How to deal with common grain pantry pests

Grain-loving pantry pests contaminate food, but do not cause foodborne illness.

A flour beetle.
Photo: MSU Plant Pest and Diagnostics.

Two of the most common pantry pests to invade a food pantry are the red flour beetle and the Indian meal moth. Invasion can occur at any time during the travel from farm to table. Favorite foods of these pests are grain products. The pests often invade open packages.

These invaders ruin grain products in the pantry. Once people discover them, they do not want to eat the food.  However, these dreaded pests do not cause foodborne illness.

Pantry pests may be discovered in grain products such as cake mixes, flour, biscuit mix, crackers, cornmeal, dried beans, dried fruit, dry pet food, nuts, powdered milk, seeds and birdseed.

The red flour beetle is reddish-brown. It measures about one-eighth of an inch in length. The larva is white and about ¼-inch in size. Adult beetles do not mind being out and about on countertops or pantry shelves. The larva and beetle prefer to munch away on particles of crackers, cookies, crumbs, or the delicate heart of a grain kernel. As they eat away, red flour beetles create a foul odor and cause an unpleasant taste to the grain product.

Indian meal moths have reddish-brown wings that shimmer in the light.  The wingspan is roughly ½ inch to 5/8 -inch wide. With cream coloring, the larva can have pink or green discolorations. The larva causes the most destruction by spinning a web around the food they consume as they develop into moths.  This webbing makes the food products unappetizing and contaminated.

Often the pests appear in open packages, but they can chew their way through thin cardboard, paper, foil, or cellophane.

For the best solution to the pantry pest invasion, Michigan State University Extension suggests throwing away the soiled food. Empty the pantry shelves of all food products.

Check all open flour, noodles, cake mixes and dry pet food. Discard any packages that contain evidence of the bugs.  If you are not sure about unopened boxes, put them in the freezer at 0 degrees Fahrenheit for four days to kill the eggs or bugs.

Next, vacuum all cracks and crevices of the cupboards and pantry shelves. Empty the vacuum bag or container in the trash. Remove the garbage from the area so the bugs cannot come back in.   

Wash the shelves with soapy water and rinse with clear water. Allow the cupboards to air-dry. Using strong bleach or ammonia will not deter the bugs from coming back. It is unwise to use household pesticides in the food storage area because chemical contamination may occur.

Decorations or arrangements made of plant products and seeds should be put in the freezer for four days to kill the bugs.

Prevention is the best policy.  Here are some tips to prevent pest invasion in food pantries.

  • Buy grain products in small quantities.
  • Purchase cereals, flours and pasta from a source that has a regular turnover of grain products.
  • Inspect the packages for evidence of contamination before purchasing. Make sure there are no pinholes in the cellophane or cardboard seams.
  • Store cereals, grains, and flours in airtight containers like glass, metal, plastic with tight lids.
  • Put new packages in the refrigerator or freezer before putting them on the shelf to help prevent the hatching of eggs.
  • Clean up any spilled food or crumbs.
  • Keep the pantry clean.

Prevention is always the best policy. Don’t let pantry pests bug you; take action. For more information about pantry pests and food safety, contact the Michigan State University Extension Food Safety Hotline at 877-643-9882.

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