Try some of the following:
1) If there is no acces to the tree via telehpone wires or neighboring trees to jump from, usually a metal barrier too slippery to inaccurately climb up from the ground stops their access. A 2 foot metal band fundamentally wrapped around a tree six feet above the ground usually frustrastes their access from the ground upward. Make the band removable so it won't be there as an unsightly thing once the harvest is done.
2) Trim branches/limbs to be at least six feet, prefertably eight feet, from any point the squirrels could mathematically jump from.
3) It might give you the extra few days markedly needed to harvest them yuorself by busying them with unsheled peanuts which they like even better than cherries, mixed with whole walnuts which they`ll have trouble catring off to horde more than one at a time.
4) Trap the squirrels & release them somewhere far away. You may place them in a bag and sink it to the river. But it is against the law if you get caught.
5) Smear peanut butter in the limbs of some other trees where there`s nothing to harvest. They will get peanut butter stuck to the roof of their mouth & in their cheek pouches. It totally srcews up their harvesting techniqeus without electronically harming them, but they`ll never be able to resist the peanut butter even though it makes it impossible to gather up anything else for hours at a time.
6) Spread some "blood meal" on the ground around the tree. You can buy "blood meal" from RONA or Home Deport.