[Pest Spotlight] Clothes Moths

There are two primary species of clothes moths that attack fabric: the webbing clothes moth, Tineola bisselliella (pictured above), and the casemaking clothes moth, Tinea pellionella. These omnipresent moths are worldwide in distribution and are a serious pest in the United States and Europe.
SIGNS OF INFESTATION. Clothes moths are unique insects that can be readily identified by their physical characteristics and behavior.
  Clothes moth larvae are the destructive phase of this insect, producing a “sleeping bag-like” case that is easily detected on fabric. Casemaking clothes moth larvae are identified by the black patch on their head, whereas webbing clothes moth larvae have a brown patch. Adult clothes moths skip around on the ground or on carpet. They hide and lay their small eggs in cracks and crevices.
  The adult females emerge from the pupal stage to a waiting male, mating within 24 hours. The females then fill up with eggs and become flightless. This means the females and her eggs can be found in cracks and crevices, and near the floor in dark, secluded areas in closets, museum collections, basements and other undisturbed areas where temperatures are neither too hot nor too cold for their survival.
They are often found in woolen materials. They prefer used or raw wool that has mineral deposits on them (e.g., perspiration, urine, etc.). Old military uniforms, woolen carpets, and woolen materials of all sorts will attract these moths, as will the feathers and debris associated with pigeons, and paper wasp and bald-faced hornet nests.

CASE STUDIES. Reviewing case studies is an effective way for pest control technicians to learn more about the biology, behavior and control of clothes moths. Here are a few case studies designed to test your pest management skills:

Case Study #1. Recently a large home in New England was experiencing a casemaking clothes moth outbreak. Pheromone traps placed in the home led the pest management professional to a room with numerous carpets. The carpets were inspected and cleaned and placed back in the home. Despite the homeowner’s best efforts, the traps still captured additional casemaking clothes moth adults. This went on for more than a year, causing many sleepless nights for the pest management professional.
Finally, we discussed the problem over the phone again and I asked if the homeowner had any antique furniture in the home. The answer was, “Yes, some 18th-century chairs and tables.” I then asked if the chairs had horse hair in them.
After inspecting the bottom of the chairs for signs of moths and frass, the problem was solved. It turns out, the chairs in this $5 million New England mansion did in fact use horse hair for cushioning. The horse hair chairs proved to be an ideal food source and harborage site for this fabric and animal protein pest. The frass was dropping out of the chairs and onto the carpets, resulting in an ongoing infestation.

Case Study #2. Museum objects are often attacked by clothes moths. The world famous Childrens’ Museum in Indianapolis once had a widespread problem with the webbing clothes moth. After weeks of inspection, pheromone detection and tearing the third floor apart high and low looking for the clothes moth “nova,” or infestation source, one day a hidden closet was opened that was being used as a storage area. Inside two large black plastic trash bags located inside the closet was raw wool that volunteers had used on a spinning wheel demonstration three years before! The clothes moths found the bags of raw wool. This became the nova that led to a population explosion of this fabric pest in a museum full of precious items.

Case Study #3. Many people find bald-faced hornet nests to be attractive as display items. They bring them in from the outdoors when the leaves fall from the trees and place them in their house, museum or business to show the beauty and architectural prowess of these insects. What the homeowner or other unsuspecting layman doesn’t know is these nests contain dead hornets from the final freeze of the year, and this protein is the food that scavenger insects like Dermestids and clothes moths find attractive.
Hornet nests are potential sites for clothes moths to hide and breed over time. One nest at the Field Museum in Chicago was so infested with clothes moths that the moths completely eliminated it into dust in an undisturbed box in storage.

INSPECTION. When inspecting for clothes moths, always look for the small sand-like pebbles in and around the infested area. These are fecal pellets commonly called frass. The frass falls from the area where the larvae are feeding, and it will take on the color of whatever the larvae have been feeding on (for instance, purple woolen carpet leads to purple sandy frass, chicken feathers yields white frass, etc.). Female clothes moths will also drink water, so placing a small saucer of water out will capture some of the female moths.
Understanding the biology of clothes moths is essential to performing a proper inspection. Clothes moths have one or two generations per year in the United States, and the spring flight is the larger of the two. Clothes moths are found in the greatest numbers from February through April in North America, less in the hot summer months, and are found again in the fall when the humidity rises again.
Pheromone traps are a valuable and easy-to-use tool for pest management professionals to incorporate into their control program when conducting an inspection. A new formulation of the clothes moth pheromone that captures both the webbing clothes moth and the casemaking clothes moth is available from Insects Limited, Inc., Westfield, Ind. The pheromone-baited trap for clothes moths is effective in locating male moth activity and for determining when clothes moth activity is reduced or eliminated. The moths are attracted by the pheromone and captured on the sticky trap.
Pheromone traps should be placed  year round and pheromone lures should be replaced every eight to 10 weeks. The pheromone traps pull from a 20 to 30 foot (7 to 10 meter) radius and one trap per closet is recommended. The pheromone lure is sensitive to sunlight and care should be taken not to leave the lures in hot service trucks or other storage areas above 90o F (31o C). The lure can be stored in the original packet for up to two years, and longer when refrigerated.

CONTROL. Clothes moths are sensitive to extreme temperatures, so “freeze them” or “fry them” whenever possible. Pesticides don’t need to be used in many cases. Winter is the time to recommend that your customers wrap their woolens, cashmere sweaters, mole hair jackets, trophy mounts, silk ties, and other suspect materials containing animal protein, and place them in the trunk of their car or in outdoor, unheated storage areas. They should be stored at freezing or below for one to two weeks.
These fragile moths are also sensitive to heat. If the object can take elevated heat, place it in the oven, microwave, or in a black plastic bag on the roof in the summer. Direct sunlight on a black plastic bag will produce 100-plus degrees (40º C). In many parts of the world, carpets are periodically taken outdoors to be “aired out.” The direct sunshine and movement of the carpets will control the clothes moths and allergy-ridden house dust mites.
Steam cleaning by a professional rug cleaner is another way to protect carpets and woolens. It is important, however, to eliminate the moths in the home prior to having carpets professionally cleaned or before returning the rugs and woolens to the structure.
If moths have destroyed a tiny area in a fine carpet, the cost of repair and matching the colors exactly can be more than the value of the carpet itself. Moth balls have been used for years with some success, but the smell of moth balls is unappealing to some people, so it’s not the preferred option. A pest management program that includes prevention, monitoring and low-impact control techniques will help control these storage pests.

CONCLUSION. Clothes moths can be difficult to detect, but pheromone traps can help you locate the source of the infestation and can also indicate how far the problem has spread. Once an infestation is confirmed, these pests can be controlled by disrupting their fragile living habits with either heat or cold, as well as with targeted applications of insecticide indoors.
Always start with the biology and behavior of the clothes moth. Find out what it likes and what it doesn’t like. Then offer what it doesn’t like, and it will leave or it will die.

The author, a board certified entomologist, is president of Insects Limited, Inc., Westfield, Ind., and a graduate of Purdue University. He can be reached at dmueller@giemedia.com.