Moths are the critical pest for piano felts. Here too, unplayed pianos are more at risk. Moths are often brought in with old carpets or clothes. Or even with the piano. The easiest way to find traces of moths (pupation remains) is to look for them on the hammers of the mechanism. If there are moth tracks in one place, they were certainly in other places on the piano.
It is not uncommon for old pianos to contain moth bags or lavender bags. These lose their effect after some time and should be replaced regularly by lavender or similar commercially available preventative agents.
A piano infested by moths can only be repaired by the piano maker at great expense. As a rule, all felts must be replaced.
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