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Indian Meal Moths

The most common household moth capable of indoor reproduction in Colorado, the Indian meal moth develops as a pest in a variety of foods commonly found in pantries.  The caterpillar stage is responsible for damaging susceptible food items, while adult moths are more of a nuisance.  Both stages can be found within infested homes.  Adult Indian meal moths are roughly 3/8 inch long with a dirty grayish-brown coloring.  Wing tips are rusty brown or bronze in color making it easily identifiable from other household moths.  Caterpillars are primarily cream colored, occasionally with yellowish-green or pinkish shades and a dark brown head.  Typically, caterpillars stay associated with food; however, full grown caterpillars which are approximately 2/3 inch in length may be seen seeking a place in which to pupate.  Three to four generations occur per year and may overlap causing all stages of development to be present at the same time.  Rate of development is dependent upon temperature and quality of food.  During optimum conditions caterpillars may become full-grown in as little as a month, although typically a much longer period of time is necessary.

Adults survive little more than a week after emerging from their cocoons as they do not feed during the adult stage.  This stage is strictly responsible for mating and laying eggs.  Activity is most commonly noticed from dusk through the night.  Females lay their miniscule sized eggs of around 200 on or near potential food sources.  The caterpillars that emerge immediately seek out food.  They are capable of chewing through plastic bags and thin cardboard.  For this reason, coarsely ground grains and cereal products are commonly infested.  Other items typically include dried herbs and fruits and nuts as well as pet foods such as bird seed, dry dog food and flaked fish food.  In addition to food items, decorative items such as dried flowers or items containing seeds may also be infested.  Silk produced by the caterpillars loosely binds food fragments and is often an indication of an infestation.  In undisturbed containers, feeding is primarily done near the surface with little burrowing.  Once fully grown, the caterpillars seek out a place to pupate for their transformation into the adult stage.

Although Indian meal moth infestations can be eliminated within the home, reinfestation is possibly through the accidental introduction of infested foods.  The first and most critical step in eradicating these pests is to locate and identify all sources of the infestation.  The presences of caterpillars or the loose silk webbing are typically the first keys to knowing which products are infested.  Residents should evaluate all food items for potential infestation especially produces that have been stored for an extended period of time.  Pet food and decorative pieces should also be checked for activity.  Infested sources should be immediately disposed of or treated with heat or cold.  Heat requires an oven temperature of 120-140 degrees for at least 20 minutes.  Damage to the product may occur.  Cold treatments involve placing items in a deep freeze for two to three days.  Areas where food spillage may occur should be thoroughly cleaned including cracks and crevices.  Foods should be stored in plastic or metal containers with tightly sealed lids.  Denying the Indian meal moths’ access to all food sources should be maintained for a minimum of one month in order to ensure that all stages are eliminated.  Insecticidal control is limited due to areas of infestation.  Pheromone traps are available; however they only attract the male moths.  Cleaning and discarding infested products typically provides a majority of the control for this pest.