Barbara J. Bromley, Mercer Co. Horticulturist 04

At one time or another nearly everyone will find food-infesting insects in a room in the house (usually the kitchen) or in a food product. The most commonly encountered pest of stored products is the Indianmeal moth, (Plodia interpunctella).

Damage: The moths themselves do no damage to food products. Their primary responsibility is to mate so the female can lay eggs. The eggs hatch into caterpillars that can chew through packaging and feed on the available stored product. Indications of infestation include small webbed particles attached to the sides of packaging. Severe infestations are manifested by the presence of large numbers of caterpillars and frass (insect droppings and food particles) at the bottom of packages. If these pests are inadvertently eaten cooked or raw, they will cause no ill effects. (Although it may be disgusting to contemplate, they could be considered an additional source of protein in the diet. Yuk.)

Description: The moth has pale gray wings. The outer forewing is reddish brown with a coppery luster. At rest, the moth appears to have a pale band from its head through the first 1/3 of its wings. These moths are attracted to light, unlike the physically similar clothes moths. The caterpillar is generally a dirty white with a dark head, but its color can be influenced by the foods eaten.

Foods: Favorite foods of the Indianmeal moth larvae include dried fruit, seeds, crackers, nuts (shelled and unshelled), powdered milk, spices, candies, bird seed, dried pet food and biscuits, oatmeal, prepared cereals (especially raisin and bran mixes), dried bread crumbs, pasta, and many other grain-based products.

Control: Where food is stored in the home, an alternative to chemical pesticides is always preferred. The following suggestions will reduce the number of pantry or stored product pests:

  • Inspect food and other pantry products from supermarkets, health food stores, and other suppliers when they are first brought home. Infestations can start anywhere including manufacturing plants, transport vehicles, warehouses and store shelves.
  • Repackage items that are bought in paper wrap, cardboard cartons, or cellophane when food-infesting insects have been a problem. This prevents insects in infested products from moving to uninfested packages. Long-term storage of food products, bird seed, dog food and dog biscuits increases the probability of infestation unless adequate containers are used.
  • Discard infested foods.
  • Keep foods in solid plastic or glass canisters or coffee cans with tight fitting lids or in the refrigerator or freezer.
  • Destroy insects by spreading dry materials (such as dog biscuits or pasta) on a cookie sheet in a slow (140°F) oven for at least 30 minutes or in the freezer at 0°F for a week. These processes kill insects that are present, but do not prevent reinfestation.
  • Special pheromone (sex lure) traps are available to trap Indian meal moth and warehouse beetles. Moth traps will attract moths within 10 feet and can be used to determine if an infestation still exists.
  • Remove cocoons of food moths that are found on ceilings of cupboards or where walls and ceiling meet.

Cabinet cleaning procedure: Empty kitchen shelves of all food. Remove and destroy shelf paper. Vacuum cracks and crevices in cabinets. Wash shelves with soap and water. Let dry. Lay new shelf paper. Return food to cabinet in tightly lidded, secure heavy plastic or glass containers.

Cellophane wrap and cardboard boxes are not secure. Caterpillars can chew through them or through the flaps that seal the cartons. Food in cans or purchased in glass containers is not at risk and can be stored without repackaging.

Biological A braconid wasp parasitoid (Bracon hebetor) may be present, but does not control infestations.
Cultural Find and discard infested products (best4 )
Do not restock large amounts of pantry products until infestation is controlled
Repackage cellophane or cardboard boxed foods into glass or solid plastic containers
Mechanical/Physical Remove cocoons by vacuuming
Pheromone pantry pest traps (for monitoring, not control)
Store food in 0ºF freezer for 4+ days to kill all stages
Thoroughly clean cabinets, closets, and other food storage areas
Swat moths
Chemical Pyrethrin is labeled for control. This is generally not recommended in favor of other controls.