root vole blues

So, I just returned from our orchard of approximately 150 trees. We have now lost a total of 30 trees this year. The tree roots have been gnawed down to next to nothing and pull straight out of the ground.
Current prevention strategies: We have guards around the trunk and have pea gravel in about a 3ft circle surrounding the tree. We have also started trapping and have an owl box out but is yet to be inhabited.
The understory I have tried to mow only twice per year but wondering if I need to keep it much lower cut for some time?
I need help in a desperate way!
As I replant has anyone used mesh baskets around the roots?
Are there any safe ways to bait the rodents that won't negatively impact the bird population?

All your advice and nuclear options would be much appreciated. This loss has bummed me out in a major way.
Thanks,
adam



Edited 2 time(s). Last edit at 03/24/2018 04:13PM by Michael Phillips.

Here in the East the culprit would be the pine vole, those that tunnel deeper than the surface-directed meadow vole. I saw directly on one consultation visit in coastal Massachusetts just how heartbreaking this sort of tree loss can be. The slightest tug would pull up a young tree . . . and then there was just a carrot shaped root remaining. All the cambium was gone; all root branching was gone. That particular grower went ballistic with mechanical trapping, placing a couple dozen in runs and wherever. The dynamic is better a year later, and in fact on my most recent visit to that orchard, we watched a hawk dive bomb to the ground and snag a vole.

I know you are in Spokane, Washington, Adam, verging on gopher country and probably with a different set of voles. Hopefully, those dealing with "downunder rodents" will offer yet more tips. Land mines definitely sound appropriate to me.

Lost Nation Orchard
Zone 4b in New Hampshire

we used to gas gophers when I was a kid. would dig out a hill so we could see the attached runs, place a large pie pan on the bottom of the hole, pour in bleach and ammonia, place a piece of plywood over the hole and bank the edges with the dirt we had removed. it would take out the whole colony.

Tom Kleffman
currently building a fruit orchard from scratch on the Bayfield Peninsula of Wisconsin, 4 miles south of Lake Superior, dead center of the snow belt, zone 5.