Gophers, Voles and Ground Squirrels in Hay Fields: What Actually Works

By the XES Netting team — bale net-wrap manufacturer · Updated August 9, 2026 · ~13 min read

There is a particular kind of frustration in the rodent threads on the hay forums. Someone kills a hundred gophers, feels good about it, and by the next cutting the field looks exactly the same. "My fields have gotten so bad and rough," one grower wrote. "I cringe at the site [sic] of those dirt mounds."

Burrowing rodents cost hay growers in three ways at once: the forage they eat and clip, the soil they throw into your windrow, and the equipment damage and downtime the mounds cause. This guide covers how to tell the four common culprits apart, what actually works on each, the machine problems nobody puts in an owner's manual, and — most usefully — why your control program keeps failing even when your kill count is good.

Identify the animal from the mound

Almost every wasted dollar in rodent control starts with a misidentification. The four animals that show up in hay ground want different things, live at different depths, and respond to completely different tools. You can tell them apart without ever seeing the animal.

Those mound descriptions come from University of California Integrated Pest Management's Pest Notes, and they are worth committing to memory. The mole distinction matters most: moles eat insects and worms, not roots, so a mole problem in a hay field is a soil-in-the-windrow problem and a tire problem, not a yield-loss problem. Baiting moles with grain bait — the standard gopher approach — cannot work, because moles do not eat grain.

There is one more clean tell. UC IPM notes that vole girdling of plants is generally above ground while pocket gopher girdling is generally below ground. If bark and stems are chewed at or above the soil line, you have voles.

Confirming a gopher burrow before you set anything

Gopher main runways sit about 4–12 inches deep, with the nest as deep as six feet. To find the main tunnel, probe roughly 4–12 inches out from the plugged side of a fresh mound. When the probe breaks through into the burrow it drops suddenly — about two inches. That drop is the signal. A whole gopher's burrow system typically covers 200–2,000 square feet, so a handful of mounds can all belong to one animal.

What the damage actually costs you

The forage a gopher eats is the smallest part of the bill. The bigger costs are the ones that show up at harvest and in the shop.

Soil in the forage. Every mound is loose dirt sitting proud of the field surface, waiting for your cutterbar and then your rake or merger. Soil that ends up in the windrow shows up on a forage test as ash. University of Wisconsin extension guidance puts normal ash content of legume-grass forage near 9.0% of dry matter, and notes that legume-grass forages testing 10–18% ash are likely contaminated with increasing amounts of soil. The illustration they use is blunt: feeding 25 pounds of dry matter at 18% ash is roughly like feeding 2.5 pounds of soil. Ash contributes no protein and no fermentable energy, so it displaces feed value pound for pound. We have not seen a study that measures how many ash points a given mound density adds, so treat this as the mechanism rather than a number — but the mechanism is real, and it is why fields with heavy mound pressure test worse than the stand looks.

Equipment and downtime. Mounds are abrasive and they are hard. UC IPM's note on ground squirrels applies equally to all the burrowers: burrows and mounds "make it difficult to mow, and they present hazards to machinery, pedestrians, and livestock." Sickle sections, disc mower skid shoes, rake teeth and pickup tines all pay for a mounded field.

Water going where you didn't put it. Colorado State University extension notes that vole runways and tunnel systems constructed in agricultural fields can divert irrigation water. Gopher tunnels do the same thing on a larger scale, and growers on drip or flood systems report the burrows wrecking their water distribution.

"A friend of mine made it his mission to eradicate the gophers from his farm.…"

"They have some drip tape irrigation and the gophers raise holy hell with it."

— HALLSHAY · HayTalk thread 15935

Why your gopher control doesn't stick

This is the part that almost never gets explained, and it changes how you should budget your time.

A two-year study at Davis, California compared pocket gophers in irrigated alfalfa against gophers in non-irrigated fallow ground. In the irrigated alfalfa, reproduction was continuous with very little seasonal variation. In the dry fallow ground, it happened mainly in the winter and spring rainy season. Females in the irrigated fields produced roughly twice as many litters per year — 3.6 to 3.9, versus 1.7 in the non-irrigated habitat.

The authors drew the obvious conclusion for growers: that reproductive rate, combined with how young the females start breeding, means "population recovery after control measures is likely to be relatively rapid in irrigated alfalfa fields." And they added the second half of the problem — immigration into irrigated alfalfa from surrounding ground "is also likely to add to rapid recovery if gopher populations in nearby areas are not controlled as well."

So an irrigated alfalfa field is close to ideal gopher habitat, and it is also a magnet for every gopher on the fence line. Two practical consequences follow:

• Treat control as maintenance, not a project. A one-time knockdown in a field that breeds year-round and pulls in neighbors will not hold. Growers who stay ahead of it describe a routine — checking traps as part of the morning round, or running the bait machine on a set schedule — rather than a campaign.
• Work the perimeter, not just the middle. If reinvasion comes across the boundary, the boundary is where your effort earns the most. One grower's routine is a grid across the field plus two passes around the outside; that perimeter pass is doing more than it looks like it is.

UC IPM's field guidance lines up with this: after treating, watch for fresh mounds and re-treat promptly, and check the whole area again about a month later.

Trapping gophers: the reliable method

Trapping has the worst labor profile and the best certainty. You know what you killed.

"Trapping is about the only 100% effective method we have found."

"Burrow builders/baiters work as a desperation effort over winter but do almost as much damage to a stand as the gophers do."

— haystax · HayTalk thread 15935

That second sentence is a real trade-off and you should weigh it. A burrow builder cuts a slot through an established stand. In young alfalfa or a thin stand, that is not free.

Research-backed points on gopher trapping, from UC IPM:

• Trap choice matters. The Gophinator-style trap can be more effective than the older Macabee style, particularly at catching larger, mature gophers — which are exactly the ones that keep repopulating the field.
• You don't need bait behind the trap. UC Davis testing found no benefit to adding bait.
• Human scent doesn't matter. The same work found no effect from handling. Skip the gloves ritual if you want to.
• Give it 48 hours, then move. If you haven't caught a gopher within one to two days, reset in a different location. Sitting on a dead set is the most common way to waste a week.

Growers who make trapping work treat it as a route. One described checking 40 to 50 traps morning and evening and taking 6 to 10 gophers per check; another reported 150 gophers caught with 10 traps over several months. The equipment cost is trivial — box-style traps run roughly the price of a fast-food lunch each — so the real input is your time.

Burrow builders and bait machines

Over any real acreage, the tool of choice is a tractor-mounted burrow builder — sometimes called a gopher machine or gopher getter. A shank pulls a torpedo through the soil to form an artificial tunnel, and a metering unit drops treated grain into it as you go. Gophers find the new tunnel, follow it, and eat.

Extension literature barely covers these machines. The forums cover them constantly, because they are finicky in ways nobody warns you about.

The depth problem

The single most common failure is the torpedo refusing to stay in the ground. A grower who had just bought one described trying both a 50 hp and a 90 hp tractor, arms all the way down, third-link fully extended and retracted, and still only getting an inch or two of penetration.

"The tube at the bottom of the shank needs to be close the the [sic] same depth at the gopher tunnels."

"The soil needs to be soft enough to get it buried and the wheels at the rear need to be on top, being driven by contact with the ridge of dirt. The height of the wheels will dictate the depth."

— Sterling6.7 · HayTalk thread 100363

Two things in that answer are easy to miss. First, depth is set by the gauge wheels riding the ridge, not by the three-point arms — so fighting it with hydraulics is fighting the wrong control. Second, target depth is gopher-tunnel depth, roughly 4–12 inches, not "as deep as it will go."

The other half is soil moisture. Dry, hard ground defeats the machine outright — "you couldn't get a gopher machine in the ground if you tried," as one grower put it about a drought year. That is why the classic timing is late winter or early spring: UC IPM notes mound building in non-irrigated areas is most pronounced in winter or spring when soil is moist and easy to dig, which is also precisely when your machine can get in the ground. Growers running irrigation have more latitude and often bait after a set.

Some operators add ballast — railroad iron, weight boxes — to hold the shank down. If your machine will not penetrate in reasonable moisture, check the gauge wheel height before you add weight.

Tunnel angle and grid spacing

Your artificial tunnel has to stay open. If the shank runs at an angle instead of parallel to the surface, the tunnel collapses behind you and the bait is buried in a closed slot. One grower's routine: run tunnels in a grid roughly every 100 feet in both directions, plus two passes around the field perimeter, baiting once a year in late winter as gophers become active.

Manufacturer documentation is famously thin on grid spacing — growers report not finding recommended centerline widths in the manuals at all. Spacing is a judgment call based on your mound density: tighter where pressure is heavy, wider where it is light. Coverage runs on the order of a five-gallon pail of treated grain to 15 acres, depending on how close your grid lines are.

Know what is actually in the bait

Growers colloquially call treated grain "arsenic seed," but that is not what is in the jug. The two single-feeding actives used against pocket gophers are strychnine (commonly 0.5% on grain or pellets), which UC IPM describes as the most effective type of gopher bait, and zinc phosphide (commonly 2.0%). Anticoagulant baits such as chlorophacinone and diphacinone require repeated feeding and have been restricted in some states — in California they are no longer legal for residential use.

Three legal points that catch people out:

• Bait belongs in the burrow, full stop. UC IPM states that bait application for gophers is only allowed directly within burrow systems; above-ground application is both illegal and ineffective.
• Availability and licensing vary by state. Some of these products are restricted-use and some are simply hard to source. Aluminum phosphide is restricted-use and requires a state license; newer rules limit its use to burrows more than 100 feet from any building occupied by humans or domestic animals.
• Read the label for your crop. Some rodent baits carry directions that exclude crops destined for food or feed. Hay is feed. The label is the law.

Voles are a different animal entirely

Voles will humble a gopher program, because nothing you do for gophers works on them. They live in surface runways under cover, not in deep tunnels, and they arrive in waves.

Colorado State University extension describes population swings "that range from 14 to 500 voles per acre," with numbers generally peaking every three to five years. UC IPM notes vole populations cycle with sudden increases that can send numbers soaring to several thousand per acre. Females can mature in 35 to 40 days and produce five to ten litters a year, while individual voles seldom live past twelve months. You are managing a boom, not a standing population.

Damage concentrates in winter. CSU notes most damage occurs when voles move through grass runways under the protection of snow, and that the worst damage coincides with heavy-snowfall years. That is why a stand can look fine in November and be shredded at green-up — which is exactly what growers report:

"I have 20 acres of alfalfa/orchard grass that voles moved into late last fall or winter."

"The are [sic] destroying what was a great stand, harder on alfalfa than orchard grass."

— b2jrg · HayTalk thread 19216

The control that works is cover removal

Both UC IPM and CSU are unusually direct here: habitat modification is the primary tool, and it outperforms rodenticide. CSU calls eliminating weedy ground cover and tall grass "the most successful and longest lasting method" to reduce vole damage, achieved by frequent close mowing, tilling, or herbicide. UC IPM lists regular mowing, spraying, grazing or tilling of grassy areas as the primary approach.

For a hay operation that translates into specific, cheap actions:

• Mow field borders, fence lines, waterways and ditch banks close in the fall, before snow. Those strips are the reservoir the field gets colonized from.
• Don't leave the last cutting long going into winter if you have vole history — tall matted residue is the cover they need.
• Watch for the tells: 1–2 inch runways in matted grass, open holes about 1½–2 inches across, spongy soil, and hawks working the field.

On baiting, be careful. Zinc phosphide is the common vole bait, and CSU notes it is a restricted-use product and extremely toxic. Critically, CSU's guidance includes not applying it to crops destined for use as food or feed, and notes that many of these baits are labeled for orchards, groves, nurseries and non-crop areas rather than forage. Before you buy vole bait for a hay field, read the label and confirm the crop is on it.

What doesn't work (and keeps getting sold)

The forum threads are full of hopeful methods. UC IPM has tested or reviewed most of them, and is refreshingly blunt.

The owl one is worth a pause, because it is popular advice and it is well-intentioned. Barn owls do eat a lot of gophers. UC IPM's position is that installing owl boxes is unlikely to reduce gopher numbers enough to prevent damage, and describes barn owls as unreliable for gopher control. Encourage raptors because they are good neighbours and they help at the margin — just don't cancel the trapping route.

Two methods sit in between. Propane-oxygen concussion devices (the "rodent blaster" class of tool) are described by UC IPM as somewhat effective, with real cautions: property damage, injury to users and bystanders, fire risk in dry conditions, and noise. Pressurized exhaust machines such as PERC, which force engine exhaust into the burrow system, have shown removal rates in excess of 70% in some settings — but they are expensive and practical mainly at large scale.

Harvesting around the damage

Until the population is down, harvest management is damage control — and most of it is about keeping dirt out of the bale.

• Raise the cutterbar a little in mounded ground. Every inch you drop is more soil in the windrow. On a mounded field the yield you gain from cutting low can be worth less than the ash you pick up.
• Level mounds when the ground is fit, not at cutting. A drag harrow or chain harrow across the field ahead of green-up spreads mounds thin so the cutterbar rides over instead of digging in. Doing it right before cutting just moves loose dirt into the crop.
• Rake and merge gently. Aggressive raking of a mounded field is where a lot of ash gets added. A merger that picks up rather than sweeps helps.
• Expect abrasive wear. Grit in the crop is hard on pickup tines, belts, rolls and net wrap alike. Soil-laden windrows shorten the life of everything downstream of the cutterbar — one more reason mound control pays outside the yield column.
• Watch bale shape on rough ground. Mounded fields make uneven windrows, uneven windrows make barrel-shaped bales, and misshapen bales are the ones that shed wrap and slump in storage. If your ground is rough, wrap quality matters more, not less — see our guide to why net wrap breaks on bales.

Frequently asked questions

How do I tell gopher mounds from mole mounds?

Pocket gopher mounds are crescent or horseshoe shaped, with the hole off to one side and usually plugged. Mole mounds are circular with the plug in the middle and look like small volcanoes from the side. Moles also leave raised surface ridges where they tunnel. The distinction matters because moles eat insects and worms, so grain bait cannot control them.

Why do gophers come back so fast after I control them?

Irrigated alfalfa is close to ideal gopher habitat. Research at Davis, California found females in irrigated alfalfa produced about 3.6 to 3.9 litters a year versus 1.7 in non-irrigated ground, with reproduction continuing year-round. The same work found reinvasion from surrounding untreated ground adds to the rebound, so control needs to be ongoing and should include the field perimeter.

What is the most effective way to kill pocket gophers in a hay field?

For certainty, trapping — set traps in the main burrow found by probing near a fresh mound, and move the set if you have no catch in one to two days. For efficiency across acres, a tractor-mounted burrow builder placing strychnine or zinc phosphide grain bait into artificial tunnels. Most successful operations use both, on a schedule.

Why won't my gopher machine go into the ground?

Depth is controlled by the rear gauge wheels riding on the soil ridge, not by the three-point arms, so lowering the arms further will not help. Set the wheel height for a tunnel at roughly gopher depth, 4 to 12 inches. If the ground is hard and dry the machine will not penetrate at all — wait for moisture or irrigate first.

Can I use vole bait on a hay field?

Only if the label allows it. Zinc phosphide is the common vole bait and is a restricted-use product; many formulations are labeled for orchards, nurseries and non-crop areas, and guidance includes not applying to crops destined for food or feed. Hay is feed, so check the crop list on the label before buying. For voles, close mowing and removal of grassy cover is both cheaper and more effective than baiting.

The short version

Identify the animal from the mound before you buy anything — the four culprits need four different responses, and half of the money wasted on burrowing rodents is spent on the wrong species. For pocket gophers, combine trapping for certainty with a burrow builder for coverage, run the field perimeter as hard as the middle, and accept that in irrigated alfalfa this is a permanent maintenance line item rather than a one-time fix. For voles, put the money into mowing and cover removal along borders and fence lines in the fall. And whatever the species, manage the harvest so their soil doesn't end up in your bales.

Rodenticides and fumigants are regulated products and the rules differ by state. Restricted-use materials require the appropriate licence, and every product must be used only on the crops and sites named on its label. Check current registrations with your state pesticide agency or extension office before purchasing or applying.

Featured photo: Camas pocket gopher mounds by Ian Silvernail, Institute for Applied Ecology, released under CC BY-SA 3.0, via Wikimedia Commons.