Moth Myths

Pin-sized holes in a handknitted sweater, lost weft threads on a tapestry, or the powdering and eventual loss of a carpet can all be caused by one thing: clothes moths. There are thousands of species of moths in the world, but only a few will eat textiles. It is the larvae that cause the damage; as adults, the moths do not harm textiles because they cannot actually eat. The main species of concern are the casemaking clothes moth (Tinea pellionella), and the webbing clothes moth (Tineola bisselliella). As adults, both moths are approximately ½ inch (1.3 centimeters) long. The casemaking clothes moth (also called case-bearing) is a mottled light brown, and the webbing moth is straw-colored. The easiest way to tell them apart is by examining the textile damage caused by their larvae.

From Eggs to Moths

Like butterflies, moths hatch from eggs into caterpillars. The small caterpillars or larvae of both species of clothes moths are white with brown heads. They feed on proteins found in silk, hair, fur, and leather but have a particular attraction to wool. Casemaking larvae build a silken tube around themselves and drag it along as they consume their food source. Often, the case will take on the color of the textile they are eating, which makes them more difficult to spot.

The larvae of the webbing moth leave white silken webs all over a textile. Both types of larvae create holes and threadbare spots, and they can completely consume a woolen object if they are not treated. With such destructive creatures commonly found in homes, it’s unsurprising that humans have devised numerous ways to discourage them. But are these methods effective, or are they simply based on myths?

Strong Scents

Many traditional methods of preventing moth infestations center around aromas. People would often place sachets of scented plants such as lavender, eucalyptus, and rosemary among their textiles. Hope chests were often made of fragrant cedarwood to protect the garments that young women saved for their future marriage.

Some studies indicate that strong smells do dissuade moths. The terpenoid compounds from lavender, eucalyptus, and rosemary seem to disrupt the nervous and digestive systems of some moth larvae (see note 1). However, these larvae are not closely related to the species that attack wool fibers. The plant compounds may help eliminate existing adult moths, though, and prevent the introduction of new ones, but more research is needed to determine how effective these remedies are.

However, this method has some risk. If the scented plants or oils come in direct contact with a textile, they may cause damage. Cedar is particularly known for this. Wood becomes more acidic as it ages, which can cause yellow stains, brittleness, and weakened fibers. Cellulosic fibers, such as cotton and linen, are particularly affected by this, but proteinaceous fibers, such as silk and wool, can also be damaged by acids (see note 2).

Another issue with this moth-deterrent method is that the fragrance of the plants dissipates over time. Sachets of lavender need to be replaced and cedarwood must be sanded down to maintain its scent. This is easily done but also easily forgotten, which could be disastrous if it is your only method of preventing a moth infestation. If you want to try this natural method of moth prevention, make sure the scent-producing substances are not directly touching your textiles, replace them regularly, and frequently inspect and clean your objects.

If used carefully, lavender sachets can deter moth infestations. Photo by Conger Design

Extreme Temperature

Many websites claim that subjecting your textile to extreme temperature will kill moth larvae. Technically this is true but not very practical for the average person, and it can cause damage to your object. Exposure to high temperatures of 104°F (40°C) has been found to kill the larvae of the webbing clothes moth (see note 3). However, it can be difficult to safely raise an object’s temperature without causing damage from low relative humidity. The textile may become desiccated, making the fibers inflexible, brittle, and weak.

Many people recommend ironing a moth-infested textile to raise its temperature. However, directly ironing wool can cause the material to change its appearance and become shiny. It may also be difficult to penetrate the interior of a thick textile with enough heat without damaging the exterior. In addition, this method only works on flat textiles, not on three-dimensional ones, such as spinning fiber or a stuffed animal.

Sustaining a textile’s temperature below −4°F (−20°C) for a minimum of 15 hours or more has been found to kill the larvae of the webbing clothes moth. However, this is below the temperature of an average home freezer. Moth larvae are amazingly hardy and can survive to eat your textile another day if they are not exposed to a low enough temperature for a long enough period of time. Other materials found on textiles, such as sequins, beads, metal threads, ceramic buttons, etc., can also be damaged by freezing, and lowering the temperature can create harmful condensation. Textile conservators do treat moth-infested objects by freezing them, but for the reasons mentioned, this method is best done by a professional.

Like Moths to a Flame

Is light the key to protecting textiles from moths? Although adult moths are attracted to light, general wisdom is that moth larvae shy away from it. It is true that larvae will avoid bright lights but light won’t keep moths at bay. Unless your textile is very thin, the larvae will simply burrow through the object to avoid the light. The light will not end an infestation; it will just encourage the larvae to hide out of sight on the underside of an object.

Using light to protect a textile from moths is also trading one problem for another. All fibers are damaged by the ultraviolet radiation found in light. Wool can become yellowed, inflexible, brittle, and more easily damaged by chemicals with repeated exposure to light. Any dyes present on the wool can also begin to fade. Moth larvae may not like light, but textiles are damaged by it.

Although light is not helpful in preventing a moth infestation, it can help you spot them. Moth larvae are small and easily overlooked. An efficient way to check for larvae is to shine a light on the underside of an object such as a carpet and look for movement. If there are any larvae present, you will probably notice them wiggling to avoid the light.

Prevention and Good Housekeeping

Having moths in your home does not necessarily mean that it is dirty, but poor housekeeping can make it easier for moths to multiply. By altering some of your cleaning habits, you can make your home inhospitable to moths and decrease their numbers. Moths thrive in environments with dust, dirt, and crumbs because they eat these substances in addition to wool. By removing these food sources, you will make your home less attractive to moths and reduce their spread.

As already noted, moth larvae love to hide in dark, undisturbed places. By cleaning little-used nooks and crannies, you may discover larvae in spots you may have otherwise missed. The underside of a wool carpet is one of the spots where I most often find moth damage. A carpet can be a plentiful source of food that doubles as a dark undisturbed place in which to grow. For this reason, it is a good idea to vacuum the undersides of rugs on a seasonal basis and check any similar dark, frequently undisturbed locations, such as your yarn stash, for any unwanted admirers.

By practicing scientifically based moth prevention and avoiding myths, you will reduce the likelihood of moths damaging your textile treasures. However, sometimes woolen objects still get damaged by clothing moths. If you have a textile treasure that has been infested or damaged, contact a local professional textile conservator to learn how to protect your object from further harm.

Interested in learning more textile myths? This article and others can be found in the Summer 2023 issue of PieceWork.

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Notes

Ben Slimane Badreddine et al., “Chemical Composition of Rosmarinus and Lavandula Essential Oils and Their Insecticidal Effects on Orgyia Trigotephras (Lepidoptera, Lymantriidae),” Asian Pacific Journal of Tropical Medicine 8, no. 2 (February 2015): 98–103.
Ágnes Tímár-Balázsy and Dinah Eastop, Chemical Principles of Textile Conservation (Oxford: Butterworth-Heinemann, 1998).
Chemical Principles of Textile Conservation.