A small gray or brownish moth that appears in your kitchen pantry or cabinet might seem easy enough to dismiss, but it is nothing to take lightly. This little moth is probably the adult phase of the Plodia interpunctella insect species, and where adult moths are present, your pantry or cupboard is probabably also harboring eggs, pupae (caterpillars), and pupal shells. With a single female moth capable of laying 100 to 300 eggs, each of which can proceed through the entire lifecycle in about 50 days, you may already be facing a major infestation.
Biology of the Pantry Moth
P. inerpentella is one of several insects known to feed on stored grains and other dry foods. It is known by several common names, including pantry moth, Indianmeal moth, flour moth, grain moth, and weevil moth. The adult moth is quite small, 1/4 to 3/8 inch in length, with a wingspan of 1/2 to 3/4 inch, making it easy to overlook until your kitchen storage space is overwhelmed by the insects.
The insect is found almost everywhere in the U.S. These pests will feed on almost any dry foods, especially raw and processed grain products, cereals, pastas, and dog and cat food. An infestation is not a sign of your own poor housekeeping, because in most cases the initial infestation occurs at a commercial food processing or packaging facility and comes into your home from packaged foods.
The 100 to 300 tiny white eggs laid by adult female moths will hatch in a few days into small white caterpillar larvae, less than 1/2 inch long, which spend the next several weeks spinning webs and eating your stored foods before forming pupae that will hatch into more moths. The entire process can take from 1 to 10 months, so by the time you find visible moths, there is a good chance you have a bad infestation in any dry food containers that are not sealed airtight.
It is often the webbing in the corners of pantries and cupboards that are the first indications of pantry moths—but at least this is better than pouring a cup of flour filled with squirming white worms.
3 Ways to Get Rid of Pantry Moths
Getting rid of an infestation of pantry moths is not hard, but it does involve quite a bit of work. Mostly it's a matter of closely inspecting each and every dry food item in your storage area, discarding affected items, and cleaning the area diligently before restocking. And because these pests are in food storage areas, pesticides are not an option when it comes to getting rid of pantry moths.
Remove, Inspect, Discard
Inspect all food in your pantry for signs of infestation. Look for larvae in and on food packaging. Also look for webs (as these may belong to moths, and not spiders). Grain-based products like flour, cereal, pasta, and baking mixes are moth favorites, along with nuts and sweets. But don't limit your search to these items. You may find larvae tucked into the edges of cans, on spice jars, or even in unopened packages and sealed canisters. If you have pets, be sure to check their food, too. Toss any infested foods that you find, and wipe down any affected cans with undiluted vinegar to kill the larvae. Infested items should go straight to your outdoor trash can. Placing them in your kitchen trash will only spread the problem.
With grain and nut products you plan to keep, place them in the freezer for a good length of time if you have the room. Wait until you're confident you've eliminated the problem before you move them back into the cupboard or pantry.
Give your pantry or cupboard a thorough cleaning. Pull out your shelf liners , and wash or replace them. Vacuum the shelves, paying special attention to the corners, undersides, shelf brackets, and mounting hardware. Vacuum the walls, baseboards, trim, floor, ceiling, and door (including the inside edge, hinges, and knob). Then, wipe down your pantry shelves with hot, soapy water or vinegar; and mop the floor. When you're done with your clean-up, remove the vacuum bag, and take it out to your outside trash bin (wash out the dust compartment, if you used a bagless vacuum). You don't want to harbor moth larvae in your vacuum.
Change Storage Methods
If you have space, store many grain or nut products permanently in the freezer or refrigerator rather than the pantry or cupboards. Also consider storing new groceries in a different spot (i.e., a good distance from the pantry). This can be a permanent strategy, or you may want to do it until you've had a chance to monitor the affected pantry and make sure the problem is fully eliminated.
In addition, consider transferring your grains and other dry food products in mason jars, tins, or other tight-sealing containers. This way, If you inadvertently bring food home from the grocery store that contains eggs, the moths won't be able to get out of the jar when they hatch, so you'll only have that one jar of food to throw away.
What Causes Pantry Moths?
Pantry moths almost always gain entry to your home through purchased dry food items that were contaminated at the food processing or packaging plant. Once in your home, they can spread if the products are stored in cardboard or thin plastic containers that allow the larvae to eat through and spread to other containers.
This insect feeds exclusively on dry food materials, especially grains, and it requires warm temperatures to breed and thrive. Even temporary storage of items in the freezer will kill any insects that are in the container. In regions where pantry moths are prevalent, this cold storage is a common strategy.
How to Prevent Pantry Moths
To avoid future infestations, consider storing your flour, baking mixes, oatmeal, and nuts in the freezer, or freeze these items for a week before moving them to your pantry. It will kill any larvae that might be present in the foods that you bring home from the store, so you don't introduce them to your pantry.
Bay leaves, lavender, cedar, and mint are known to repel moths. Fill sachets with one of these, and tuck them inside your pantry as a deterrent. Replace them from time to time, so they remain effective.
Clean up food messes in your pantry as soon as they happen, and give your pantry a thorough scrub several times a year. It will help you to avoid infestations and alert you to any potential problems before things get out of hand.
If you maintain a grocery stockpile, be sure to inspect it regularly for moth activity, and to follow the same food storage practices that you follow in your kitchen. You probably don't visit your stockpile near as often as you visit your pantry, so it would be easy for a problem to go unnoticed.
Pantry Moths vs. Clothes Moths
Pantry moths are a different species from the common moths that cause damage to fabrics in closets and dressers. The two most common fabric-eating moths are Tinea pellionella and Tineola biselliell. They look quite similar to pantry moths, with the same shape and size, but these insects are not known to infest food-storage areas. Pantry moths usually have more distinct reddish-brown hues on the outside wings, while clothes moths are more uniformly gray.
However, in a home with a severe infestation of pantry moths, the insects sometimes use nearby fabrics as a site for laying eggs. It's possible you may find signs of pantry moth webbing and even tiny caterpillar larvae in clothing storage areas located near pantries and other food storage areas. Pantry moths, however, do not consume textile fabrics. If you are also noticing holes in the clothing, then the infestation is likely clothes moths, not pantry moths.
Do Pantry Moths Spread Disease?
Although the presence of pantry moths (and especially their squirming larvae) may disgust you when you find them in your stored foods, there is no indiction that these insects spread diseases in the same way that common houseflies do.
Do Pantry Moths Bite?
Very few moths are known to bite people, and pantry moths are no exception. These insects simply feed on dry foods and are never known to bite.
Where Do Pantry Moths Come From?
In virtually every instance, pantry moths come into your home from purchased dry foods that were contaminated at food processing or packaging centers. Once in your home, however, they may spread throughout the house.
Will Pantry Moths Go Away on Their Own?
Pantry moths are not a seasonal visitor like cluster flies, box elder bugs, or some other insect pests. They will remain in your house—and spread—as long as there is dry food to eat or until you make efforts to eradicate them.