I was a textile/museum studies major in grad school, so we learned all about this...
The smell of cedar is a natural moth repellant, but it is not fool proof. If a moth larva has nothing else to eat, it will put up with the smell. Cedar (and other herbs) will also off-gas acids that can attack some yarns, though wool is least affected by acidic environments.
Keep cedar away from pets, since it is carcinogenic to them (not to people).
Moth balls are only a repellant and do not kill eggs or larvae, and the naptha they are made of is toxic.
Moth crystals (with PBD, or paradichlorabenzyne) are the only thing other than drycleaning that will kill eggs and larvae. Unfortunately, it is also toxic to people and pets.
Insect larvae that attack wool will also attack other protein-based fibers, such as silk, or feathers. The best way to keep them at bay is not to leave large piles of materials untouched for long periods of time. Inspect your collections frequently, especially in the spring, and kill any larvae you find. (The larvae will jump off objects when you shake them). Keep your storage areas clean and dust-free. Never store fibers without cleaning them first, since the larvae like cholesterol-laden wool best (perspiration is full of cholesterol).
Be sparing in your use of plastics bags, since they contain chemicals that will attack your yarns, and the plastic can trap moisture which may cause mold growth. Make yourself some cloth bags from unbleached muslin to store your yarn. They will breathe, and when they get dusty, you can wash them.
I brought home insect eggs when I worked at a museum that had a badly-stored collection that was infested. When I discovered the larvae in my own closet, I drycleaned almost all of our wool and silk clothing (drycleaning kills eggs and larvae). Anything that I could not dryclean, such as yarn, hats with feathers, etc., I put in garbage bags with moth crystals for a month, then vacuumed the items and put them back away after airing them out and cleaning the closet. I inspect everything three or four times a year, and this month, when I did my spring inspection , I only found 2 larvae, so I'm hoping that I'm almost rid of them. The key is to catch the larvae and kill them before they reproduce.
Wool moths are tiny and white. Any other kind of moth is not harming your wool. However, there are other species that attack protein fibers, such as carpet beetles and bookworms. I am still fighting a species of insect that I have not identified yet. Fortunately, they are not as destructive as wool moth larvae, and they seem to prefer dust bunnies to wool, but I did find the two this spring in our clothing, though they had not made any holes.
If I think of anything else, I will post again.