Jun 8, 2011 – Munchin’ On Wool
QUESTION:
What are the main biological and behavioral
differences between the Webbing Clothes Moth
and the Case-making Clothes moth? Also, what are the most helpful preventive measures and the more appropriate treatment protocol?
ANSWER:
The Webbing clothes moth (WCM) and the Case-making clothes moth (CMCM) are very closely related. They both are in the moth family Tineidae but in separate genera – Tinea and Tineola. They are among a handful of small moths whose caterpillars are truly capable of eating and digesting the keratin in animal products such as hair, feathers, or skin. They are never really common, but when they do occur sometimes it can be in significant numbers. A couple of other moth species also occur that are very similar to the CMCM, and these are the Household Casebearer Moth (Phereoeca uterella – HCM) and the Plaster Bagworm (Phereoeca praecox – PB), although there is some disagreement on the actual names and separation of these two moth species. However, on a regular basis I see infestations of the PB in southern California, and on a few occasions have seen pretty big infestations of the HCM as well.
One piece of the biology of these moths that may not be well known is that fungus is an alternative food resource for them, and in fact the times I have seen the HCB moth the larvae were just thick on wood where the white fungal mycelia was growing in a wet area. This could be a confusion for you if you find the larvae, in their little silk cases, wandering around within a structure and assume they must be infesting some fabrics someplace. Instead, they may have wandered away from some place where molds or fungi were growing. The PB moth may feed on fabrics like the CMCM does, but it also is a general scavenger and may instead be feeding on other organic materials they find, including spider webs and dead insects. In general when you take a close look at the silk cases of these 3 similar moths you find the case of the CMCM is composed of bits of material (threads, etc.), the PB case is covered with fine grains of sand and dirt, and the case of the HCB moth often is very dark, due to the molds or mildew incorporated into the case.
The WCM larva does not make a little silk case to carry around with it as it wanders, but instead creates a “tunnel” of silk over itself on the material it is infesting. Within this silk you generally find large accumulations of fecal material, and the silk and these fecal pellets help distinguish the damage as being from the moth and not from carpet beetles. This moth is more likely to pupate right there on the material it was eating, whereas the CMCM larva is a very active larva, and often will be found wandering and dragging it silk case a great distance from whatever it was infesting. This makes it more of a challenge for you when you find the larvae to then search to discover the actual source of the infestation.
Control MUST begin with finding the source of the problem. It is tempting to “fog” a room to kill off all the moths resting on the walls and ceiling, but this really does nothing to stop the problem. The infested items are going to be hidden someplace in a closet, dresser, or storage box that a fog or mist will not touch. A careful inspection will finally reveal the source which then can be disposed of or treated in some manner to kill the larvae and eggs on it. If the damage is too great then simply placing it in a sealed bag and tossing it is recommended, but if the item can be salvaged then dry cleaning or laundering in hot water and hot dryer will work. The area should be thoroughly vacuumed, possibly treated locally with a residual insecticide, and the items then stored in a sealed container to prevent re-infestation. The use of moth balls of PDB (paradichlorobenzene) is excellent for killing moths and larvae and for repelling them from the storage location, but these also impart a strong odor to the fabrics near them, and this may not be appropriate. The moth balls also evaporate and need to be replenished constantly, so storage of susceptible items in sealed bags or boxes is preferred. Cedar-lined chests and closets really do very little to repel any insects, and of course ultrasonic repellers are useless scams.
Both of these moths as larvae will feed on feathers, wool and other animal hair products, dead insects, etc. They may attack stuffed animal mounts, and protecting these is difficult without disfiguring the look of the mount. Pheromone traps do exist to attract the adult moths as monitoring devices, and these can be placed and replenished quarterly. Pesticides play almost no role in “preventing” problems from clothes moths, and the emphasis should be on proper storage of the materials that the larvae may feed on.
Pest QuestionsJune 10, 2011
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