Last year I had a big problem with weevils in my salal, rhododendrons and a few other shrubs. I am not sure if they returned after putting down beneficial nematodes last fall.
Weevils are tough! You are on the right track with beneficial nematodes. It might take a few seasons to make a difference. Here is a link to information by entomologist Art Antonelli of Washington State University about controlling weevils, especially on Rhododendron.