People often refer to voles as meadow mice or “field mice.” In North America, there are 19 species, but the meadow vole, Microtus pennsylvanicus; the prairie vole, Microtus ochrogaster; and the pine vole, Microtus pinetorum, are of the greatest pest significance in turf and landscaped areas. Voles damage turf and gnaw on the trunks and roots of various ornamental plants.
In general, voles are compact rodents with stocky bodies, short legs, and short tails. Their eyes are small, and their ears are partially hidden. They usually are brown or gray, although many color variations exist. The adult vole ranges from 3-1/2 to 5 inches long. Mainly, they eat the stems and leaves of various grasses, but they also consume other vegetation. Voles do not hibernate and are active throughout the year, mostly at dawn and dusk. Most voles do not live for more than a few months. If they are not killed by a predator, a vole can live for up to two years.
The meadow vole constructs well-defined, visible surface runways through turf areas measuring about 1-1/2 to 2 inches wide. Vole runways in turf are formed by a combination of the vole eating the grass blades and its constant traveling over the runway. These creatures also spread excavated dirt from the burrow system in the runway, causing a dirt-bare path in some areas.
The nests of voles may be constructed on the surface, in underground burrows, or beneath the protection of an object lying on the ground. Burrows may be located beneath protective cover such as vegetation, shrubbery, beneath a rock, or beneath raised gardens and planter boxes. Residences with low-lying landscaping such as arborvitae, creeping yews, junipers, and similar species are good candidates for vole activity. Burrow entrances measure from 1 to 1-1/2 inches in diameter.
Runways that are broadest and appear especially well worn are usually high-activity areas. These areas become marked by vole urine and feces, and often accumulations of droppings will be found here. As populations rise, many of the individuals within the vole colony use the same major runways. Time spent during the inspection to identify these areas and the locations where runways lead to burrows beneath cover will pay off in proper trap or bait placement and facilitate effective control.
Voles burrow into the root system of ornamental plants, resulting in leaning young trees and dieback on shrubs and young trees. The opening of the burrow is usually near the base of the plant and is easily seen. Bark feeding at the base of trees and shrubs during the winter may also cause dieback the following summer. Close examination of affected plants shows extensive bark removal. Realize that damage is likely to be more severe during extended cold spells with deep snow cover. In some cases, management may only be needed in the form of fencing or repellents during those times.
As mentioned earlier, voles are most prolific when they have abundant amounts of vegetation and cover. If you eliminate weeds and dense ground cover around lawns, these areas will be less able to support voles. Mow lawns and other turf regularly and clear mulch 3 feet or more from the bases of trees in areas of vole activity. Keep the snow cleared away from the base of young trees.
Mouse snap traps can be used to control a small population by placing the trap perpendicular to the runway with the trigger end in the runway. A peanut butter–oatmeal mixture or apple slices make good baits. Fall and late winter are times when many vole species are easiest to trap. Trapping is not effective in controlling large vole populations because time and labor costs are prohibitive. Traps should be placed beneath colver and as near to the nest zones as possible. To avoid injury to wildlife and pets, place them beneath boxes or protect them in some other way. Placing two to three traps spaced 6 inches apart gives quicker results.
Zinc phosphide is the most commonly used toxicant for vole control. It is a single-dose toxicant available in pelleted and grain bait formulations. The anticoagulant baits used against house mice and rats are also effective in controlling voles, but multiple feedings are needed for most anticoagulants to be effective. One or more baits are registered for controlling voles in many states, but be sure that voles are listed on the rodenticide label prior to use. Baits are potentially hazardous to other mammals and ground-feeding birds, especially waterfowl. Placing bait into burrow openings reduces this hazard.
In addition to hand placement, baits also can be placed in various types of bait containers that will protect bait from moisture and reduce the likelihood of nontarget animals and children accessing it. PVC pipe or water-repellent paper tubes with a bait glued to the inside surface provide effective bait containers. Research has shown that tube sizes of about 5 inches long by 1-1/2 inches in diameter are effective and practical.
Repellents utilizing thiram (also a fungicide) or capsaicin (the “hot” in chilis) as an active ingredient are registered for meadow voles to protect the bases and trunks of trees. These products (or repellents using other ingredients and registered for other garden and turf pests such as rabbits, chipmunks, etc.) may afford very short-term protection but the use of repellents is generally not recommended due to low efficacy. Finally, no types of frightening agents are effective against voles, and no plant exists which, when planted, will repel or scare voles away from an area.