding the right size containers. Once you get the reality check on bugs, you might want to head over there!

Do I have bugs in my flour?

First off, don’t get paranoid about bugs in your flour. May I remind you that in some cultures, crickets are a prized protein! You’re probably thinking, “how can manufacturers sell food with bugs in it?” The Food and Drug Administration sets the levels of natural or unavoidable defects in food sold to consumers.

inspecting food cabinet for bugs

inspecting food cabinet for bugs.

In Title 21, Code of Federal Regulations, Part 110.110, the Food and Drug Administration (FDA) establishes maximum levels of natural or unavoidable defects in foods for human use that present no health hazard. The “no inherent hazard to health” is specified for foods on this list, with wheat flour located at the bottom. Manufacturers are able to sell flour in stores because they meet the guidelines for minimal amounts of insect fragments in food. Not allowing these fragments would be like trying to stop air in food.

The good news is that proper storage of flour keeps everything under control. This organic matter won’t harm you (I bring back the cricket analogy). Also, sleep well knowing that anything you bake will kill eggs and weevils in the flour.

How can I tell if there are bugs, weevils, or other critters in my flour? Visually look at the flour, if necessary, stir it and spread it out to get a better look. If there is any movement, you have bugs. It may be as obvious, such as seeing flying moths or bugs darting around on shelves.

Other signs of bug infestations:

  • tiny holes at the top of the flour container or plastic bags
  • holes in cotton cloth (moths)
  • small cobwebs in the storage area (differs from spider cobwebs)
  • small piles of powder, similar to sawdust

Always discard flour if you find the flour has an active infestation of bugs. It isn’t worth the time trying to salvage the flour for use or taking the chance of infesting other food.

Sift your flour to see if any bugs are in it; discard flour if it contains weevils, beetles, insects, etc.

How to dispose of old or bug-infested flour

The best way to dispose of old flour is to put it back where it came from – out in nature. Dispose of old flour by sprinkling it in with green plant compost and mixing thoroughly. Regardless of disposal method, there are considerations to pay attention to:

  • do not dispose of old flour where pets or wild animals can eat it and get sick or where it would attract wild animals to a house
  • for bug infestations, minimize handling time inside the house to reduce spread of bugs
  • do not dispose of flour in an indoor trash can, bug infestations can spread to the house
  • dispose small amounts of old flour down a garbage disposal with adequate water so as not to clog drains

Preventing bugs in flour

Proper storage of flour will keep outside bugs out, but what about the eggs already in the flour? The absolute first thing to do is not store flour where it is too hot – this will hatch the eggs, and we don’t want that! 

Our friends in the the southern United States can tell tales of their battles of pantry moths in hotter climates. This can still be a problem in the midwest, especially if you don’t have air conditioning in your home. There are actionable steps you can take to keep bugs out of your flour, (heads up, one of them is storing flour in airtight food containers!).

USA Emergency Supply has a fascinating article about insect control in food. The author is an experienced long-term storage specialist in the state of Oregon. He realizes the importance of keeping emergency food supplies protected from insects. He mentions carbon dioxide as a successful fumigant, stating that it “worked great on every insect tested, in all their stages of development.”

Furthermore he states, “Effective bug control using oxygen absorbers requires all the air be removed. And then the authorities are careful to state that removing all the oxygen doesn’t necessarily kill bugs, but rather prevents them from thriving should they hatch.” Freezing and oxygen absorbers are a close second to carbon dioxide treatment methods.

I highly recommend that you read his article on Insect Control in Food to find out more about using carbon dioxide for treatment of insects in food. The common consumer will likely prefer the freezer method of killing bugs in flour.

Store flour in freezer to kill bugs.

Store flour in freezer to kill bugs.

Freezing dry goods to prevent bug infestations

This informative article by the University of Florida Extension recommends “Insects in infested foods may be killed by heat or cold if the item is of value. Infested foods may be placed in an oven at 130°F (54°C) for 30 minutes or a freezer at 0°F (-18°C) for four days to kill insects. If placed in a freezer, the commodity should be used as soon as possible since defrosting usually causes excess moisture in the item. The excess moisture could cause mold to form later. Freezing and defrosting the item in a tightly sealed plastic bag can limit condensation on the product.”

On the flour package I am holding in my hand now it states “store in clean, cool, and dry area away from strong odors. For longer shelf life, store in a refrigerator or freezer” and in another tip on the same bag, “store flour in an airtight container in a cool, dry place. For longer storage, place bag in a food-storage plastic bag, seal tightly and refrigerate or freeze. Bring flour to room temperature before using.” – Bakers Corner.

In his book “When Disaster Strikes,” Matthew Stein writes, “You can freeze containers of food to destroy living insects, but this will not usually kill their eggs. Refreeze the container after 30 days to destroy bugs that have hatched. Freeze in an upright or chest freezer for 72 hours at 0 degrees F or lower.”

In a similar note, the Entomological Society of America highlights the article in the Journal of Economic Entomology  called “Cold Tolerance of Bed Bugs and Practical Recommendations for Control” on success rates of killing bed bugs with freezing. The authors recommend that affected items be placed in plastic bags and that they remain in the freezer for 2-4 days, depending on the freezer’s temperature. I assume that if you can kill a stubborn bed bug, you can kill weevils and other flour pests by freezing.

It’s important to point out that there are numerous places on the Internet that warn not to freeze and refreeze flour and to bring it to room temperature before using. This preserves the quality of the flour to assure that it is in optimal condition for baking.

“[dry food] should be placed in plastic bags and… remain in the freezer for 2-4 days, depending on the freezer’s temperature [to kill bed bugs in all their forms]”

Some researchers say freezing will not kill all insects, but it is greatly effective. If you try the freezing method to prevent an infestation, it is a good idea to inspect your food for bugs on a regular basis. Early detection of a bug problem can prevent all your of food supply from sustaining insect damage.

Natural ways to deter bugs

Never underestimate a good cleaning of the pantry. Keep the shelves crumb-free with regular vacuuming and washing. Use vinegar, hot soapy water, or natural insecticide cleaners to discourage bugs. Don’t forget regular inspection to catch an outbreak as soon as possible!

You may have heard the wisdom (old wives’ tales) of placing laurel sprig, bay leaves, garlic, cloves, or even spearmint gum on shelves to deter insects. These natural remedies may help deter bugs and is certainly worth a try.

Cleaning a commercial kitchen in a restaurant.

Clean your pantry regularly, just as employees do in a commercial kitchen setting.

However, flour absorbs odors around it, especially strong ones. This includes chemicals, cleaners, new paint smells, garlic, onions, etc. Do you really want your flour smelling and tasting like garlic? A happy medium is not to put these natural defenses in the flour, but rather near enough to form a barrier to insects, yet far enough for the flour not to take on “interesting” odors. Storing items in the same closet may just be too close together.

Today’s modern solution to herbs are oxygen absorbers.Oxygen absorbers remove the oxygen from the container and will kill adult insects and prevent larval insects from surviving. Placing these inside sealed containers help to prevent oxidation and extend the shelf life of the flour as well. Be sure to visit the article ”   ” to learn about long-term food storage methods. Long-term food storage definitely is concerned about keeping food quality intact, and keeping bugs, mice, and other critters away.

Proper storage keeps outside bugs out

Three state extensions teamed together (one author being an entomologist) to write the article “Pantry pests: Insects found in stored food.” In the article they point out that “Pantry pests… can get into unopened paper, thin cardboard, and plastic, foil or cellophane-wrapped packages. They may chew their way into packages or crawl in through folds and seams.”

Authors: Jeffrey Hahn, former Extension entomologist; Laura Jesse, Iowa State University Extension and Outreach; and Phillip Pellitteri, University of Wisconsin-Extension.

To me, foil is shocking. Plastic lids are not even immune. When dealing with bugs, it’s smart to use several packaging barriers to protect flour. This website covers three proactive methods of storage that you can refer to:

  • Store flour in the freezer or refrigerator (the container type is not as important)
  • Store flour in special, airtight containers
  • Prepare flour using long-term storage methods

In conclusion…

Thanks for being brave and learning about bugs in your flour! Facing reality is the first step in getting rid of bugs. Now go get those airtight containers!

About the author 

Renee Matt

Renee is a former kitchen designer, home remodeling enthusiast (having lived through several DIY projects), and an Iowa farmwife. Renee is passionate about preparedness, garden skills, and knowing where her food comes from. Years of being a stay-at-home mom and supporting the family farm with hearty meals has been key to Renee's pantry readiness. She uses her professional IT background and expertise to bring the Everything Pantry website to life.

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