Stretch the netting over the top of the grape vines to protect the plants. The netting isn't foolproof and squirrels may crawl underneath, but it will provide some protection. Netting is also very effective for deterring birds.
Spray the leaves of the grape vine and the surrounding trellis or fence with a repellent, such as Ro-pel or capsaicin. These products have an unpleasant taste that deters squirrels. Re-apply them after rain or heavy watering.
Provide alternative food sources for the squirrel. Nail a cob of corn to a board and place it on a fence, or place feed corn, bird seed or nuts in a squirrel feeder. Squirrels must store an enormous amount of food to meet their needs. Squirrels don't hibernate, so they must have enough food stored for the winter.