Huge problem here. I believe voles but may be field mice or something else. Photo of damage below- needs cut/pasting.
Over the years I have had near 100% success keeping them off the trunks by using 4-6 layers of tinfoil plus mothballs around the base.
This year around 5 trees had tinfoil chewed completely through and trees girdled, others were partially damaged but will heal.
Mulberries/apples were affected but an older plum and sour cherries also killed.
They even got a 10 year old bald cypress- chewing about 3/4" into the bark all the way around, about 4" wide swath.
The bottom 1' of most blackberries were also scraped clean of any green meaning no fruit this year. Not sure where to even start protecting those, or blueberries/gooseberries etc etc. Even raspberries are damaged.
I used hardware cloth one year but they used it as a ladder and girdled trees above the mesh.
Low hanging branches at about the snowline were also chewed this winter.
Any thoughts on other tree protection ideas? Being surrounded by farms means there are always more passing through. And I'm afraid this is between 1-2 acres so no easy feat!
Cut and pasting this should show you what they did on a sour cherry- shreds of tinfoil all over the place.