Pocket gophers have a face only a mother could love and a reputation for causing serious production losses. The rodents really have no redeeming qualities unless they are caught in a gopher trap or taking the bait in a rodenticide probe.
Although they can be pocket-sized, pocket gophers are actually named for the fur-lined pouches on the outside of either side of their mouths that they use to carry food. The rodents can range in color from brown to black to white and measure 5 to 14 inches long. Despite being relatively small, pocket gophers can cause significant issues in alfalfa fields and irrigation systems — especially in the western U.S.
Pocket gophers readily feed on alfalfa roots as they tunnel through the soil profile, and their burrows can make it difficult to navigate hayfields during harvest, damaging equipment in the process. The prolific pests can also produce up to three litters of six offspring per year, giving them strength in numbers when it comes to digging, tunneling, and chewing through irrigation lines and utility wires.
At the 2023 Western Alfalfa & Forage Symposium in Sparks, Nev., Mark Nelson with Utah State University compared several methods and machinery for pocket gopher control. The Beaver County extension agent explained how different approaches vary in cost, efficiency, and safety while sharing some research results and anecdotes.
Rodenticide baits. Nelson said strychnine is a common type of pocket gopher bait that is exclusively used belowground. This product is lethal to pests in a single dosage and can be an effective form of control if it is strategically placed in a primary burrow.
Anticoagulant bait is less toxic than strychnine bait, which may be desirable if livestock, pets, or other wildlife are subject to consuming rodenticide. However, this means anticoagulant bait can be less effective, and two doses are typically required to kill pocket gophers. After one bad experience, Nelson said pests can develop a “bait shyness” and learn to avoid it.
“In most cases, [pocket gophers] have to eat it twice,” he said about anticoagulant bait. “If you eat something bad one day for lunch, are you going to eat it again the next day? Probably not.”
Nelson noted rodenticide bait can also be deadly to predator species — like hawks and eagles — that prey on pocket gophers that have consumed toxic products. Other methods like fumigation, combustion, and trapping are contained underground and pose less of a threat to other animals, although these forms of control still require serious precautions.
Fumigation. Aluminum phosphide and carbon monoxide are two common fumigation gases. The former comes in a tablet form and reacts with moisture in the ground to produce a toxic phosphine gas. Nelson recommended waiting until it has rained or snowed to fumigate with aluminum phosphide.
Aluminum phosphide is a restricted-use product and requires the operator to have a pesticide applicator license. The lethal gas is toxic to all mammals and can be detrimental to human safety; however, the Gopher General is a relatively new machine that is designed to mitigate these risks and eliminate contact with aluminum phosphide.
“What [the Gopher General] does is distribute aluminum phosphide tablets belowground, and the fumigant gas stays belowground. It spreads throughout the tunnels and moves throughout the soil,” Nelson explained. “The nice thing about it is you never have to touch the tablets.”
Carbon monoxide fumigation can be carried out with a pressurized exhaust rodent controller, also known as a PERC machine. It works by capturing carbon monoxide from a gas engine and driving it into a compressor where it is cooled, pressurized, and injected into a pocket gopher burrow. Nelson pointed out that soil moisture is less of a factor for carbon monoxide fumigation compared to aluminum phosphide.
Combustion. Controlling pocket gophers via combustion involves forcing propane and oxygen into burrows and igniting the gases. The explosion kills pests and collapses their tunnel systems in one fell swoop, and a contraption called the Rodenator is specifically designed for this type of combustion.
“This is one of those products that has a question mark as to how effective it is, but I will tell you one thing, it is a stress reliever,” Nelson chuckled. “But you have to be careful. Make sure you follow the label instructions.”
Trapping. Nelson stated this method is more of an art than a science as farmers must dig up pocket gopher burrows, locate the openings to underground tunnels, and set a trap in each hole. Even so, it may be safer — and more reassuring — to trap pocket gophers than to handle lethal fumigation gases or initiate a combustion reaction.
“The nice thing about trapping is you know you’ve killed that gopher,” Nelson asserted. “When you put out the bait, or you put out the gas, you hope you’ve killed it, but you can’t be sure. When you’ve actually got that gopher in your hand, then you know.”
Control according to scale
In 2023, Nelson was a part of a study that compared different control methods in fields with significant pocket gopher pressure across eight Utah counties. Each site included three plots: one to test strychnine bait, one to test Gophinator traps, and one to serve as a control.
Researchers used applicator probes to insert strychnine bait in the ground, and Gophinator traps were placed inside both tunnel holes within each pocket gopher burrow. These traps were checked three times a week for four weeks, and if a trap was sprung upon checking, it was reset.
After four weeks, data showed the trapping plots had the lowest number of new pocket gopher mounds compared to the strychnine bait plots and the control plots. With that said, Nelson pointed out that setting traps was the most time-consuming method and demanded more labor than the other treatments.
“The take home message is, if you have pocket gopher problems on small acreages or in your yard, trapping is something you should consider,” he concluded. “If you have a lot of acres to treat, you may want to look into baiting or fumigating.”
Fun for all ages
Farmers and ranchers aren’t the only ones who find satisfaction in getting revenge on a rodent that once ravaged their alfalfa fields. This became apparent through the Gopher Abatement Project, in which Nelson recruited youth in Beaver County to learn how to set pocket gopher traps and incentivized their trapping activities.
Last year, 65 children and parents attended two inaugural Gopher Abatement Project Trapping Workshops. Most participants had never set a gopher trap before, but after practicing at the training, each student left with five gopher traps a piece.
Over the next few months, kids earned $3 for every pocket gopher, ground squirrel, and rock chuck tail they returned to the country extension office. Those looking for a greater challenge acquired foot traps to catch raccoons, for which the going price was $5 per tail. The project was funded by local conservation districts, and from early March through mid-October, participants trapped more than 575 pocket gophers. Total payouts exceeded $3,700.
“The kids were happy to do it. It’s what I would call a win-win project,” Nelson said. “Not only did we trap 1,155 rodents, but we gave the kids an opportunity to do something besides play on their phones or watch TV all day.”
This article appeared in the July XL 2024 issue of Hay & Forage Grower on pages 16-17.
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