Extension News

The Case of the Clothes Moth

Note to media editors: This is the Garden Column for use during the week beginning May 29.

5/25/2009

By Laura Jesse
Plant and Insect Diagnostic Clinic
Iowa State University

I learned in my entomology courses that the clothes moth, once a well-known and common pest of fabrics in the home, is rarely encountered these days. This is because carpets and clothing are often made of synthetic fibers and so are not attacked by clothes moths, which prefer woolen items. So, I guess this means I am one of the rare and lucky homeowners to have a clothes moth infestation.

You would think as an entomologist I would quickly track down and eliminate the infestation. However, I am fundamentally a person who hates going through all the things I have stuffed into the back of various closets. Instead I watch the moths flitting around my bedroom at night and try to think if I have any wool items I would be really upset if they ate.

As a bit of background I should tell you that two species of clothes moths may infest woolens and other animal fibers. The casemaking clothes moth is more common in Iowa than the webbing clothes moth.

The name of the casemaking clothes moth comes from the silken tube, or case spun by the caterpillar and carried about wherever it goes. The 1/2-inch long case incorporates bits of fabric and is the same color as the fabric being consumed. Caterpillars of both species are 1/2 inch long and white with brownish-black heads.

The clothes moth caterpillar is the only feeding stage and therefore the only stage that damages fabrics. The caterpillar stage lasts for 1 to 3 months and the larva eats only fibers or materials of animal origin. These include woolen rugs and clothing, hair, fur, feathers, taxidermy mounts and felt. I am pretty sure mine must be eating wool since I can't remember owning any fur or feather items, and I am pretty sure I would know if I owned a taxidermy mount – there are limits to what I can stuff into the back of a closet.

Clothes moth caterpillars prefer to feed in protected locations such as under collars, inside hems, on the backside or in cracks at the edges of woolen carpets, under furniture and inside storage containers. Several years ago I found what seemed to be the source, a wool rug I had rolled up and stored in the basement. The rug was completely destroyed and there were hundreds of caterpillars (the casemaking kind) and a whole lot of caterpillar frass. I discarded the rug last year, so now I am not sure where my current crop of adult moths is coming from.

I assume they are not feeding in the closet because clothes moths really do not infest garments or items that are used or moved regularly because the caterpillar would easily be dislodged. I check the bottom of my closets for frass and discarded cases, but so far have had no luck. I commonly see the moths in the bedroom, but they could just be attracted to the lights. The adult moths are about 1/4 inch in size and are a sort of attractive shiny silver color. I usually see them flying a few feet above the floor.

If I could find where the caterpillars are feeding control would not be difficult. If the item is salvageable it can be dry-cleaned or washed and dried at a high temperature. Insecticides are not really necessary. Vacuuming out the area thoroughly to remove any wandering caterpillars and then storing wool items in tightly sealed containers will work well.

I think the most important thing is to check items several times a year and provide that disturbance the moths don't like and catch any infestation early before too much damage is done. Do not be like me and watch the moths fly around for months before deciding to go on the search.

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Contacts :

Laura Jesse, Plant and Insect Diagnostic Clinic, (515) 294-0581, insects@iastate.edu

Del Marks, Extension Communications, (515) 294-9807, delmarks@iastate.edu