Site hosted by Build your free website today!


Whitney Cranshaw: Department formerly known as Entomology,
Colorado State University, Ft. Collins, CO 80523

What insects damage woolens in Colorado? Very few insects have the ability to digest wool. Among the few which do are larvae of the webbing clothes moths (Tineola bisselliella) and the carpet beetles (Dermestidae). In Colorado, carpet beetles are far more common and damaging to woolens than are clothes moths.

What does a clothes moth look like? The adult stage of the webbing clothes moth is a small moth with a wing span of about 1/2-inch. It is uniformly pale golden in color with no unusual markings other than black eyes and a coppery tuft of hairs on the top of the head. Webbing clothes moth is a weak flier and rarely leaves dark closets or other storages.

The damaging caterpillar stage is associated with woolens or fur. It is a creamy white color but often lives within a silken tube that it constructs. When full grown it may reach 1/2-inch in length.

The presence of silk and the pelleted droppings the insect produces are useful for diagnosis of clothes moths.

Are there any other insects that look similar? The Indianmeal moth (Plodia interpunctellum) is a small moth that is very common in Colorado homes. It is only slightly larger than the webbing clothes moth but is easily differentiated from it by having a general brown coloration with darker brown wing tips.

The caterpillar stage of the Indianmeal moth feeds on a wide variety of foods around the home including nuts, seeds, coarsely milled grains, prepared cereal products and herbs. However, Indianmeal moth does not feed on woolens.

What are the habits of clothes moths? The female moths lay their eggs within 1-2 weeks after they emerge. Eggs are glued to woolen threads so that they are not easily dislodged.

The caterpillar (larva) stage feeds on the wool soon after egg hatch. Often they construct a silken tube and feed in the vicinity of this shelter. Other times the larvae may continue to move across the fabric and only produce scattered small patches of silk on which it rests.

The length of time that the larva feeds varies greatly, being dependent on factors such as temperature, humidity and the quality of the woolens as food. Under ideal conditions, this stage may be completed in as little as 5 weeks; it can take up to two years.

When full-grown, the larva spins a smooth case of silk and pupates within. It emerges from this stage in about 2 1/2 weeks, becoming the adult moth. Mating and egg laying begins almost immediately after adults emerge from the pupal case. The adult moths do not feed and die within a month.

In the heat of a home, development can occur continuously producing several, overlapping generations.

Can clothes moths develop on clean wool? Development of clothes moths is slowed on clean wool and they sometimes are unable to complete their development on this material. This is because clothes moth larvae require Vitamin B as a nutrient. Perspiration, and other soiling of the fabric can provide vitamin B and clothes moth attacks are typically concentrated on soiled patches of cloth.

Although well cleaned wool is less susceptible to attack, even modest soiling can allow it to be damaged by clothes moth larvae.

How long do the eggs persist? The eggs do not remain dormant for long periods, although hatching is retarded by cool temperatures. It is a myth that eggs can remain dormant for long periods and suddenly produce new infestations when hatching months later.

How do clothes moth infestations start in a home? Webbing clothes moth is uncommon in Colorado, probably due to the arid climate that inhibits outbreaks. Most problems with clothes moths appear to originate from insects brought in on woolen or furs from more infested areas such as Mexico or the southern Pacific.

Do any other clothes moths occur in the region? Occasionally case-making clothes moths occur in the region. These include the casemaking clothes moth (Tinea pellionella) and the poultry house moth (Niditinea fuscella). The caterpillar stage of these moths produce a tightly woven silken case. Woolens and other animal products may be damaged, although feathers are the preferred food. They are very rare pests in the region.

What does a carpet beetle look like? Carpet beetle adults are small-to-medium sized (2-5 mm) beetles that are generally oval in appearance. Some species are dark gray; others are mottled with orange/brown patches amongst a lighter background color. On close inspection, the beetles can be seen to be covered with fine hairs.

Carpet beetle larvae, which do most damage, are light brown, elongate (carrot-shaped) and covered with spiny hairs. As they develop, they periodically shed their skin, which is similar in appearance to the larvae. The presence of the old 'cast skins' is useful for diagnosing carpet beetle infestations.

What do carpet beetles eat? Carpet beetles feed on an extremely wide range of foods. Dead insects, remnants of bird nests and household lint commonly support endemic populations in a home. Carpet beetles also can infest pantry items, such as prepared cereals, seeds, milk powder, and some spices.

Materials of animal origin are favored foods of carpet beetles. This includes furs, dried meat, leather, feathers, silk, hair, or wool. The name carpet beetles comes from their former importance as a pest of woolen carpets.

What are the habits of carpet beetles? Several species of carpet beetles may become established in homes including the black carpet beetle, hide beetle, furniture carpet beetle, common carpet beetle, and varied carpet beetle. However habits are generally similar.

Adult females lay eggs, often in batches, near foods that can be used by the larvae. Eggs hatch in about 2-3 weeks and the larvae feed and develop, avoiding the light. The larvae grow slowly and the length of the larval stage varies considerably in length due to temperature and the quality of food. Some species have completed a generation in as little as 3 months; others typically require a year or sometimes more to complete development. For species that occur outdoors, a one-year life cycle predominates.

When they have completed feeding, they sometimes wander away from the food source. They then pupate and may bore into wood or other objects to form a pupal chamber. The pupal stage lasts about 2 1/2 weeks, after which the adult beetles emerge.

The adult stage lasts a few months. Adult carpet beetles can fly and often can be easily observed on flowers feeding on pollen in spring.

How does wool get infested? Carpet beetle infestations within a home almost always originate from native populations of the beetles moving indoors and becoming established. Low populations of carpet beetles likely exist in the great majority of Colorado homes that are more than 5 years old.

Outbreaks tend to occur when high quality foods are left undisturbed for long periods of time. This would include wool in storage.

Are fabrics other than wool damaged by carpet beetles? Silk and wool are the only fabrics that can support carpet beetle development. Rarely, other fabrics are slightly damaged but only if they are soiled with perspiration, foods, etc. to provide nutrients required by the carpet beetles.

How do you control insects affecting wool or woolen products? The best approach to exclude the insects from woolen products that you wish to protect. Heat or cold treatment and brushing are mechanical methods to kill pests of wool. Chemical controls include 'moth balls' or 'moth crystals'.

How do you exclude insects from woolens? Most problems with clothes moths originate from infested materials brought into the area where other woolen articles are stored. Woolen material brought in from an area where clothes moths are endemic should be carefully examined and stored in a separate location (quarantined) before being placed with other woolens. Quarantining is not effective for most carpet beetles since these are common insects found throughout the region.

Tight-fitting containers are the most useful technique to prevent or limit infestations of woolen pests. Tightly closed bags, plastic containers, or containers can largely exclude insects that might damage woolens. However, since insects can develop within the containers, the stored woolens should be checked at least once a year to detect infestations.

What about temperature treatments? Freezing insect-infested wool or fabrics can kill both clothes moths and carpet beetles. Freezer temperatures less than 00F will almost always be lethal to insects following a 72 hour exposure.

To increase the effectiveness of freezer treatments, insects should be acclimated to room temperatures. The abrupt change from warm to freezing temperatures is important since insects that are slowly cooled may be more resistant to freezing. Wool or fabrics can be kept in a plastic freezer bag but attempt to remove as much air as possible before freezing.

Temperatures that are not lethal nevertheless can greatly slow insect development. Cold storage treatment used to be widely practiced for protection of furs and other valuable clothing articles that are susceptible to carpet beetles and clothes moths. Wool or fabrics can be similarly protected by storing them in cool locations within the home or even temporarily storing them in unheated outbuildings or garages.

High temperatures can also disinfest woolen materials from insects. Temperatures of 110-1200F are generally lethal to all insects if maintained for 1/2 hour or more. The practice of periodically brushing woolen fabrics outdoors and exposing them to sunlight also is effective at killing insects both by physically crushing and exposure to the sun.

Can humidity affect insect problems in wool storage? Clothes moths are very sensitive to drying conditions. Storage of woolens under arid conditions typical of the region will almost always cause infestations to die out within a few generations. Dry storage should be central to any control program for clothes moths.

Carpet beetles are well-adapted to dry conditions and are little affected by low humidity.

Have and traps been developed for control of wool pests? Sticky fly paper treated with fish meal, wool, or other attractive materials may be useful in attracting and trapping egg laying clothes moths.

There are no traps developed to control carpet beetles.

What about repellents? Two products have been most often sold as 'repellents' for insects that damage wool. Naphthalene is the active ingredient of many 'moth balls', less commonly sold as flakes. More commonly available is paradichlorobenzene (PDB), usually sold as moth crystals.

More recently an apparently effective plant-derived insecticide has been developed, lavenden. This is planned to be marketed in very late 1996 or early 1997. It will be sold for use in protecting woolens in closed closets.

What are the characteristics and limitations of paradichlorobenzene (PDB)? Paradichlorobenzene is generally more toxic to insects than is naphthalene, particularly for carpet beetles. At temperatures above about 500F it turns into a heavier-than-air gas that can kill all stages of both clothes moths and carpet beetles if maintained at high concentration for 2 to 3 weeks.

Crystal formulations release gas at a faster rate than do cakes or balls and release rate is greatly affected by temperature. PDB should be used in tight fitting containers or well sealed rooms to allow the gas to build up to toxic concentrations. Since the gas does sink, the PDB should be applied above the articles being fumigated. After fumigating, clothing or wool may be aired out, although there is no residual effect and new insects can readily reinfest the material.

Paradichlorobenzene will react with and melt some hard plastics, such as polystyrene and Styrofoam. Other plastics may also soften and melt following prolonged contact with PDB vapors-including many plastic sweater boxes. (Polyethylene storage bags are not affected by PDB vapors.) A further precaution is not to use PDB for fumigation of clothing that has plastic buttons or ornamentation.

Human health effects from prolonged exposure to PDB are not well-known, although some related compounds have associated health risks. It is therefore desirable to always use PDB in a manner that minimizes exposure.

What are the characteristics and limitations of naphthalene? Naphthalene is most often available as 'moth balls' and is a quite effective fumigant against clothes moths. Carpet beetles, however, are much more resistant to naphthalene and often are poorly controlled. Naphthalene is a fumigant, and is effective only if high concentrations of the gas are produced.

Naphthalene is best used by scattering the balls or flakes in layers throughout the fabric or wool that is being treated. However, in moist conditions, naphthalene may produce a reddish-brown discoloration due to breakdown by bacteria. Therefore it should be placed within paper or applied in some other manner so that it does not directly contact the wool or fabric.

Naphthalene does not react with plastic as does PDB. However, it may corrode some metals.

How useful are cedar chests for control of woolen pests? Not very useful.

The heartwood of red cedar (Juniperus virginiana) contains volatile oils that have been demonstrated to kill clothes moth larvae, when the oils are in high concentration. Clothes moth eggs, adults, and pupae have not been shown to be affected by these oils. The oils are not repellent to the adult stages.

Cedar chests apparently do not affect carpet beetles.

The effectiveness of cedar declines in older chests, as the concentration of the oils dissipates due to evaporation. One study suggests that chests more than three years are practically useless for killing clothes moth larvae.

On the other hand, a well-made cedar chest can exclude clothes moths. However, the newly hatched clothes moths are very small and theoretically capable of entering very small openings greater than 0.1 mm. In reality, covers that fit tightly and do not have woolen threads exposed around the opening to attract the egg laying moths are largely safe from new attacks. Infestations that have become established in a woolen storage of old cedar can continue to develop.

Whitney Cranshaw

Reprinted with permission of the author

Please note that the comments above are meant for the relatively dry and cool climate of Colorado. Adjust accordingly.
Ron Parker

Also, you might want to check out this site.

Ron .