Moths and their larvae coupled with dampness is the biggest enemy of wool rugs and carpets. Contrary to common belief the moth itself does not feed from wool fabrics, however, female moths do lay their eggs which hatch into harmful larvae that can cannibalize your rug. This larvae feeds off the wool over an extended period before turning into a cocoon and subsequently into an adult moth.
As with most things the best treatment is prevention rather than a cure. Rugs and carpets left in dark or damp places are most at risk, moths seek out dark undisturbed areas to lay their eggs, meaning rugs in storage or areas under furniture are prime nesting spots. It is advised to vacuum your rug regularly and ensure to vacuum the reverse and area under your rug from time to time. Rugs hung on walls should be handled regularly, the human scent can help deter moths using the rug as a nesting site. If you spot larvae or cocoons then it means there is a moth problem. If caught early this is not a huge deal but the problem can quite easily spread and become a major infestation; moth infestations can spread from carpet to rug to clothes and quickly spread around the home.
Rugs with moth infestations should be thoroughly checked: vacuum front and back and spray with wool safe specialist moth spray. As with any chemical, even those which are natural, always pre-test on a small inconspicuous area. Moth balls are not recommended as they are unlikely to work and can be harmful to humans, pets, the environment and the rug. The best option, and safest for the rug if carried our correctly, is to have the rug professionally frozen. This involves packaging, preferably in as close to a vacuum seal as possible, and freezing it for a number of weeks in order to kill any infestation, the rug is then defrosted over the course of a few days before being unpacked. This option not only kills any moths, larvae and eggs in the rug but avoids chemicals coming in to contact with often fragile fabrics.
Of course once you remove the infestation from the rug there may still be a problem with airborne adult moths in the vicinity. Moth traps using pheromones can be useful to attract the male cloths moths, giving off the scent of a female moth in order to lure the male moth into the trap. In the worst case scenario rugs can be destroyed by the moth larvae, if caught early the damage will not be noticeable however the likelihood is that the damage will be somewhere in between. Damage can be repaired but can be costly so it is always best to be vigilant and check for signs of moths from time to time.