Flour moths are kitchen pests that are found not only in flour, but in other grains, mixes, dry pet food, and a number of other products. The most common are the Indian meal moths, or Plodia interpunctella, which are also known as grain moths and pantry moths. They are small, approximately 3/4 inch (1.9 cm) long, and light brown or gray in color with powdery wings. The larvae are tiny and look much like maggots crawling under thin webs.
When an area becomes infested with flour moths, the larvae is usually noticed first. Female moths lay up to 300 eggs in or near grains that the larvae can feed on as they hatch, and they quickly colonize in these products. Mature larvae spin cocoons and will emerge as adult moths in about 6 to 8 weeks under perfect living conditions. The moths will only live for about a week.
Flour moths seldom cause significant damage to whole grains. Instead they prefer processed foods such as cereals, pasta, and powdered milk. The larvae feed on the same types of food, though they tend to infest drier foods, while adult moths prefer items with more moisture. These can usually be found in basements or other damp areas. The larvae can chew through cartons, boxes and even cloth and have been known to destroy entire warehouses of grain products.
Food that is infested with flour moths should be discarded. They not only damage these products by simply feeding on them, but by leaving behind pupal casings, larvae skins, webbing, cocoons, dead moths, and their fecal matter. Food that is infested with flour moths may also have an off taste or unpleasant odor.
The only way to completely eradicate flour moths is by discarding all kitchen products that they have invaded. Insecticides will not kill moths or larvae living inside boxes and wrapped foods, and most are not recommended for use in areas where food is stored or served. Flour moths can also be killed with a heat treatment, although this is not always possible. In addition, most food products that have been heated should be served immediately to avoid spoilage.
Pheromone traps are another way to get rid of flour moths. They can be placed in the area where these grain moths are problematic, although they will only attract and kill the male moths. Exposure to cold will kill the moths in all stages of growth when the infested products are placed in a freezer for seven days. All of the insect parts and their fecal matter will still be present, however, so it's best to just discard infested foods.