Mystery fabric pests

|  March 1, 2013

Have you ever had a customer phone in a treatment request for clothes moths based upon small holes in clothing or draperies, and when you inspected the items in question, there was no evidence of clothes moths — or other fabric pests — to be found?

This is a situation that my co-workers and I encounter several times a year, and I have heard similar stories from technical directors and managers associated with other pest management companies. One would think that a customer who learns these holes were not made by insects or rodents would be somewhat relieved, at least to be able to eliminate the possibility of pests infesting their garments or other fabric items. However, this usually is not the case. The typical response from the customer is, “Well, there must be a pest, because there is no other explanation for these holes.”

Finding the evidence

Perhaps the most important thing a pest management professional (PMP) in this type of situation can do is ensure that no pest organism is responsible for the holes in question. How can we be sure? For starters, most pests leave behind evidences of having been active in an area. For example:

■ Rodents such as house mice leave behind droppings and urine stains detectable with ultraviolet (UV, or black light) lamps.
■ Webbing clothes moths leave behind silken trails and frass in the vicinity of the larval chewing damage to fabrics; so even if no actual larvae or moths are present, the silken trails and minute frass pellets ought to be visible.
■ Casemaking clothes moth larvae create small, elongated cases for themselves. These mobile shelters, constructed from silk and debris (including frass), are visible to the naked eye and generally remain on the infested item after development is complete.
■ Carpet beetles and other dermestids usually will be present in the larval or adult stage, alive or dead — somewhere near the infested item, if they are to blame. Often the cast skins (exuvia) of the larvae will be on or near the infested item. A word of caution is warranted here, however: The mere presence of a carpet beetle or two on a nearby windowsill or other surface does not confirm that species as the destructive agent responsible for the holes. Carpet beetles are present in most residences and commercial buildings, breeding in numerous sources of dried animal protein (the dry remains of rodents, nuisance birds, insects, pet hair, etc.) that may be present in structural voids and other undisturbed places.
■ Silverfish will chew holes in fabric on occasion, but sightings of silverfish usually will be frequent in close proximity to the damaged fabrics.
Consider the source

How else can we be sure that pests are not responsible for holes in fabric? For an insect to develop, it needs to consume digestible food. Are synthetic fabrics of any food value to insects? Will an insect feed on polyester, acrylic, acetate, rayon or nylon fibers?

Photo: iStock

Photo: iStock

It depends. Is the weave a blend of natural and synthetic fibers? If wool is present, that might stimulate certain fabric pests to nibble holes. Are there any food or beverage stains on the fabric item? Studies have shown that fabric pests prefer to feed on food-stained fibers because of the additional nutrients present.

The same pest preference applies to perspiration stains on fabrics. To some insects, our sweat is equivalent to a sports drink because of the electrolytes found therein. When someone decides to put a once- or twice-worn garment back in the drawer or closet because it still looks clean, there is always a chance that fabric pests will detect the dried sweat residue and lay their eggs on it. Some fabric pests can digest cotton and linen (cellulose), but cotton knits and linen stained with additional nutrients, or starched for a crisp appearance, are more likely to be attacked than washed, non-starched cellulose-based fabrics.

What else could account for holes in fabric items if rodent and insect pests are ruled out? Based on a brief study of fabric-related issues (obtained by entering the phrase “mystery holes in fabric” in my favorite Internet search engine), the following possibilities should be considered and explored, depending on each particular situation:
■ Deleterious effects of extended exposure of synthetic weaves (comprising window draperies, tablecloths, etc.) to bright sunlight.
■ Degrading chemical reaction resulting from exposure to a strong acid, base or solvent, such as spattering with battery acid or some caustic cleaning agent.
■ Repetitive exposure effects from laundering with bleach.
■ Gradual unraveling of the fabric weave following a minute puncture or snag from
a sharp, jagged, or abrasive object, such as
a thorn, splinter, cat claw, pin or zipper.

Treatment strategies

Often, your customer will not remember any particular causative exposure or circumstance to the garment or fabric item in question. In such cases, it is advisable to monitor the vicinity of the damaged fabric item(s) by placing folded sticky pest monitors, with or without pest pheromone lures, close to the problem site — in the dresser cavity, closet, windowsill or along a nearby baseboard, for example. Ask your customer to allow the monitors to remain in place for at least one week before examining them for evidence of possible fabric pests.

As a follow-up or alternative measure, you might want to suggest to your customer that the fabric item(s) in question be cleaned and isolated in a tight plastic garment bag or snap-lid plastic bin for further observation.

If more holes appear or existing holes become larger, then a convincing argument for a non-pest source will become apparent.

The use of any pesticide treatment for mystery holes, without first confirming the presence of a fabric pest, is not advisable. Pesticide label interpretations aside, the implied message of an intended corrective or preventative treatment is that any fabric pests that might be present will be controlled. If the mystery holes continue to appear following your application, guess who will be held accountable?

It’s your decision. It’s your reputation.

Dr. Gerry Wegner, BCE, is with Varment Guard Environmental Services and ProGuard Commercial Pest Solutions.

This article is tagged with and posted in Stored Product Pests

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