Guide · For the trade
Moths in wool rugs: the signs, what to specify to prevent them and what to tell the client
Moths in wool rugs are the larvae of two small clothes moths, the webbing clothes moth and the casemaking clothes moth, which eat the keratin in wool and leave bald patches, loose fuzz and sand-like droppings, nearly always under furniture or along a wall where the rug is dark and undisturbed. Prevention is in the spec and the care sheet: mothproofed wool where the mill offers it, quarterly vacuuming under the furniture, professional washing every three to five years and never storing a rug unwashed. A rug already infested goes to a rug washer for an immersion wash and treatment, and a rug restorer reweaves the holes.
This guide is for the designer who specifies wool rugs and carpet and gets the call a year later, or wants to not get it. It covers which insects do the damage, the first signs, what to write in the spec, the care sheet to hand the client, and what to do once moths are found. The wool rug shedding guide covers the fuzz that is not moths.
What are carpet moths, and what type of moths eat wool?
Two species do almost all of it in the United States. The webbing clothes moth, Tineola bisselliella, is a buff-colored moth 1/4 to 1/2 inch long that avoids light; its larva is a 1/2 inch cream caterpillar that spins silky webbing over the pile. The casemaking clothes moth, Tinea pellionella, is darker, and its larva drags a small fabric case the color of the rug. Both are called carpet moths in the trade. The adults do not eat; the larvae do, and only animal fibers: wool, silk, mohair, alpaca, cashmere, feathers and fur. Carpet beetles, which are not moths, do the same damage. The moth the client sees at a lamp is not the problem; the moth that eats a rug is small, pale and rarely seen.
The first signs of moths in wool rugs
| Sign | What it looks like | What it means |
|---|---|---|
| Bald or thinned patches | Pile worn to the foundation in an irregular shape, at a corner or under a sofa | Active or past feeding; check the back for the same shape |
| Loose pile fuzz | Tufts of wool lying on the surface that come off in the hand, foundation intact | Larvae cutting the pile at the base; usually the earliest sign |
| Sand-like grit | Fine granules in the color of the rug, on the pad or floor under it | Frass, the larvae's droppings, dyed the color of the wool they ate |
| Webbing or tubes | Silky threads or small cocoons in the pile, under the rug or at the fringe | Webbing clothes moth, active |
| Small pale moths | 1/4 to 1/2 in, flying low or crawling near the rug or a closet | An adult population; the larvae are nearby |
Damage is found under things and at the edges: under a sofa that has not moved in a year, along the wall side of a rug, and on the back of a hand-knotted rug, which shows it first. Rugs rolled in a closet or a garage are the most common site of a serious infestation, and so is wall-to-wall wool under heavy furniture that is never moved.
What to specify to prevent moths in wool
Mothproofing is an insect-resist agent applied to the wool at dyeing that binds to the fiber and lasts the life of the carpet through normal cleaning. Most New Zealand and British wool broadloom is treated at the mill, and the spec sheet says so when it is; Fabrica, for example, states "this product is mothproofed" in the product notes of its wool lines, and we check the sheet for any wool broadloom on request. Hand-knotted and hand-tufted rugs are usually washed, not treated, so prevention there is in the care. For a rug that will be stored for part of the year, or a second home that sits closed, specify a mothproofed broadloom cut and bound rather than an untreated hand-made piece, or a wool-free construction. The wool filter lists the 2,457 wool styles across the mills; ask us which are mothproofed at the mill.
The care sheet to hand the client
- Vacuum the whole rug weekly, beater bar off on a hand-made rug, and vacuum under the furniture and along the walls at least every three months. Light and movement are what moths avoid.
- Lift the furniture that sits on the rug twice a year and vacuum the rug and the pad underneath.
- Rotate the rug once a year so no edge stays against a wall in the dark.
- Send a hand-made wool rug for professional washing every three to five years, sooner in a house with dogs. Immersion washing kills eggs and larvae; surface cleaning does not.
- Never store a wool rug unwashed. Wash it, wrap it in breathable paper or cotton, not plastic, store it off the floor in a lit, dry space, and check it every six months.
- Pheromone traps in closets show whether moths are present; they are a monitor, not a cure.
What to do when moths are found
Do not treat it in place with a spray and hope; a sprayed rug is still full of eggs under the pile. Send the rug to a professional rug washer for an immersion wash with a moth treatment, which kills every stage; a small flatweave or a bound mat can be bagged and frozen for 72 hours at 0 F and then washed, but a 9x12 hand-knotted rug goes out. Vacuum the floor and baseboards where the rug was, replace the pad, and check every other wool textile in the room. The holes are repaired by a rug restorer who reweaves the pile on the existing foundation; a wall-to-wall wool carpet is patched from the 2 to 3 square yards we recommend holding from every wool broadloom job. A wool rug in a lit room with weekly vacuuming, furniture that moves and a wash every few years rarely sees a moth, and moth risk is a care item, not a reason to specify polyester.
Questions designers ask
What are carpet moths?
Two clothes moths, the webbing clothes moth and the casemaking clothes moth, whose larvae eat wool and other animal fibers. The adults are small, pale and avoid light; the larvae are 1/2 inch caterpillars that cut the pile at the base and leave frass and webbing. Carpet beetles cause the same damage and are treated the same way.
What is the disadvantage of 100 percent wool carpet?
It is an animal fiber, so it can be eaten by moths and carpet beetles if it is left dark and undisturbed, and it costs more than a synthetic. Against that, wool is self-extinguishing, hides soil, recovers from crushing and takes dye better than anything else. Mothproofed wool broadloom removes most of the first concern.
Does vinegar kill clothes moths?
Not in a rug; it will not reach the base of the pile. Cedar and lavender repel adults mildly and do nothing to larvae. What works is immersion washing with a moth treatment, freezing for small pieces, and mothproofing at the mill.
How do you know whether the damage is moths or wear?
Wear is where the client walks and is even across the lane; moth damage is where no one walks, in an irregular patch under a sofa or along a wall, with loose fuzz, grit and webbing, and it shows on the back of the rug in the same shape.
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