get you a dog.
get you some raptors (hawks).
cut down the trees.

Seriously, this is an active time for squirrels. There is a chill in the air and so they start to stash stuff for Winter.
My neighbor (older lady) used to feed the squirrels peanuts and her back yard was full of old decrepit trees badly in need of maintenance. Attractive factors for squirrel visitors. She went away, a new guy bought her property, tore down her house, cut down the crummy trees, built himself a new house, and my squirrel problems vanished.
Squirrels used to steal all our figs, some tomatoes and they still steal most of our apples when the apples are still green. But I have been eating delicious figs for a month and my tomatoes are not touched. Probably a combination of the above factors have reduced the squirrel population and their depredations around my house. I love it. If you have a bad problem I sympathize. I'm not sure there is a cure such as tonics or cayenne pepper or spraying stuff. A dog helps some.

I haven't had to protect an entire backyard from squirrels. We have three regular squirrel visitors which I love. (They do disturb the soil in my potted plants trying to bury nuts, but I just try to live with it).
When they began eating the flowerstalks on my newly planted Heucheras (coral bells), I sprinkled red pepper in a solid ring on the ground around each plant. It worked pretty well. I had to reapply after watering. After about a month I stopped applying the red pepper (got lazy) but the squirrels did not resume eating the flowerstalks, so it turned out okay.

I am guilty of providing peanuts to squirrels (well, it is actually my elderly mother who does). But since every neighbor around me has basically turned their backyards into hardscape when they 'improved' their homes, the squirrels do not have as many places to hang out as they used to. Their population has declined too, of course.

And my 11-year-old dog is finally old and wise enough to be able to ignore the squirrels (most of the time).

Not sure why your squirrels are digging up grass?

Boy do I wish their population would decline. They dig everywhere here (Sunnyvale). We have so many that there is at least one a week dead in the street (hit by a car). The only way to keep them out of freshly planted areas is chicken wire laid flat over your planting area. They plant those peanuts anywhere they can, destroying much of my groundcover, and uprooting potted plants. I wish there was a law against putting out peanuts for wildlife. The Jays try to break them open pounding on our roof every morning. Grrrrrrrrrrrrrrrrrrrrr.

Pellet gun. BB gun too small, 22 too big.
Okay, not really, but the squirrels here are non-native invaders, and they eat avocados, oranges, bell peppers, iris bulbs, true bulbs, succulents, tomatoes, carrots and radishes, walnuts, sunflowers, cosmos, canna lilies... is there anything they don't eat??? I don't mind sharing, but THEY EAT IT ALL!!! And they scold me on top of it!!!
Someone with tech savvy needs to invent a motion-detecting zapper kind of like an electric dog collar (I know, it would be really hard to get the collars around all of their little necks, and if you had the ability to get something around their little necks in the first place you wouldn't need a zapper).
Renee

We have ground squirls up here. They are really a big problem because they dig holes in the cow and horse pastures and we have had animals that broke their leg because they steped into a hole. My neighbor sits out in his yard with a 22. He has 6 horses, I guess I would do the same thing if I had horses. They are cute little guys, but they run into the street just as we drive down it. I have hit some because they run right in front of us. That ruins my whole day.
Donna