I always think of my checking account first. It is amazing what you can put up with for the right money. Client tells me to jump my answer is how high.
I have tried all of the above items... what works is rolled barley covered with warfarin and then spread very thinly over a few square yards every other day . Squirrels eat the grain when only a few are available at a time, instead of stuffing their cheeks and storing them in their hiding places. By spreading the poison grain every other day , they slowly start to bleed out in their intestines and die shortly thereafter. Purchased from the County Ag. Dept.
Rabbits go through chain link down at the other place. I use chicken wire to stop them, it doesn't stop the squirrels. I have to use the electric fence, sometimes warfarin sodium.
Distract the squirrel with a constant supply of ears of corn, preferably far away from your tree. When he is fat for winter, have squirrel gravy. Keeping the tree sprayed down with deer repellant after each rain once fruit sets should help too.
Nyboy, No, I say they go through Chain Link fencing. I put up 2' of chicken inside the Chain Link to stop the rabbits but the squirrels climb over that, so I put a hot wire there, but they, some, always find a way in.