We have been pestered in the past by squirrels eating the buds on the camellia bushes.
Stringing twine and thread does not deter them.
If you smear some good strong mustard on the lower branches or the branches that afford them easy access, you might find they leave the bushes alone.
We've had good success with good strong English mustard, some old curry paste and even horseradish sauce.
If the squirrels get the paste on their fur and attempt to clean themselves, the effect can be both amusing and rewarding in that they might leave the bushes alone.
I'm sure it will work on other plants/bushes, it just seems that our local squirrel troupe liked our camellias.