Strawberry root weevils

Transplanting our strawberries the other day, we came across some wee white grub things in the soil - a bit of Googling later revealed that they were almost certainly strawberry root weevil larvae, however information about what effects they would have or how to get rid of them, was fairly non-existent (at least, in the time I had to search).

Are these harmful, and how best to deal with them?

Also, how on earth do these things find strawberry plants? I mean, mine were in one of those re-usable growbags sat on a patio, so its not as if they were even in the soil?