I have grown fuchsias for many years and have been devastated when a perfectly healthy looking plant suddenly wilts and is not dry or short of water. Upon further inspection, the plant is loose in the compost and can be easily pulled up. Vine weevils have been at work eating away at the healthy roots until none are left!!! You will detect the fat white evil-looking grubs in the compost. They will have eaten all traces of root and the plant will just collapse and die. Maybe you will have seen signs of the weevil itself. It emerges at night and eats the edges of the leaves leaving circular holes.
I have found the best cure is to treat the plants before the weevils have time to lay eggs. I purchase a product called Bug Clear Ultra. I water the plants with this mixture once during the summer when the plants are fully grown and flowering. And then again and finally, when I take them inside the greenhouse before storing them for the winter.
The 2-in-1 action kills bugs rapidly and is absorbed systemically into the plant, so it kills difficult or hidden bugs as they feed, for example scale insects on ornamental plants.
I get a batch of coloured plant labels all the same colour and after watering just pop the label into the compost. Maybe pink labels for summer watering and blue labels for winter. I then know which have been treated so as to avoid missing any or watering them twice. I have tried other products and also nematodes, but find Bug Clear Ultra has worked the best for me.
Nematodes
As I mentioned earlier Nematodes are another way of getting rid of vine weevil. Nematodes are tiny worm like insects that live in soil. There are hundreds of different kinds of Nematodes, some are friendly to gardeners an others not so much. There just so happens to be a type of Nematode which kills vine weevil.
You simply mix the Nematode packet with some water in a watering can and then water onto your plants. The Nematodes do need particular soil conditions to thrive so they will do better for some gardeners than they do for others.