Overview of Damage Prevention
and Control Methods
- Remove or modify bird feeders to reduce spillage
- Eliminate ground cover
- Cultivate soil to destroy burrows and reduce cover
- Use wire cages to protect trees, ornamental plants, and small areas
- None effective
- Capsaicin; effectiveness is uncertain
- Fox and coyote urine, liquid or powder
- Zinc phosphide
- Anticoagulants (e.g. warfarin, chlorophacinone)
- Not practical or effective
- Mouse snap traps
- Box traps (Sherman-type)
- Multiple-catch traps
Other Control Methods
- Perches for raptors
Damage Prevention and
Often, the control of voles may not appear to be justified in comparison to the damage being incurred, but the “ounce of prevention” rule often applies. Preventive measures of control that are costly up front may prove to be the most economical options in the long-term.
Timely control of voles is important. Their populations can increase rapidly, so it is important to monitor their population levels where damage is a concern. Sliced apples placed beneath over-turned boxes provide excellent stations for monitoring of voles. Cut 1-inch, half-moon holes on the edges to allow voles to enter easily while excluding other animals. Placing apple slices under a 1-foot square of asphalt roofing shingle can work equally well. Voles do not hibernate and can be controlled whenever damage reaches levels that are intolerable.
One-hundred meadow voles per acre destroyed about 4% of an alfalfa crop, which amounts to about 1,000 pounds per acre over 7 months. Populations of 1,700 voles per acre in apple orchards in Washington decreased production by 35%, amounting to a loss of $3,036 per acre. One year after eliminating voles, the production in the orchard increased but was still below production of orchards that did not have damage by voles. Total losses for the 2-year period were estimated at $6,100 per acre. Similar loss figures for apple orchards were calculated for pine voles in New York. Voles reduced the yield of McIntosh trees by 66% and increased undersized fruit from 3% to 58%. These factors caused a $2,745 per acre reduction in income. In addition, survival of the trees through a third year was considered unlikely. One of the worst outbreaks of voles in the US occurred in Nevada in 1908 and 1909, where 10,000 acres of alfalfa were completely destroyed. In that case, the population of voles was estimated at 25,000 per acre.
Habitat modification can reduce the likelihood and severity of damage by voles. Remove or modify bird feeders to reduce spilled seed. Eliminate weeds, ground cover, and litter in and around crops, lawns, and cultivated areas to limit the attractiveness of the habitat to voles. Crushed stone placed in a yard can make that area uninviting to voles. Lawn and turf should be mowed regularly. Remove mulch 3 feet or more away from trees.
Voles can live in dense populations in ditch banks, rights-of-way, and water ways that are unmanaged. Crop fields that are adjacent to such habitat can be protected by controlling vegetation through mowing, spraying, or grazing. Soil tillage is effective in reducing damage by voles, as it removes cover, destroys existing runway-burrow systems, and kills some voles. Annual crops tend to have lower populations of voles than perennial crops because of tillage. Voles do invade annual crops when the plants provide them with cover for extended periods of time, such as minimum-tillage crop fields.
Cylinders made of hardware cloth can exclude voles from seedlings and young trees. The mesh should be ¼-inch or less in size. Bury the wire 6 inches to keep voles from burrowing under the cylinder. The cylinders should be taller than the anticipated depths of snow in winter.
No frightening devices are effective for the control of voles.
Capsaicin is registered for use on voles and is incorporated as the active ingredient in Miller’s Hot Sauce® Animal Repellent. Repellents may afford short-term protection, but have not been demonstrated in the field. Predator urine (bobcat, coyote, and fox) has been shown to be effective in reducing populations of and damage by voles. Liquid urine may not be sterilized so wear water-proof gloves during use. Do not use liquid urine on plants destined for human consumption. Use care when using as liquid urine may burn plants. A powdered formulation of fox and coyote urine is available. Thiram can be used as a bulb-dip to protect spring flowers. Check with your state pesticide regulatory agency for availability.
Zinc phosphide is the most commonly used toxicant for the control of voles. It is a single-dose toxicant available in grain bait and pelleted formulations. Zinc phosphide baits generally are broadcast or are placed by hand in runways and openings of burrows. Although prebaiting (application of similar non-treated bait prior to applying toxic bait) usually is not needed, it will increase bait acceptance, especially when a population is bait-shy. Baits made of zinc phosphide potentially are hazardous to ground-feeding birds. Placement of bait in openings of burrows or bait stations may reduce hazards to non-target species.
Anticoagulant baits also are effective for the control of voles. Anticoagulants are slow-acting toxicants that require 5 to 15 days to take effect. Multiple feedings are needed for most anticoagulants to be effective. Anticoagulant baits are registered for voles in many states. In addition to broadcast and placement by hand, anticoagulant baits can be placed in tamper-resistant bait stations, which protect bait from moisture and reduce the likelihood of non-target animals consuming bait.
It is not practical to shoot voles.
Trapping is not cost-effective for controlling voles in areas greater than 1 acre due to the time and labor costs. In small areas, trapping may be effective. Many species are more vulnerable to trapping in fall and winter when the supply of food is limited. If voles invade houses, they can be controlled by setting snap traps or box traps. Over-head cover (e.g., boards or shingles) increases success in capturing voles.
Snap traps that are intended for mice can be used to control a small population of voles.
Place the traps perpendicular to the runway with the trigger end in the runway. Baited snap traps should be covered with a box with 2, 1-inch holes cut in it to reduce the attractiveness and access of the trap to birds and squirrels. Secure the boxes to ensure free action of the snap traps. Enclosures can be made of PVC pipe and cardboard milk cartons.
Cage and Box Traps
Cage traps seldom are used, but baited Sherman-style traps are effective for capturing voles. Bait traps with peanut butter, apple slices, seeds, and cotton balls. Multiple-catch mouse traps also have been useful in catching voles, especially meadow and prairie voles. Several voles can be captured at a time, so fewer traps are needed, and non-target animals such as shrews can be released alive. Bait the traps and place them near visible burrows and adjacent to trails made by voles. If the location is correct, the trap(s) should contain a few voles in 24 hours. If you catch nothing after 2 nights of fair weather, move the traps to a new location.
Drift fences with pit traps can be used to monitor populations and can indicate when voles are immigrating to crops, orchards, or other areas that are cultivated. Pit traps may not be legal in your area. All traps should be monitored on a daily basis.
Other Control Methods
Perches or nest boxes for raptors have been installed to encourage use of an area by hawks and owls, thereby increasing predation and reducing numbers of voles. Research trials for this method have been limited and results were mixed. Although perches for raptors may be beneficial, raptors are unlikely to reduce damage by, and numbers of, voles to a level that is acceptable.