I had been fighting with ground squirrels for years. They dug up the pots on our patio and devastated our garden. For a few years I grew tomatoes in large pots surrounded by plastic mesh, but this barely kept the tomatoes safe from the squirrels. One year I even used a live trap to catch and relocate the squirrels, but it seemed like there was a never ending supply of the little critters.
Finally, out of frustration, I started using a device called the Rat Zapper. It was designed to cleanly electrocute rats and mice, but I found it also worked quite well on squirrels.
I've been using it for the last few years and finally this year I won the battle - no plastic mesh needed around my plants and the few squirrels that do show up are easily dealt with.
This device or one like it might help.