Indian Meal Moth

Overview:

The Indianmeal moth, also spelled "Indian-meal Moth" (IMM) (Plodia interpunctella (Höbner)) is among the most important and common stored product pests in the United States. The infestations of IMM are not limited to pantries inside homes, but also, they can thrive in grocery stores, food processing plants, grain storage facilities, and other areas where food is available. Although, the adult moths do not feed, they reproduce and lay eggs on various food materials, including but are not limited to, flour, cereal grains, seeds, dried fruits, pet food, spices, ornamental products, etc. This pest is commonly found infesting coarser grains of flour, such as whole-wheat flour, and cornmeal; however, larvae are general feeders and are the ones that cause the most damage by their feeding and breeding habits. Besides consuming food, larvae also leave behind their feces, shed skins, silk threads and other debris. In addition, they are capable of chewing through thin plastic bags and cardboard.

Facts:

• The IMMs are worldwide-distributed pests, originally from South America.
• Asa Fitch, the early New York sate entomologist, actually is the one who invented the common name as he noticed the infestation of this insect on the Indian corn.
• A study has shown that the exposure of IMM to certain wavelengths of sound during the egg-laying period reduces their reproduction by 75 percent.

Identification:

• Adults are about 3/8-inch long with a 5/8 to 3/4-inch wingspan.
• Adults are easily distinguished by the color of their wings. The outer half of the wing is reddish-brown colored; whereas, the inner half of the wing is grayish-white colored.
• Eggs are small and grayish to dirty white in color.
• The mature larvae are about 1/2-inch long and dirty white, pink brown, or light green. The head and top of the first body segment behind the head are reddish brown, yellowish brown depending on its food.
• Pupae are reddish-brown and about 3/8-inch long. They are enclosed inside silken cocoons.

Biology:

• Like other moths, the IMM goes through a complete metamorphosis (four different life stages: egg, larvae, pupa and adult).
• Females lay between 39 - 409 eggs, with 128 being the average.
• Eggs hatch in 2 to 17 days.
• The optimal temperature range for development is 79 to 84°F.
• Larvae will mature in about 5 weeks.
• Larvae feed and produce a silk like "webbing" material throughout the infested areas and products.Food materials may be completely matted with this webbing if the infestation is heavy.
• In order to pupate, larvae move away from the infested products and spin cocoons along ceiling/wall joints, on top of and under cabinets and shelves, in the folds of cardboard boxes or cartons, and nearby cracks and crevices. At this time, homeowners generally start to notice the presence of the IMM problem.
• The pupal stage lasts about two weeks.
• The newly emerged adults mate and lay eggs about two to three days later.
• Adults live a relatively short period of time (2-30 days) and cause no damage. They simply mate, lay eggs and die.
• An entire life cycle can be completed within four weeks under favorable conditions.
• There are between 4-8 generations of IMM per year depending on the temperature, humidity and food conditions.

Habits:

• While the adults are weak flier, they are mobile and capable of finding suitable food resources. When flying, they fly in an irregular, zig-zag pattern.
• Adults are chiefly night flyers, becoming most active at dusk.
• They are attracted to light, resting on walls and ceilings, can be attracted to TV's. During the day, they prefer to rest on walls, ceilings, boxes, or in poorly lighted areas.
• As aforementioned, adults do not feed, while larvae are general surface feeders. Which means the larval feeding is confined to the surface of the stored product. But, however, in small, loose food packages, larvae may spread to various layers of the infested product.
• The fully mature larvae usually crawl out of their food habitat and construct cocoons to pupate. Cocoons could be found in cracks, crevices, where the wall and ceiling meet, top of the cupboard etc. Larvae may also pupate on the food surface and bin walls.

Treatment:

Prevention

• Inspect all suspected materials before storing or placing into cupboards. If the source of the infestation is not in the kitchen or pantry, then you need to check closets, storage rooms, dresser drawers or other areas where jewelry or decorative items made with nuts, ornamental corn, various grains, seeds, dried fruit, etc. may cause an infestation; also keep in mind where children may have spilled any food products.
• Avoid buying old food products and use FIFO (first in-first out) strategy.
• Always store food in insect-proof containers with tight-fitting lids. Transfer products that are packaged in paper, cardboard, or plastic bags into tight sealing containers such as Tupperware, Rubbermaid, etc.
• Keep highly susceptible food, such as coarse flour in the refrigerator or in the freezer. If at all possible, foodstuffs need to be stored in "cool" cabinets, avoid storing susceptible products in cabinets next to or above the stove and refrigerator.
• Food should not be kept or stored for more then two months (if kept in cold storage, you can store it longer).
• Immediately vacuum all spilled food materials.
• Clean shelves with soap and hot water, allow to dry and cover with clean, fresh paper or foil before placing any food or cooking utensils.
• In order to reduce the population development of stored product pests, including the IMM, keep the moisture content of processed goods low. This can be simply accomplished by facilitating a proper ventilation system inside a storage area.

Physical Methods 

• Heat or cold treatments: Place infested food in a freezer at 0°F for four to seven days or heat at 140°F for one hour or 120°F for two hours. To avoid damaging certain items, check the product's label before any heat/cold treatments, i.e., seeds saved for planting may have the germination reduced after superheating or cooling.

Mechanical methods

• Remove and destroy all cocoons by vacuuming. Pay close attention to cracks and crevices.
• Remove the eggs and feeding larvae by carefully discarding infested materials outside the building.
• Install insect light traps to capture the flying adults. Pheromone traps are also commercially available to capture the flying males on sticky boards. "Traps alone are "monitoring tools" for early detecting, monitoring and pinpointing the hot spots of the infestations. They are not a control method, but they can help in reducing a few flying adults".

Chemical Methods

• Before treatment, properly discard all infested products outside the building and remove food, water and clothing materials from areas to be treated.
• In heavy infestations, apply a space treatment with an EPA approved non-residual insecticide to knock down the adult populations in warehouse and food processing facilities. However, fogging alone will not solve the infestation problem.
• Keep in mind that the larvae, which are in pupae stage, have moved away from the food source, therefore, target all feeding, breeding and harborage areas using EPA approved residual insecticides as crack, crevice and spot treatments in pantries, closets, baseboard, doorframes, window frames and other places where larvae could reside or hide. Carefully follow the product label directions.
• Apply a spot treatment to surfaces near food storage areas, in and around cabinets, under and behind machineries, appliances and furniture; remove shelf papers, and treat where food IS NOT present.
• If applicable, apply a perimeter treatment to prevent flying adults coming from outdoors.
• During the treatment, no people, food, or pets should be present in the area to be treated. Fish tanks should be covered and temporary the air shut off. Plants will not be affected.
• Do not enter the treated area or use before all applied pesticides are dried.
• Anyone with a respiratory condition should notify property manager and the Adam's Pest management Professional.
• Follow prevention methods and keep monitoring to minimize the periodic space treatments.
• Keep monitoring.

Frequently Asked Questions:

Q: I have a moth infestation in my house. The Adults seemed to be more active at dusk. Are they Indian meal moths or clothes moths?

A: The IMM larvae are usually yellowish, greenish, or pinkish in color with brown heads. They have five or six ocelli (eyespots) on each side of the head; Clothes moth larvae have either one pair or none. The adult clothes moths have no rusty brown or reddish colored scales on the tip half of the wing, and are generally smaller, additionally, IMM affect food products and not fabric.

Q: Do Indian meal moths transmit pathogenic agents that cause diseases?

A: No. They do no transmit or carry pathogenic agents.

Q: How did I get Indian meal moth?

A:  IMM usually are introduced into homes through purchasing already infested food materials, including pet food and birdseeds. Additionally, some adult moths do fly into buildings through open doors, windows, vents, etc.

Q: What do I do to get rid of Indian meal moth?

A: Find the source of the infestation, carefully remove or destroy it, and finally thoroughly clean infested areas.

Q: I have an obvious infestation of Indian meal moths, but I do not want to throw out my infested food. What could I do?

A: If you elect not to discard infested food materials, another solution could be accomplished by placing infested materials in a freezer to destroy all Indian meal moth life stages. But first of all, make sure that freezing process will not damage the infested food as some food products can be damaged during freezing. Next, properly bag infested food and freeze at 0°F for four to seven days or at 14°F for 10 days. Heating food products at 120°F for two hours or at 131 0°F for 30 minutes also can provide 100% destruction of IMM life stages. When above methods are implemented, you have added extra protein to your diet. However, some people would rather pour the food contents after heating or freezing into a large container and sift through them, or empty the contents into a strainer and sift. So either way is safe and can be easily implemented.