We haven’t lost a tree in about 5 years since we got really serious about them. We did a subsoil experiment on a row back in 2014 which created a gopher super highway right into our orchard. It took me about 18 months of trapping to get that back under control (removed 3-5 gophers a week during this time in just 50 trees). I now know their entry points into the orchard and hammer any burrowing critter the moment we see sign. They will effect production if you don’t control them as the root systems get damaged by their activity. We also see moles and voles which we also try and control as the moles make good runways for the voles (which eat truffle) as well as openings for ground wasps (Not fun when you run over one with the mower). We haven’t had ground squirrel yet but have lost a few truffle to red squirrels scratching them. As we have native truffle in PNW we have to take a control position. We will never eliminate them so the best we can do is make it as unfriendly as possible and be diligent in our control strategy. I know some have had success by hiring a professional crew to come and set hundreds of traps just to get the population back under control. We know with out soils that we do have to do some from of aeration on a regular basis so we are currently trialing a power tiller to only shallow till. We are hoping this will give us the results we are after without giving the critters a new path in. I did at one point think of digging a fence similar to a rabbit proof one into the field (2′ deep 1/4″ S/S mesh) but abandoned the idea based on cost and no numbers to base an ROI on. Have you talked to your local university extension service about control in local conditions?