Tuesday, July 21, 2009

Go, Go, Gophers!

     What can be found in every county in California and at any altitude from below sea level to the alpine zones?  Is it: a) smog; b) computer-controlled recorded phone calls from politicians; or, c) gophers? The answer, of course, is d), all of the above. But for the purposes of this discussion we'll limit this space to a subject where victory is possible, gopher control. 
    Botta's pocket gopher is the Central Valley's resident gopher, and has large incisor teeth projecting outside the mouth. It has a blunt head, long sharp claws, a tail with sparse hairs and relatively small eyes and ears, perfect for doing a lot of underground burrowing.

    While you're reading this, pocket gophers may be scurrying under your backyard, eating plant roots and stems while girdling or clipping tree roots. Their crescent-shaped mounds, usually found in clusters, create unsightly areas on lawns while their burrows can carry off irrigation water or dry out plant roots. (Mole mounds, by comparison, have dirt piled all around the entrance, looking sort of like a volcano). Gopher burrows are usually two to three inches in diameter and four to twelve inches below the surface, extending for hundreds of yards. (Mole burrows used for feeding are closer to the surface, usually forming a ridge on top of the soil).
   Because of their length and intricacy, flooding gopher burrows with a hose to flush out these little munchers is usually futile (unless a hunting dog or cat is waiting at a nearby burrow entrance). 

     What then, is a gardener to do? Local nurseries sell poison baits and gopher traps. Both have to be used with extreme caution because of their inherent hazards to domestic animals and small children. And to be effective, both have to be applied properly (and usually reapplied) in order to snare these small, clever creatures that are quite adept at sniffing out potential trouble (There's more below on these methods of gopher control).

     To keep gophers out of garden areas, raised flower and vegetable beds with an impenetrable screen at their base provide one solution. Build raised beds at least 15 inches high, installing sheets of hardware cloth (quarter-inch mesh wire) along the bottoms of the beds. The wire allows air and water to penetrate but keeps the gophers from munching on your summertime flowers and vegetables.
    Another effective gopher control can be cats. Some felines are natural gopher hunters, and can rid the backyard of the producers of those tell-tale mounds and will proudly show you their catches. The key, as any cat owner can tell you, is to have a strong stomach during the "presentation of the trophies". 

     In my experience, horses can provide another deterrence to gophers. The sound of galloping hooves over their heads can persuade gophers to take up residence in a quieter neighborhood. I know this because all my neighbors have horses, and we don't. We got the gophers instead.

The folks at the UC Integrated Pest Management program offer these tips for gopher control:

Trapping is a safe and effective method to control pocket gophers. Several types and brands of gopher traps are available. The most commonly used is a two-pronged pincher trap, such as the Macabee trap, which is triggered when the gopher pushes against a flat vertical pan. Another popular trap is the choker-style box trap.

To set traps, locate the main tunnel with a probe, as previously described. Use a shovel or garden trowel to open the tunnel wide enough to set traps in pairs facing opposite directions. By placing traps with their openings facing opposite directions, a gopher coming from either end of the burrow can be intercepted. The box trap is easier to use if you've never set gopher traps before, but setting it requires more excavation than if you are using the Macabee trap, an important consideration in lawns and some gardens. Box traps are especially useful when the diameter of the gopher's main burrow is small (less than 3 inches) because to use the Macabee-type wire traps, small burrows must be enlarged to accommodate them.

It is not necessary to bait a gopher trap, although some claim baiting gives better results. Lettuce, carrots, apples, or alfalfa greens can be used as bait. Place the bait at the back of a box trap behind the wire trigger or behind the flat pan of a Macabee-type trap. Wire your traps to stakes so they can be easily retrieved from the burrow. After setting the traps, exclude light from the burrow by covering the opening with dirt clods, sod, cardboard, or some other material. Fine soil can be sifted around the edges to ensure a light-tight seal. If too much light enters, the gopher may plug the burrow with soil, filling the traps and making them ineffective. Check traps often and reset them when necessary. If a gopher is not caught within 3 days, reset the traps in a different location.

Baiting with Toxic Baits
The key to an effective toxic baiting program is bait placement. Always place pocket gopher bait in the main underground tunnel, not the lateral tunnels. After locating the main gopher burrow with a probe, enlarge the opening by rotating the probe or inserting a larger rod or stick. Following label directions, place the bait carefully in the opening using a spoon or other suitable implement that is used only for that purpose, taking care not to spill any on the ground surface. A funnel is useful for preventing spillage.

Strychnine-treated grain bait is the most common type used for pocket gopher control. This bait generally contains 0.5% strychnine and is lethal with a single feeding. Baits containing anticoagulants are also available. When using anticoagulant baits, a large amount of bait (about 10 times the amount needed when using strychnine baits) is required so that it is available for multiple feedings. Although generally less effective than strychnine baits, anticoagulant baits are preferred for use in areas where children and pets may be present. When using either type of bait, be sure to follow all label directions and precautions.

After placing the bait in the main burrow, close the probe hole with sod, rocks, or some other material to exclude light and prevent dirt from falling on the bait. Several bait placements within a burrow system will increase success. Tamp down existing mounds so you can distinguish new activity. If new mounds appear for more than 2 days after strychnine baiting or 7 to 10 days after anticoagulant baits have been used, you will need to rebait or try trapping.

If a large area is infested with gophers, a hand-held bait applicator will speed treatment. Bait applicators are a combination probe and bait reservoir. Once a burrow is located using the probe, a trigger releases a measured amount of bait into the tunnel. Generally, strychnine bait is used with such a bait applicator because the applicator dispenses only a small quantity of bait at a time.

Underground fencing might be justified for valuable ornamental shrubs or landscape trees. To protect existing plantings, bury hardware cloth or 3/4-inch mesh poultry wire 2 feet deep and extended at least 1 foot aboveground to deter gophers moving overland. This method is less than perfect, however, because gophers may burrow below the wire; also, the wire may restrict and damage root growth of trees. Small areas such as flower beds may be protected by complete underground screening of sides and bottoms. When constructing raised vegetable or flower beds, underlay the soil with wire to exclude gophers. Wire baskets to protect individual plants can be made at home or are commercially available and should be installed at the time of planting. If you use wire, use light-gauge wire for shrubs and trees that will need protection only while young. Leave enough room to allow for the roots to grow. Galvanized wire provides the longest lasting protection.

Six to 8 inches of coarse gravel 1 inch or more in diameter around underground sprinkler lines or utility cables may deter gophers.

Natural Controls
Because no population will increase indefinitely, one alternative to a gopher problem is to do nothing, letting the population limit itself. Experience has shown, however, that by the time gopher populations level off naturally, much damage has already been done around homes and gardens.

Predators, including owls, snakes, cats, dogs, and coyotes, eat pocket gophers. Predators rarely, however, remove every prey animal, but instead move on to hunt at more profitable locations. In addition, gophers have defenses against predators. For example, they can escape snakes in their burrows by rapidly pushing up an earthen plug to block the snake's advance.

The idea of attracting barn owls to an area for gopher control by installing nest boxes has been explored. Although barn owls prey on gophers, their habit of hunting over large areas, often far from their nest boxes, and their tendency to hunt areas with abundant prey, make them unreliable for gopher control. When a single gopher, which is capable of causing damage rapidly, invades a yard or garden, a gardener cannot afford to wait for an owl to arrive. Effective action, usually trapping or baiting, must be taken immediately.

Habitat Modification
Reduction of gopher food sources using either chemical or mechanical methods may decrease immigration of gophers. If feasible, remove weedy areas adjacent to yards and gardens to create a buffer strip of unsuitable habitat.

Other Control Methods
Pocket gophers can easily withstand normal garden or home landscape irrigation, but flooding can sometimes be used to force them from their burrows where they can be dispatched with a shovel or caught by a dog. Fumigation with smoke or gas cartridges is usually not effective because gophers quickly seal off their burrow when they detect smoke or gas. But if you are persistent with and use repeated treatments, some success may be achieved.

No repellents currently available will successfully protect gardens or other plantings from pocket gophers. Plants such as gopher purge (Euphorbia lathyrus), castor bean (Ricinus communis), and garlic have been suggested as repellents but these claims have not been substantiated by research. Although there are many frightening devices commercially available to use on pocket gophers (vibrating stakes, ultrasonic devices, wind-powered pinwheels, etc.), pocket gophers do not frighten easily, probably because of their repeated exposure to noise and vibrations from sprinklers, lawnmowers, vehicles, and people moving about. Consequently, frightening devices have not proven to be effective. Another ineffective control method is placing chewing gum or laxatives in burrows in hopes of killing gophers

Once pocket gophers have been controlled, monitor the area on a regular basis for reinfestation of the land. Level all existing mounds after the control program and clean away weeds and garden debris so fresh mounds can be seen easily. It is important to check regularly for reinfestation because pocket gophers may move in from other areas and damage can reoccur within a short time. If your property borders wildlands, vacant lots, or other areas that serve as a source of gophers, you can expect gophers to reinvade regularly. Be prepared to take immediate control action when they do; it is easier, cheaper, and less time-consuming to control one or two gophers than to wait until the population builds up to the point where the gophers are causing excessive damage."


Joe Connell, UC Farm Advisor in Butte County, offers this advice ("Gopher Control….Better Late Than Never!") in the Fruit and Nut Notes July 5, 2009 newsletter about gophers and fruit trees:

"If you have an orchard where individual trees are yellowing, have thin canopies with small leaves, or lack of new growth, gopher damage is a possible cause. On some rootstocks, root rot or oak root fungus could also be possibilities and this should be checked out. If it’s gophers, they can be the cause of significant ongoing tree losses. 

Gophers chew off roots and can chew off bark all the way around the trunk at the crown right down to the wood. If you dig around a sick tree and find the bark missing two or three inches below ground level, you can bet that a gopher is the culprit most of the time. 

If the orchard is weedy around the tree trunks, providing cover and protection, meadow voles can chew off bark at ground level girdling trees and causing a similar decline.

Gophers are active all year and this (summer) is still a good time to reduce their population. It’s easy to see new signs of their activity when weeds are being controlled for harvest and new fresh mounds are evident. 

Be persistent. Gophers eat year around. If you do a good job of weed control in your orchard and you have active gopher mounds you can be certain the gopher will be feeding on your trees as harvest approaches. 

Gophers can damage any age tree. The easiest trees for a gopher to kill are first through fourth leaf trees (1-4 yrs. old) because they can girdle them quickly. I’ve also seen 10 year old trees killed by gophers.

The longer gophers work on trees, the weaker the trees become. Oftentimes the damage doesn’t become apparent until the year after the injury has occurred since it may take awhile for the root system to starve and decline, especially on older trees. Remember, leaves manufacture sugars that are translocated down through the phloem to feed the root system. When gophers chew off the bark the phloem pipeline to the roots is missing and the root system gradually starves. If the gopher doesn’t kill the tree and it’s only partially girdled, it can be permanently weakened with the damaged roots or crown becoming avenues of entry for crown gall and wood rots. Wood rots weaken the structural strength of roots and the crown and contribute to tree losses in windstorms.
Gophers are a serious problem but they can be stopped."
Like this.


  1. Thanks for not whispering about gophers. Although the chalk outline is kinda scary.

  2. Is it okay to put poison bait in the veggie garden? I've HAD it! My dreams are even infested by gophers.

  3. If you follow the instructions offered by UC in this article, toxic baits can be effective. For those who don't want to use toxic baits, the best alternative may be to build raised beds for your garden, lining the bottom and sides with hardware cloth.