Moths love cashmere, moths love all our favourite clothes that are made from natural fibres and in order of eating, they will start expensive.
They are a total nightmare and unfortunately I don't know of any legal substance that will eliminate them, however I am obsessed about keeping them away - far away from my home and shop.
Here are some suggestions that help me.
I store all cashmere jumpers in the summer in Really Useful Boxes, each jumper is clean and in a bag. Someone suggested recently that if you put them in airtight vacuumed bags and then store in the boxes that would work.
I frequently use Moth Bombs which I buy on line about once every two months. They are a bit of a pain as you have to turn off alarms before activating them, otherwise the smoke will set off all your alarms.
I clean my closet twice a year, taking all the clothes out and shaking them, dusting the whole area and then I spray all the corners of the room with moth spray.
I alway have hanging the sticky moth traps in the closet. They say they are not that effective, but I see the moths stuck on them, surely it helps - a few less moths in the world?
I have also in the past put my jumpers at home in bags and then frozen them for a few days - I'm not convinced its worth all that effort!
One thing for sure - if you really have a moth infestation and your closet area is carpeted, rip it out, underlay and all. Get Rent to Kill in and tell them you have cockroaches and get them to spray the floor area. Whatever kills a cockroach - is bound to kill moths!
Good luck and don't worry about the odd hole or two in your old cashmere jumper. A good quality jumper should last for years, and the odd hole or fray tells me a story that its been loved and enjoyed (not only by moths) it tells me its a quality jumper that been cherished and worn.
If anyone out there has some ideas on how to deal with this - please share with me. I am always open to suggestions. I am no expert on this subject, but I am diligent on trying to keep them away, and so far so good.