Even if the bags are sealed...?
I suppose since the larvae can chomp through wool, they probably
can chomp through plastic if they have to!
I don't fancy defrosting my base layer before rides, so maybe I will just stick to artificial fibres.
The problem is multi-factorial but in short, moth larvae and their mother can certainly penetrate thinner plastics. The heavy-duty bags used in vacuum storage are good, as long as the seal is intact - and as long as there were no viable eggs on the woo. when you put it away. Plastic tubs and boxes are not mothproof, as they are not fully airtight. Moths can insert their oviposter through thin fabrics in order to lay eggs on the wool you thought you'd safely stored ...
Something that you're washing and wearing regularly is unlikely to get infested - but the minute you 'put it away for the summer' it's at risk. The central heating of houses (and hence our storage spaces) exacerbates the problem, as many more generations can develop without a chilly winter in unheated bedrooms to kill them off, or at least slow them down. The larvae prefer wool, but will also happily live in blends and even synthetics, especially if they're put away not spotlessly clean ...
Fresh air, sunshine and disturbance deters them. If moths are in your carpet, moving your furniture around frequently puts them off, at least a bit.
Heat kills the eggs and larvae, as does prolonged freezing, submersion in soapy water (24 hours, I believe), dry-cleaning chemicals, and steam-cleaning. The males are the ones you see flying around; they're seeking the female who has attracted them with perfume. She's sitting, unseen, at the back of the wardrobe near your favourite cashmere cardi or that hand-knitted Aran jumper it took you literally
months to make ...