Overview of Damage Prevention and Control Methods
- Rotate to annual crops
- Rotate or cover crop with grasses, grains, or other fibrous-rooted plants
- Apply herbicides to control tap-rooted plants for 2 consecutive years
- Flood land
- Small wire-mesh fences may protect ornamental trees, shrubs, and flower beds
- Plastic nets to protect seedlings
- Protect plastic pipes and underground cables with metal pipes or surround them with coarse gravel
- Nothing effective
- Zinc phosphide
- Aluminum phosphide and gas cartridges
- Not practical
- Specialized body-gripping traps
- Baited box and cage traps
Damage Prevention and Control Methods
Pocket gophers can be controlled effectively whenever new mounds are being constructed. Most use of traps and toxicants should occur during spring and fall when pocket gophers are building mounds.
Botta’s pocket gophers at a density of 32 per acre decreased the forage yield by 25% on foothill rangelands in California, where the plants were nearly all annuals. Plains pocket gophers reduced forage yields in eastern Nebraska by up to 46% in dry land alfalfa and 35% in irrigated alfalfa. Losses of 30% were reported in hay meadows.
When alfalfa is rotated with grain crops, the resultant habitat will not support pocket gophers. Plants that produce grain do not establish large roots for storage, so there is insufficient food to sustain pocket gophers year-round. Plant 50-foot buffers of grain around hay fields to render the habitat unsuitable for pocket gophers and to minimize immigration by pocket gophers.
Control forbs that have large underground tap roots by chemical or mechanical means, to minimize damage by Thomomys to rangelands, orchards, and shelterbelts. This method is less effective for plains pocket gophers, as they can survive on grasses. Warm-season prairie grasses have relatively large roots, which are sufficient for sustaining Geomys.
Irrigate fields by flooding to greatly reduce the suitability of habitat for pocket gophers. Water can fill tunnels of pocket gophers, causing occupants to drown or flee to the surface, making them vulnerable to predation. Flooded soil may become sticky, which will foul the fur and claws of pocket gophers. As soil becomes saturated with water, the diffusion of gases into and out of the burrow is inhibited, creating an inhospitable environment. The effectiveness of flooding can be enhanced by removing high spots in fields that may serve as refuges during irrigation.
The use of fences around highly valued ornamental shrubs or landscape trees is expensive but may be justified. Fences should be buried at least 24 inches with an additional 6-inch skirt bent to the exterior of the exclosure. The fence must extend 1 foot aboveground to prevent pocket gophers from entering at ground level. The mesh should be small enough to exclude gophers; ¼- or ½-inch hardware cloth will suffice. Cylindrical plastic netting placed over the entire seedling, including the bare root, can significantly reduce damage to newly planted seedlings.
Utility cables and irrigation lines that are buried can be protected by enclosing them in plastic or PVC pipe if the outside diameter of the pipe exceeds 3 inches. Pocket gophers can open their mouths only wide enough to allow a 1-inch span between the upper and lower incisors, which precludes them from damaging a 3-inch diameter pipe. Soft metals, such as lead and aluminum used for armoring cables can be damaged by pocket gophers if the diameters are less than 3 inches. Underground telephone and fiber-optic cables can be protected from damage by pocket gophers by surrounding the cable with 6 to 8 inches of coarse gravel. Pocket gophers usually burrow around gravel 1 inch in diameter, whereas smaller pebbles may be pushed to the surface.
No frightening devices are known to be effective for the control of pocket gophers.
Plants such as caper spurge, gopher purge, and castor-oil plant have been promoted as repellents for pocket gophers, but evidence of their effectiveness is lacking. We do not recommend using these plants, as they may be invasive and some are poisonous to humans and pets.
High concentrations of capsaicin have been shown to reduce underground damage on structures from gnawing by pocket gophers. Unfortunately, the effectiveness in field conditions has not been demonstrated and no products are registered.
Several rodenticides currently are registered for the control of pocket gophers. Two-percent zinc phosphide is formulated as grain baits and pellets. Anticoagulants, chlorophacinone and diphacinone, are formulated as pellets and bait blocks, respectively. Toxic baits must be placed in tunnel systems by hand or a burrow builder machine. If the label has directions for use with a burrow builder machine, then it is a Restricted Use Pesticide. Burrow builders deliver bait underground mechanically, so areas greater than 2 acres can be treated economically for pocket gophers. They are tractor-drawn and hydraulically operated or mounted to a 3-point hitch.
Underground baiting for control of pocket gophers presents minimal hazards to non-target wildlife. Toxic bait that is spilled on the surface of the ground may be hazardous to ground-feeding birds such as mourning doves. The main drawback to grain baits is their high susceptibility to decomposition in damp burrows. Parafinized-baits are more resistant to the negative effects of moisture. Avoid using toxic bait when rain is in the forecast.
Baiting by hand involves opening the burrow system with a metal rod and placing bait in the burrow. Although baiting by hand is more time-consuming than probing, it leaves no doubt that the bait is delivered into the tunnel system. A hand-operated probe for dispensing bait (Figure 8) can be used to dispense bait more quickly in burrows.
To use the hand-operated dispenser, push the button when the probe is in a burrow and a metered amount of bait drops into the burrow. Efficient and effective use of bating requires knowledge of the location of the burrow system. The main burrow generally is found 12 to 18 inches away from the plug in a fan-shaped mound (Figure 9).
Dig 12 to 18 inches away from the plug. When the main burrow is located, place a rounded tablespoon of bait in each direction in the burrow. Place the bait well into each tunnel with a long-handled spoon, and then block each tunnel with clumps of sod and soil. Bait blocks also are applied in this manner. If an opening near the bait is detected by a pocket gopher, it may cover the bait with soil as it plugs the opening. Pocket gophers travel much of their burrow system during a day.
Place a probe over the tunnel where you expect to locate the main burrow and push downward. The amount of friction on the probe will decrease quickly when the point of the probe enters the tunnel. Round out the opening to the burrow with the probe. Place toxicant down the opening and cover the hole with a soil plug so the pocket gopher does not cover the bait.
Fumigants that are federally registered for use on pocket gophers include aluminum phosphide and gas cartridges with various active ingredients.
Fumigants usually are not successful in treating pocket gophers because pocket gopher tunnels are too extensive for sufficient flow of gases. In addition, pocket gophers may plug the tunnel to prevent movement of gases.
Shooting is not a practical method for controlling pocket gophers.
A variety of traps are available for trapping pocket gophers. All of the traps are effective, and the decision of which to use depends on the size of pocket gophers in your area and personal preference. For effective trapping, first find the tunnel. The procedure will vary depending on whether traps are set in the main or lateral tunnels (Figures 10a and 10b).
Locate the lateral tunnels by finding a fresh mound with moist, dark-colored soil. With a trowel or shovel, dig several inches away from the mound on the plug side. The lateral tunnel may be plugged with soil up to a few feet, but fresh mounds usually are plugged only a few inches. You may have to experiment with the types and placements of the traps. Some trappers leave tunnels completely open and use traps that work on lateral tunnels (box trap or Cinch® trap). Others close off the tunnel completely with sod or a piece of wood or plastic after they place traps in the lateral and main tunnels.
Research indicates there is no difference in efficacy between open and closed sets.
Mark the locations of traps and anchors with flagging and use wire or chain to prevent removal by predators. Never use string or rope to secure traps, as pocket gophers can gnaw through them.
Trapping is most effective in spring and fall when pocket gophers are pushing up new mounds. New mounds are darker, taller, and the soil does not clump. If a trap is not visited by a pocket gopher within 48 hours, move it to a new location. The use of traps in the winter, when feasible, will lower the spring breeding population.
Most traps used for pocket gophers are body-gripping traps, such as the DK-1, Macabee®, and Cinch® traps. Body-gripping traps typically are not baited, but some trappers place lettuce or alfalfa behind the trap to lure the pocket gopher. If safety is a concern, place a ½-inch plywood board over the hole to prevent someone from stepping in the hole or accidentally encountering the trap. Place soil around the edges to make the hole appear dark to the pocket gopher.
Pocket gophers can be caught by cylinders made of PVC pipe. The trigger end may be capped with ¼-inch hardware mesh or sheet metal. Construct the door with 50-gauge metal or a flat bar. The door should be rigid and cover the majority of the opening to prevent escapes. Trap doors may be activated by gravity or rat-sized snap traps. Cage traps can be baited or left unbaited in runways. Use traps that are at least 12 inches long. Only allow light to enter from the bait-end and cover the rest of the trap so it is dark.
Relocation of pocket gophers is suitable only in rescue situations.
Translocation of pocket gophers is not recommended.
Pocket gophers can be euthanized quickly with carbon dioxide.
Check your state regulations regarding disposal of carcasses.