How to Treat Voles
I know this may sound horrible, but I think the best way to treat voles is to use regular old mouse snap traps. Place the trigger perpendicular to the runways. You can use peanut butter to bait the traps. It is always a good idea to cover the traps with a throwaway tin pan that you would use to bake a casserole with. This will help to prevent non-target animals from getting into the traps. The pans need to be deep enough so that the trap will be able to trigger inside the pan without the kill bar hitting the top of the pan. How many of these you need is going to depend on the size of your property, but the more of them you place out, the more effective it will be and the faster it will get rid of the problem.
The best time to treat is in the fall or in the winter. That is because they will have less food at that time, making it more likely that they will go for the bait in the traps.
You should always wear rubber gloves when handling the traps. These traps can be reused by releasing the animal into the trash, and then washing off the trap with a garden hose.
I don't know that you will ever get complete control of the problem, because they will continue to come over from the neighbor's yard. However, you can greatly reduce the population this way. I think it's just one of those things that you need to do on an ongoing basis.
You can also poison them by using bait stations that were designed for rats. Just place single feed bait in the stations. I will give you a link to the bait and the stations. Place them wherever you are seeing the activity.
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Rodent bait: https://www.domyown.com/contrac-allweather-blox-rodenticide-p-80.html
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Bait stations: https://www.domyown.com/protecta-rat-bait-station-p-1292.html?sub_id=199