Have you ever sunk your tractor tire into a groundhog hole, or tripped over a vole tunnel? Or maybe you came across a tree in your orchard or yard that was girdled just above the soil line? Chances are this is due to one of a few gnawing rodents we have in Missouri: groundhogs, gophers, and voles. While other rodents like mice and rats can be an issue, these larger, native rodents tend to cause more damage in agriculture. Each type of rodent has a slightly different life cycle and can cause different damage specialty crop production by directly eating plant leaves, seeds, fruit, and roots, or indirectly by digging burrows that can displace soil and damage farm equipment.

Image (A) shows voles. Credit: Missouri Department of Conservation; Image (B) shows vole runway. Credit: Kate Kammler

Voles (prairie vole – Microtus ochrogaster, woodland vole – Microtus pinetorum, meadow vole – Microtus pennsylvanicus)

• Small rodents (3-5.5 inches woodland vole, 4.5-7 inches for prairie and meadow voles) with short tails and legs and stocky bodies
• Prairie voles are the most common in Missouri, while meadow voles mainly occur in the northern half of the state in upland sites near water, and woodland voles (also known as pine voles) are found in or near timbered areas.
• Life cycle: Voles prefer habitats with dense ground vegetation or leaf litter. They do not hibernate, and breeding occurs year-round, leading to large populations that peak every 3-4 years. Female prairie and meadow voles have 5-10 litters per year with 3-5 young per litter, while woodland voles have 1-6 litters per year with 2-4 young per litter. Voles live in colonies that often contain multiple generations and spend their time either mostly underground (woodland voles) or in constructed aboveground runways through vegetation that lead to underground dens prairie and meadow voles).
• Damage:
  • Woodland voles
    
    • Girdling of trees and shrubs just below the soil surface, usually in fall and winter (look for irregular gnawing marks)
  • Prairie and meadow voles
    
    • Tree or shrub girdling at ground level (differentiated from rabbit girdling, which occurs several inches above the ground level)
    • Clipped vegetation in runways

Image of gopher. Credit: Shutterstock

Gophers (plains pocket gopher – Geomys bursarius)

• Small rodent (5-14 inches long) with cheek pouches used to store and transport food and nesting materials
• Primarily in western and northern Missouri
• Life cycle: Live in solitary burrows, breeding period is January through June, with young gophers being born April to the end of June. Females can have between 1 to 5 young.
• Damage:
  • Soil disturbance in the form of mounds that are the result of tunnel digging
  • Reduced plant vigor from feeding on and harvesting roots and vegetative growth of grasses and forbs (most noticeable on rangelands)

Refer to Kansas State University info sheet MF770 for more information: Managing Pocket Gophers.

Image of gopher. Credit: Missouri Department of Conservation

Groundhogs or woodchucks (Marmota monax)

• Medium-sized rodent (16-27 inches long) with a flattened tail about ¼ the length of its body
• Common across Missouri except in the Mississippi Lowland
• Life cycle: adults hibernate in burrows in wooded or brushy areas from October to February. After emergence mating occurs and young are born in the end of March. Females can have between 2 and 9 young each year. Young groundhogs may begin digging their own temporary burrows in midsummer.
• Damage: Soil disturbance due to tunnel systems provide the greatest damage.
  • Summer tunnel systems occur along fencerows and have 2-3 entrances with a mounded “porch”. Entrance holes are 8-12 inches wide. Tunnels lead to a large chamber 3-6 feet underground that houses the nest. Excessive weight above the chamber can cause the ground to collapse.
  • May feed on vegetable and fruit crops such as peas, beans, corn, apples or pawpaws

Refer to MU Extension info sheet G9452 for more information: Managing Woodchuck Problems in Missouri, MU Extension.

Using Integrated Pest Management for rodents

Prevention

More than one type of prevention should be used because rodents can adapt to some of these methods. Avoid frightening devices intended to scare rodents with ultrasonic noise or flashes or light. Most studies have found these tools to be ineffective, as rodents can adapt to the device over time.

• Reduce available habitat by removing tall vegetation
• Increase predation by installing raptor perches to encourage birds of prey to visit your farm
• Protect trees with cylinders of hardware cloth
• Repellents:
  • Essential oils such as black pepper, bergamot, fennel, geranium, neem, and pine needle oils
  • Products with capsaicin from hot peppers (i.e. chili flakes)
  • Feces or urine from predators (predators should be species-specific, for example bobcat, Lynux rufus, urine to repel groundhogs)

Refer to MU Extension info sheet G9445 for more information: Controlling Voles in Horticulture Plantings and Orchards in Missouri, MU Extension.

Monitoring

Monitoring the rodent populations on your farm can save you time and money in the long term by helping you establish a level of rodent damage that is negligible to your operation, and alerting you if damage begins to impact your bottom line. Depending on the size of your operation and type of crop/s you are producing, some amount of rodent damage may be acceptable. Scout for vole runways and signs of rodent burrowing in spring and fall. To look for signs of woodland voles, probe the ground around affected plants for tunnels 3 inches below the soil surface, using a ½ to ¾ inch stick. The apple test can be used to monitor where vole populations may become a problem, by excavating vole tunnels or runs and placing cubes of apple as bait. Follow up with control methods near test sites where apple is removed or partially eaten (for specific instructions see MU Extension info sheet G9445). Trapping without bait can also be used for monitoring (see more on traps in the next section).

Control

Similar to prevention, cycle through different methods of control to prevent rodents from adapting to one method. Avoid fumigating burrows because this is more likely to impact non-target wildlife.

• Traps
  • Cinch Traps and Trapline products are lethal traps that work well for voles and pocket gophers. These can be inserted into excavated tunnels or on above ground runways.
  • Wire-mesh box traps should be used for groundhogs because they are strong enough to escape from leg-gripping traps.
• Rodenticides
  • Home gardens: anticoagulants like chlorophacinone formulated as paraffinized pellets (sold as Rozol Rat and Mouse Bait Pellets) can be used. These products need to be used multiple times to kill the animal/s.
  • Orchards and farms: Zinc phosphide (Prozap Agri-Brand or zinc phosphide Rodent Bait AG) can be used as a one-time rodenticide. Products with this active ingredient are restricted use pesticides and can only be purchased and used by a certified pesticide applicator. These products may impact other wildlife if not applied properly. Anticoagulant baits with chlorophacinone and diphacinone can also be used in agricultural settings to control rodents with a lower risk to non-target wildlife.
  • Alternatives to rodenticides Powdered plaster mixed with oats and sugar can be used as an alternative to rodenticides. This mixture is delivered in an inverted T bait station, first without plaster and then plaster is added to the mixture when the bait station needs to be refilled. Use 2 part oats, 2 part plaster, and 1 part sugar.
  • Rodenticide bait should be placed near the entrance of burrows and partially hidden to prevent non-target wildlife from consuming it.
    • Homemade inverted T bait stations can also be inserted into tunnels to deliver bait. Bait can be added to the base of the T (above ground), and capped to prevent water from entering.
      

      Inverted T bait station used to control voles. The inverted T is created with the following PVC pipe sections: 1 tee, 4 22.5 degree elbows, 4 2.75in pieces of piping, 1 cap, 1 2ft pipe, and held together with cement. Credit: Philippe Pessereau, Atlas Vineyard Management

• Hunting
  • Hunting during the prescribed hunting season is an acceptable mode of control for groundhogs, and damage-causing groundhogs can be hunted outside of this season.
  • Damage-causing voles may also be shot or trapped to prevent further damage.
  • Contact your local Missouri Department of Conservation staff person with questions.

Recommendations for the use of agricultural chemicals are included in this publication as a convenience to the reader. Any mention or listing of commercial products or service in this publication does not imply endorsement by MU Extension nor discrimination against similar products not mentioned. Individuals who use agricultural chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage regulations and examine current product labels before applying any chemical. For assistance, contact your local Extension office.

Sources: