A couple of you have mentioned that you luckily have never had any. I wish I didn't. It all started a good few years ago when one of my Rhododendrons went limp, well at first I thought it needed watering, then I tried feeding but no success. Then I was watching Alan Titmarsh (love him) on Gardeners World & he started telling us all about Vine Weevil, penny dropped & I was straight outside emptying out the pot & yes there was no roots left at all & loads of little grubs all fat. I didn't manage to save it but I did go out the very next day & bought some killer.
So for those of you who haven't seen any, I found some more :(
Now the grub on the left is a nice fat one, but on the right is a casing from one that has become an adult, so I know know they are on the loose. Not very happy.