by David Moore
Manager of Technical Services and Board Certified Entomologist
with contributions by Eric Smith, PhD, BCE
These are those small beetles, moths, and worm-like critters that are commonly found in stored food items such as flour, pasta, cookies, cereals, candy, nuts, spices, rice, beans, dried pet food, dried fruit, etc. The worm-like critters are the larvae (immature stages) of the beetles and moths. Several of these pests are pictured in the Dodson Pest ID Guide elsewhere on this web site.
These pests are usually brought into the home in food items purchased at the grocery store. However, many of them live successfully in the out-of-doors, especially in agricultural areas, and some are associated with bird nests or dead insects, and others with moldy situations.
In the United States, the Indianmeal moth (scientific name is Plodia interpunctella) is by far the most commonly encountered of the stored product pests found in homes, grocery stores, anywhere dried pet foods are produced or stored, including bird seed. Given warm conditions, it takes only a total of about 25 days for the eggs to hatch, the larvae to become full grown and pupate, and for the adults to emerge. The mature larvae leave the food source and wander about to find a suitable pupation site, and in the process often cause concern because they are mistaken for clothes moth larvae.
The beetle of major concern is the warehouse beetle (scientific name is Trogoderma variabile). The problem here is that the larvae are covered with hundreds of sharp hairs. If larvae and/or larval molt skins are not detected in cereal or other food that is eaten, severe gastrointestinal problems can result, especially in infants. Warehouse beetles are common outdoors and readily feed on dead insects such as those found on windowsills and along baseboards, and from here adults move to lay their eggs in available stored food items.
So, what can be done to help prevent an infestation? This consists of doing the following:
- Carefully inspecting all food items for human, pet, and/or bird consumption being brought into the home for stored product pests.
- Do this first when selecting the item in the grocery or supply store, and then again as soon as they are brought into the house before storing them away.
- At home, you can empty the contents of any suspect package/box in one thin layer at a time onto a white enameled pan to look for pests.
- Put each food package into its own tight sealing plastic bag or container, or empty the contents into a screw-top container or Ziploc-type bag.
- For additional prevention, store these containers in the refrigerator; the cold will greatly retard/stop the development of these pests.
- Housekeeping or sanitation.
- Practice proper item/product rotation or FIFO (first in, first out/used).
- Immediately remove all spilled food product, especially in cracks and crevices. A vacuum with crack and crevice tip works well.
- Throw out any item that is more than one month beyond its expiration date, unless it has been stored in the freezer or refrigerator.
What can/should you do if you find infested food materials?
You have 3 options:
- You can obviously throw the whole bag or box away, and be sure to do this if the product is heavily infested. Seal it in a plastic bag and put the bag in an outside trash can.
- For lightly infested food material, put the bag into a freezer (not the self-defrosting kind) for 4 days at 0°F to kill the pests. If the product is bird seed or dried pet food, then remove the seed/pellets as needed and feed it to the animals. They will not mind the extra protein and crunch.
- For lightly infested food material, but not recommended for high-fat items such as dried pet foods/treats, spread the food (not more than 1/2″ deep) on a shallow metal/glass pan and put it in a 125° F oven and heat it for 30 minutes. Once it has cooled, bag it in a Ziploc-type plastic bag and store it in the refrigerator until needed.
If the infested food is flour or other ground material, be sure to sift it before use. Visually inspect other items such as crackers before storage or use and discard any pests found.
What should you do if you find small beetles or moths in places other than the pantry?
- Many of the stored product pests will feed on a wide variety of organic materials. Such items include ornamental items (Indian corn stored away for the season), jewelry or decorations made of seeds, dead insects in light fixtures or windows, nuts in a bowl in the family room, etc.
- If you find small insects, adults or larvae, other than in the pantry, correct identification is critical to tell one what may be infested, e.g., clothes moths in stored woolens, carpet beetles infesting a prize rug or wall hanging, foreign grain beetles coming to lights at night, drain/moth flies breeding in a drain, etc.
- So, it’s time to call for an inspection by a pest management professional to help solve your problem and give you peace of mind.