During late March and April we get many calls about voles and vole damage in turfgrass. Voles are among the most important vertebrate pests in turf areas. Unfortunately the name ‘vole' is very close to the name ‘mole' causing some confusion and miscommunication. Even though both can damage turfgrass – the differences between voles and moles is vast, and it is important to understand that they are not related.
Voles are true rodents, and belong to the order Rodentia and family Arvicolidae . The word vole refers to "field"-- earlier uses of the word were used as vole-mouse, and eventually became simply voles. People often refer to voles as meadow mice, or "field mice".
Voles are of pest significance in turf and landscaped areas for two reasons; they tunnel and burrow in turf areas, and they gnaw on the trunks and roots of various trees and ornamental plants
In general, voles are compact rodents with stocky bodies, short legs, and short tails. Their eyes are small and their ears partially hidden. They usually are brown or gray, though many color variations exist. The adult vole ranges from 3.5 to 5 inches in length and weighs 1 to 2.5 ounces.
Voles are prolific. They can produce from 5 to 10 litters per year, with an average of 5 young per litter. Gestation is about 21 days, and females may mate again the day that the young are born. Young voles grow quickly, are weaned at 2 or 3 weeks, and are sexually mature in a month or two.
When conditions are favorable, voles are perhaps the most prolific of all rodents. There are cases of meadow voles producing up to 17 litters in one year for an amazing 83 offspring. Assuming that her offspring also mated and reproduced, several thousand voles could result from one female in a years time.
Fortunately, the high reproduction potential is offset by relatively high mortality rates. The vole is the most common food source for predatory birds, and is a significant component of the diet of coyotes, foxes, snakes, skunks, and other animals. Most voles do not live for more than a few months. However, if they escape all predators, a vole can potentially live up to two years.
Voles are herbivores. The stems and leaves of grasses comprise the majority of their diet, but they will also consume other green vegetation and fruits. Voles do not hibernate and are active throughout the year. During severe winters and snow cover, when green vegetation is scarce, voles often girdle tree trunks and roots killing or damaging trees and shrubs. Voles may be active day or night, but most activity occurs at dawn and dusk. Their activity is comprised of short, quick visits from the burrow through their runways and back. They typically will make 15 -20 forays from the nest, each foray lasting only about 10 minutes. Thus the vole itself is rarely seen. Most people realize they have voles only from the damage.
The meadow vole constructs well-defined, visible surface runways through turf areas, measuring about 1.5-2 in./4-5cm. in width. It is the sight of these paths that cause superintendents concern in March and April.
Vole runways in turf are formed by a combination of the vole eating the grass blades, and the constant traveling over the runway. Voles also spread excavated dirt from the burrow system in the runway, resulting in 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 some object lying on the ground. Burrows may be located beneath protective cover such as vegetation, shrubbery, beneath a rock, or beneath planter boxes. Occasionally, they are located in the open spaces in fairways or greens. In rough areas containing shade trees, burrows are commonly established beneath the tree out to the drip-line. Burrow entrances measure about 1-1.5 in. /2.5-4cm. in diameter. When workers find mysterious holes and pathways on the golf course that fit these measurements, it is usually a good indication of a vole infestation.
One of the major keys to managing voles is to realize that in many cases voles are associated with dense cover. Inspections should begin along building exteriors. First inspect the immediate landscaping outside of the building looking for runways leading from any dense areas cutting through turf. Landscape plantings with low-lying plants such as arborvitae, creeping yews, junipers, and similar species are good candidates for vole activity.
Runways that are broadest and appear especially well worn are usually high activity areas. These areas become marked by vole urine and feces accumulations. As populations build, many of the individuals within the vole colony use the same major runways. Time spent during the inspection to identify runways that lead to burrows beneath cover will pay off in proper trap or bait placement, and facilitate effective control.
The most effective methods of managing voles in turf areas is via cultural practices, the use of traps (minor infestations), and the use of rodenticides.
By eliminating weeds, and dense ground cover around lawns the capacity of these areas to support voles is reduced. Lawn and turf should be mowed regularly.
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 periods when many vole species are easiest to trap. Trapping is not effective in controlling large vole populations because time and labor costs are prohibitive.
Zinc phosphide is the most commonly used toxicant for vole control. It is a single-dose toxicant available in pelleted and grain bait formulations. Zinc phosphide baits generally are placed by hand in runways and burrow openings. Zinc phosphide baits are potentially hazardous to ground-feeding birds, especially waterfowl. Placing bait into burrow openings may reduce this hazard.The anticoagulant baits used against house mice and rats are also effective in controlling voles. Anticoagulants are slow-acting toxicants requiring from 5 to 15 days to take effect. Multiple feedings are needed for most anticoagulants to be effective. One or more anticoagulant baits are registered for controlling voles in many states, but the state regulations must be consulted prior to use.
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