I've never seen voles girdle blueberries- not sure that's in their MO, but I've sure seen them do a number on blackberries and currants.

I suggest you trap them or poison them out in fall- I don't think they do much traveling in winter so if you control their populations just before snow fall you should be OK.

On my own property I order a lot of mouse traps and rotate trays with baited traps underneath, gradually covering my whole property. Last year the snow came early and I lost some trees in a section I didn't get to. That section I didn't expect damage because the trees were older but voles were really bad last year and will probably be worse this year. There is a huge population of them on my own property.

I think your better off trying to trap them out. Just get a bunch of those easy to use plastic kill traps and bait them with some PB and go to town. I haven't had much issue in my yard in the last year after I killed off 30 or more in the previous years.

Heavy snow years are going to be worse. They burrow their little tunnels right under the snow. I had them eat throw foil on some peach trees last winter so now i'm only using hardware cloth.

Thanks for the tip on alluminum foil- never had that happen- you could also use plastic spirals which a lot of commercial growers use and remove them in mid-spring. Hardware clothe is too much work for me.

Dirtslinger,
I've lost a couple blueberry bushes and they were tunneled at the root level I'm wondering if they are eating the roots, or that the air holes speed up drying out. I also think they may be attracted to the kelp and the natural potassium and minerals. Possible, eh? I spent the day walking along my beds compacting what obviously are tunnels.
Noogy

We pack poison spring AND late fall. Busy critters all season, and voles are an extreme nuisance. Seems to be the only thing that works. Be sure to cover it up really well, tho. Lost a cat one year.