Pasture Pests Pose Problems

Our farms usually fall into one of two pasture pest categories: Currently overrun, or about to be. Tunneling pasture pests can create serious hazards that can injure horses and ruin your fields. In a recent poll, 65% of the 518 who responded said they had problems with at least one type of pasture pest, from armadillos and gophers to kangaroos. We took this as a cry for help and came up with potential solutions to help rid your pastures of the most infamous of these pests.

When facing off against a pasture pest, it can feel like all-out war. As with any battle, knowing your enemy is the key to victory. Know their life cycles and styles, what they eat, and even what motivates them to do what they do to your fields. For this article, we'll look at three of the most common pasture pests in the United States: Gophers, moles, and prairie dogs.

Gophers (Geomyidae)

Gophers (also known as pocket gophers) are burrowing rodents that are strict herbivores. They eat a wide variety of vegetation such as alfalfa, clover, and other pasture grasses.

Gophers live a lonely existence. Normally there is only one gopher per complex tunneling system. A gopher's main tunnel can be as deep as 12 inches, while resting and breeding spaces can be more than 24 inches below the surface, according to Terrell Salmon, PhD, of the Wildlife, Fish, and Conservation Biology Department at the University of California, Davis.

Gophers leave half-moon-shaped mounds of excavated soil when they surface. They tend to seal off tunnel entrances with a dirt "plug," which is set just below the surface of the entrance mound. Salmon said it is estimated that a gopher can move more than one ton of soil to the surface during the course of the summer, and their burrows can cover up to 2,000 square feet.

Probing--It's important to locate the gopher's main tunnel to successfully trap him or set poison bait. To locate the main tunnel, first identify areas of recent gopher activity based on fresh mounds of dark, moist soil in the pasture. These are the openings of lateral tunnels, which lead to the surface from the main tunnels. The main tunnel can be found by probing in a circle eight to 12 inches from the mound with a metal or wooden rod--or by using a commercially available "gopher probe" (yes, they do exist). When the probe hits the gopher's tunnel, there will be a sudden drop of about two inches.

Control--For gophers, Salmon recommends trapping as an effective method of control. In order to successfully trap a gopher, he suggests digging into the tunnel with a shovel or trowel and removing any soil that might block the tunnel. Then place two traps (one in each direction) facing away from the opening. The opening in the tunnel will attract the gopher seeking to plug the hole. Trapping is most effective during the spring and fall months when gophers are more active near the surface.

The most commonly used trap is a two-pronged pincher such as the Macabee trap. Its spikes are activated when the gopher steps on a vertical flat pan in the tunnel.

Toxicants--"The key to an effective toxic bait program is bait placement," says Salmon. "Always place pocket gopher bait in the main underground tunnel, not lateral tunnels."

Locate the main tunnel and make a large opening. Place bait into the tunnel per label instructions, making sure none spills on the ground because the toxin can be harmful to other wildlife and pets. The most widely used poison is strychnine alkaloid, but it is banned in some states. Anticoagulants are also effective. Be sure to check with your county extension agent about current restrictions on use of poisons before applying any of them. Keep in mind that if you have carnivores (dogs or cats), they might eat the carcass if the gopher surfaces to die.

Natural predators--The gopher's natural predators include owls, snakes, cats, dogs, and coyotes. Farm owners might try to create a habitat to attract wildlife such as owls by providing nest boxes. However, predators rarely are able to remove all of the gophers, and trapping or baiting should be used as well.

Other methods--Flooding can sometimes force gophers from their tunnels, where they can be dispatched with a shovel or caught by a dog, Salmon says. However, gophers usually have drainage tunnels that make this difficult. Methods such as fumigation and repellents have shown very little effectiveness in controlling gopher infestation.

They're not all bad--Because gophers move such a substantial amount of dirt during the course of the year, they can actually benefit the soil by mixing and aerating the field. Weeds such as dandelions are the favorite meal of gophers, and such weeds will often replace grasses in overgrazed pastures.

Moles (Talpinae)

It's a misconception that moles are rodents, when in fact they belong to a group of mammals called insectivores (insect eaters). Moles predominantly live in areas with moist, fertile, highly organic soil, according to Gary Comer, former extension agent for The Ohio State University.

Because moles require a well-established tunnel system to survive, control becomes more difficult the longer they are allowed to tunnel, says Comer. Moles respond to changes in climate and ground moisture and will often move to another part of the property where conditions are better suited, leaving existing tunnels dormant. This is why it is important to observe mole activity before implementing a control program. Moles can dig surface tunnels at a rate of about 18 feet per hour, and they can travel through existing tunnels at a rate of 80 feet per minute.

Forget the grub--It's a common misconception that ridding the soil of grub worms will eliminate the mole's food source. No such luck.

"In fact, 80-90% of the mole's daily diet is met by the organically beneficial, gardener-approved soil maker--the earthworm," says Tom Schmidt, a professional mole trapper known as The Mole Man ( "The rest of the mole's diet can be millipedes, ants, pill bugs, and other insects found around home foundations, rocks, and landscaping timbers. In some areas of the east and the midwest, moles can feed heavily on periodic cicada (17- and 13-year locusts) for the better part of the cicada's life span. Mole populations will decrease significantly after cicadas have emerged."

He warns that time spent ridding your lawn of grubs allows moles the chance to expand their underground habitat, which can make removal much more difficult later on.

Deterrents--The use of deterrents, obnoxious substances placed in the mole runs, can temporally drive the moles elsewhere. Substances such as lye, creosote, tar, carbide, or sink flush can be placed in runways where moles enter from the property's borders. The effectiveness of such products is unknown. Poisons are largely ineffective because moles don't have the dental structure to gnaw on baits.

Schmidt says home remedies such as placing chewing gum or irritating devices at the tunnel's entrance are a waste of time. "I don't think there's a home remedy that I haven't heard about or tried," he explains. "Besides wasting valuable time, home remedies have no value in effectively controlling moles."

"Whack a mole"--Moles are sensitive to concussion. Smacking a shovel on the ground near a working mole will often stun or kill it. Comer says other active methods of mole removal include digging up or shooting a working mole. However, he cautions, unless the majority of the mole population is removed, the process will have to repeated the next year. According to Comer, some farmers have killed 100 or more moles annually, only to be faced with the same situation the following year.

Trapping--Trapping is the most effective method of mole control, and it is most successful in the spring and fall, especially after a rainfall, according to Schmidt. He suggests three types of traps that are especially effective: Harpoon, scissor-jaw, and choker loop, although he prefers the scissor-jaw such as the Out-O-Sight trap. Comer says to follow the printed instructions that come with each trap for best results. He adds that with harpoon-style traps, be sure to collapse an active run, creating a blockage, forcing the mole to reopen the tunnel.

"I tried trapping and it doesn't work!" "I hear this a lot," says Schmidt. "I usually retort that I have golf clubs, but I can't play golf. It's not the clubs, and it's not the traps. Common problems are setting good traps in bad places or bad traps in good places."

In order to effectively trap moles, it's important to understand their patterns. "To identify main runways in a yard or area, look for constantly reopened tunnels which follow more or less a straight course for some distance or that appear to connect two mounds or two feeding areas," Schmits says. "Main runways will follow fence rows, walkways, foundations, or other man-made borders." Schmidt recommends traps be set in the main runways rather than on surface feeding runways.

Prairie Dogs (Cynomys)

Prairie dogs (also called ground squirrels) are native to western North America, particularly short grass prairies. Like the other two pasture pests, they live in intricate tunnel systems with surface access through large openings or mounds. Prairie dog mounds have several functions--they prevent flooding, facilitate ventilation, and serve as lookout posts. A mound might be three to 10 feet wide and six to 12 inches high at the entrance. A density of 35 mounds per acre is common, and as many as 95 mounds have been reported.

Prairie dogs are only active during the day. They live in groupings called towns, which are usually occupied by one adult male, three adult females, and six offspring, according to Charlie Lee, a wildlife extension specialist at Kansas State University.

Prairie dog burrows also serve as homes for animals such as owls, cottontail rabbits, and rattlesnakes. As many as 89 vertebrate species have been associated with prairie dog towns.

Trapping--Lee says prairie dogs can be trapped in live trap double-door cages baited with sweet feed that are set outside the burrow mounds. However, finding a release site for the prairie dog can be difficult because it often requires a special permit. For more information on trapping and releasing prairie dogs, contact your local wildlife extension office.

Shooting--Intensive shooting of prairie dogs during their breeding season (February or March) can sometimes control population numbers.

Poison baiting--Poison grain baits are most effective during the fall when the prairie dogs' primary source of food (green grasses) has diminished. Legal poisons for prairie dogs contain 2% zinc phosphide. Label instructions should be followed for best results. (Note: To increase acceptance of poison baits, prebait with untreated oats two to three days prior.) Prebait and bait should be applied to the edge of the mound where the dirt reaches the grass.

Take-Home Message

To be fair, aside from obvious problems, these animals do have redeeming qualities. Their extensive tunnel systems allow water and air to penetrate soil, creating a more fertile and healthy pasture. Their burrows can also serve as homes for other animals.

However, sometimes the cons outweigh the pros, and a control program must be put in place. Before implementing a plan, be sure to check with your local wildlife extension service for control regulations.

About the Author

Chad Mendell

Chad Mendell is the former Managing Editor for .

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