Updated: Dec 27, 2019
Moth damage on a Kurdish rug being repaired
Insect infestation is a common and often reoccurring problem in home environments. Insects make no distinction between valuable textiles and utilitarian ones. They seek out opportune environments to infest textiles for shelter, reproduction, and in the case of some months and beetle species for food. The protein and moisture content of textiles such as wool are what these insects seek. Since these insects have no other source of hydration moisture content and humidity play an important part with infestations. Most household soils contain proteins, oils, and starches which are mostly hydrophilic (moisture loving) and elevate moisture level of proteins fibers. Therefore, Soiled textiles make for a more hospitable environment for infestation with higher moisture levels as well as additional sources of nourishment for insect larvae development.
The three most common insect infestations in wool textiles
Webbing Moths (Tineola bisselliella)
Webbing Moths are 5-7 mm long and golden in color are poor flyers and avoid light. The mature moths live for several weeks and lay eggs in dark undisturbed areas for example, under a sofa. The female can lay in excess of 100 eggs at a time and these eggs are barely visible to the human eye. When they hatch the larvae spin a cocoon to protect themselves from light and to provide adequate humidity control. They then consume protein fibers causing damage. The larval stage can last from several weeks to over a month at which point the larvae pupate into adult moths. Leaving behind a webbing material and small grainy excrement.
Casing moths (Tinea pellionella)
Casing moths are 7-8 mm when mature, golden in color and with dark spots on their wings. Casing moths spin a cocoon around their bodies. This casing is dragged around as they feed. Casing moths favor higher humidity than webbing moths and can tolerate cooler temperatures. Casing moths usually eat from the surface of a textile like a pile rug whereas webbing moths will borrow. Once mature they leave behind the casing which is slightly larger than a grain of rice.
Carpet beetles (Anthrenus sp.)
Adult carpet beetles are 2-4 mm small round and similar in shape to lady bug but smaller with a white, black, brown, orange shell. The larvae have black brown bristly hairs and typically eat in one area leaving round divots similar to small cinder burns from a fire.
Pest mitigation falls
into five strategies
Avoidance. Avoid conditions that promote insect infestation. Keep textiles clean with regular vacuuming and washing. Before storage, textiles should at a minimum be vacuumed and inspected. Although washing is highly recommended and subsequent wrapping in a breathable product such as Tyvek or Heavy Kraft paper to inhibit soiling and infestations.
Blocking. Block insect entrance to the home. Often infestations enter the home via an open window or newly acquired textiles infested with eggs that subsequently hatch and spread to other textiles. Consider through cleaning or moth treatment of new textiles before they enter a home environment. Open doors and windows that allow easy access to textiles should be minimized.
Detection. Regular inspection of textiles is important, this can be done during rotating or routine vacuuming with care inspect dark undisturbed areas under a sofa and with hanging textiles the back. Consider pheromone traps as a monitoring tool to determine when an infestation is present.
Confine. When an infestation is detected the infested textile should be removed from the home or confined (wrapped in plastic) to stop the spread of infestation to other textiles and treated soon as possible.
Treatment. We will restrict the topic to treatments done outside of the home. In many states, it’s illegal to perform on location pest control services without a pest control license.
Freezing is an effective method to control an active infestation. It’s generally recognized that temperatures of -20 C. (-4.F) are needed to ensure eggs are killed and for a period of one week. Often textiles are allowed to thaw for several days and multiple treatments or freezing and warming to shock any survivors of the initial freeze. Wet textiles should be dried first before freezing to reduce the possibility of damage from water ice expansion and crystallization.
Temperatures of 45 C. (113 F.) has been shown to kill insects in all stages of development in a matter of several hours. It’s important that the textile temperature reaches these temperatures, not simply the room the textiles are in. The two-hour treatment should begin when the textiles have reached 45C. (113F.)
The use of washing as a treatment has shown minimal effectiveness by itself. However, hot water 150. F and steam particularly, with pretreatment of insecticides are effective but one risks color run, shrinkage and felting so this method has not been investigated to its full extent.
Dry cleaning solvents are effective particularly when combined with heat the limitation is the size of textile and nature and condition of the textile to be treated.
Moth ball/crystals (Naphthalene, para-dichlorobenzine).
Work in enclosed environments in high concentrations. Carpet beetles are not as sensitive as webbing & casing moths. Additionally long term exposure can cause staining and discoloring with some textiles and the odor permeates textiles which is objectionable to some and requires washing to remove.
Pesticides are effective at dealing with adult moths and larvae but not unhatched eggs. As such multiple treatments are required.
Commercial chemical treatments
Microban is often used commercially to treat moth infested rugs. Applied to the front and back of the rug which is then typically rolled up and placed in a plastic tube for 24 hours and subsequently dusted and washed this has been shown to be effective.
Neem oil is not a pesticide in the classic sense. It does not directly kill insects rather it disrupts insects life cycle by blocking and altering hormones from working properly. Insects forget to eat, mate and stop laying eggs. While effective and safe Neem is slow to work and some find the smell and oily residue objectionable
What doesn’t work.
The list below are examples of methods which may provide some ancillary benefits but do not stop pest infestations. These are best used in addition to proven mitigation methods above.
-Cedar oil, wood blocks or shavings
-Airing out textiles in sunlight
-Tobacco, Lavender or other dried plant herbs, oils or leaves rolled in with a rug.
-Wrapping in newspaper
Emphasis should be placed not only on treatment of infested textiles but monitoring, preventive strategies. These include weekly vacuuming, visual inspection, and timely washing of textiles and wrapping textiles prior to storage.