The commonly encountered clothes moths in a structure are the webbing clothes moths (Tineola bisselliella) and case-making clothes moths (Tinea pellionella). In the Midwest, webbing clothes moths are more frequently found indoors than the other species. These moths are about a quarter inch long with a light brown body and gold/reddish hair on the head. For untrained eyes, they may look identical, except that the case-making moth has darker wings with three dark dots on the forewings and gray-brown hair on the head. Clothes moths are known to breed in wool clothing, fur, hair, skins, feathers, silk, and other animal products. They also dwell in rodent dens as well as nests of birds or wasps. Fortunately, they do not infest cotton. The larvae of these little moths can be destructive pests in the museum, taxidermy places, and where expensive natural fabrics are found. Treating the adult moths alone will not provide control. To be successful, locating and destroying the larval breeding is a must along with monitoring.
Like usual, start with proper identification of the encountered bug before treatment; otherwise, liability, unhappy customers, as well as loss of profit and reputation are a few of the consequences. Once the identification is confirmed, find and remove the larval breeding source(s). Since clothes moth larvae feed on animal-made fiber, carefully inspect all cracks and crevices near or on carpets and rugs, furniture, mounted animals, and dark, undisturbed areas such as closets and attics. Once the source is found, it should be removed and treated.
Infested items that cannot be cleaned need to be sealed tightly in plastic bags and properly discarded in a trashcan/dumpster outside the building. If clients elect to keep these items, another option would be to place them in a hot dryer for 30 to 60 minutes; it is the responsibility of the customer to determine whether the heat can damage the articles that need to be heated. Clothes moth larvae and pupae can tolerate extreme cold. According to Chauvin and Vannier (1997), the super-cooling point (remaining unfrozen) for larvae and pupae is -13 degrees Fahrenheit. Therefore, if cold treatment is the only option available, place clothes and small fabric in polyethylene bags, squeeze all air out to minimize condensation, and then deep-freeze the materials for at least two weeks at temperatures below -13 degrees Fahrenheit. In addition, you can advise the customer to thoroughly vacuum and clean rug pads, under heavy furniture, and carpets, especially around the edges. Vacuum contents also need to be carefully discarded in the same way as the infested items mentioned above.
Once the larval breeding source is located, before using pesticides, make sure that clothing and personal belongings are removed from the area to be treated. Use a mixture of residual insecticides with an insect growth regulator (IGR) or a chitin synthesis inhibitor to treat all cracks, crevices, and voids in closets, under baseboard and molding, walls, and dark secluded hiding places. Apply spot treatments under heavy furniture, and under the edges of carpeting. Infested stuffed furniture and other similar commodities can be fumigated or treated with heat.
Monitoring after treatment is important to evaluate the treatment’s success. Setting realistic monitoring expectations requires an understanding of the life cycle of a webbing clothes moth, which relies extremely on the temperature, humidity, and nourishment conditions. For example, the development from eggs to adults may last 50 to 60 days, in optimal settings or up to four years when things are not suitable for growth (Smith and Whitman, 2007). Larvae hatch during the late summer and do not become adults until the following spring (Back, 1935). Pheromone traps that are specially designed for webbing clothes moths or case-making clothes moths can also be used to monitor the infestation or to evaluate the treatment. Note that webbing clothes moths’ pheromone traps do not attract case-making clothes moths unless the trap’s manufacturers confirm that the pheromones are made to attract both species; otherwise it will not work. These traps should be placed indoors in closets, floors, and areas where woolen, silk fabrics, furs, or items with feathers are stored. It is not unusual to catch webbing clothes moths in a pheromone trap up to nine weeks after treatment (the egg-to-adult development window).
Because prevention is better than cure, people at risk of webbing clothes moth infestations need to make sure that all animal-derived fabric materials and any items susceptible to the infestation by these pests are dry cleaned, laundered, or placed in a hot dryer for at least one hour before being stored for a long period. Additionally, keeping the relative humidity at or below 40 percent, as well as sealing all cracks, crevices and holes in the building, will generally create hostile environments for fabric pests and reduce their numbers indoors. Prevent wasps, birds and rodents from settling in or around the building, as these can be alternative sources of clothes moth infestations. Finally, keep monitoring. Inspect pheromone traps frequently and replace them every nine weeks to maintain protection, or as per the manufacturer recommendation.
Back, E. A. 1935. Clothes moths and their control. Farmers’ Bulletin, USDA No. 1353 (revised), 29 pp. Google Scholar
Chauvin, G., Vannier, G., 1997. Supercooling capacity of Tineola bisselliella (Hummel) (Lepdioptera: Tineidae): its implication for disinfestation. Journal of Stored Products Research 33, 283-287.
Smith, E. H., and R. C. Whitman. 2007. NPMA Field Guide to Structural Pests, 2nd ed. Fairfax, Va: National Pest Management Association.