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| Photo from http://www.agry.purdue.edu/ |
Voles are small, chunky, ground-dwelling rodents. Mature voles are 5 to 7 inches long and have stocky bodies, short legs, and short tails. Adults are chestnut-brown mixed with black, and their underparts are dark gray. The underfur is generally dense and covered with thicker, longer guard hairs. Their feet are brownish, and the thin hair that covers their tails is dark on the upper surface, gradually changing to a lighter gray beneath. They have small black eyes, and their ears are furred and do not project much above the hair. The young are uniformly gray.
Voles have other common names, including meadow mice, ground moles, field mice, and meadow moles. The use of these terms can cause confusion when identifying rodents. It is important that small mammals be identified correctly before starting control activities, since materials and methods effective against one species may not be useful on another.
Voles are frequently mistaken for moles, shrews, and mice. Moles have greatly enlarged front feet, with prominent digging claws. Moles also have no external ears and very small eyes. Shrews are smaller than voles, and have long, pointed snouts and pointed front teeth, with their eyes and ears nearly hidden in their fur. Voles have rounded, blunt snouts, and their front teeth are chisel-shaped. Their eyes and ears are readily apparent. The distinction between voles and mice is less obvious. The best way to distinguish them is by tail length. Mice have long tails that extend nearly half their body length, whereas voles have short tails.
The three vole species that cause damage Kentucky are pine voles (Microtus pinetorum), prairie voles (Microtus ochrogaster), and meadow voles (Microtus pennsylvanicus). Identification of individual species is essential because pine vole damage occurs below ground.
Voles eat a variety of grasses and broad-leaved weeds. They will also eat seeds, tubers, bulbs, and rhizomes. Prairie and meadow voles feed on tree bark primarily during the fail and winter. However, pine voles characteristically attack trees of all sizes during all seasons. Most pine vole damage occurs below ground where the animals feed on rootlets and the bark of larger roots.
Voles do not hibernate and are active all year long. They are most active during the day. Areas of activity are small (1/4 acre) and depend on population number, food supply, habitat, and season. A typical vole habitat consists of heavy, dense ground cover where the animals construct many burrows, tunnels, and runways. A single burrow system may contain several adults and young.
Voles breed from January through October in Kentucky and can produce an entirely new generation within about 60 days. Vole numbers fluctuate from year to year; under favorable conditions, populations can increase rapidly.
Although voles have a high reproductive rate, they are also a mainstay in the diet of hawks, owls, foxes, coyotes, and other meat-eating animals. In addition, the lifespan of a vole is short, ranging from 2 to 16 months. More than 80% of young voles die in their first month of life.
The best approach to managing vole damage is to use an integrated system with a variety of techniques. Not all techniques work in every situation, and orchard owners must be willing to use different approaches for their individual problem. Often a combination of techniques produces the best results. The various prevention and control techniques may be grouped as (1) biological, (2)mechanical, or (3) chemical. Each technique has advantages and disadvantages depending on management objectives, expense, location, and situation.
The three types of biological control are habitat modification, population reduction through hunting or trapping, and installation of raptor perches. Habitat modification is particularly effective in deterring voles. Dense, heavy vegetative cover, mulch, and weeds provide optimum habitat for voles by providing food and protection from predators. If you remove this food and cover source, the area will provide less suitable habitat.
Soil tillage is particularly effective because it eliminates any cover, destroys existing burrow systems, and kills a percentage of the vole population. This method of control is one of the most effective, long-term solutions in reducing vole damage. It has several advantages over other techniques because it is economical, does not place harmful chemicals into the environment, and is a long-term solution to the problem, not a quick fix.
According to Penn State Extension Research, repellents containing thiram (a fungicide) or capsaicin (the ingredient that makes chili peppers hot) are registered for vole control. Little data is available on the effectiveness of repellents to deter vole damage. Therefore, repellents should not be used as the sole method of vole control.
Thiram-based repellents are labeled for use on tree seedlings, shrubs, ornamental plantings, nursery stock, and fruit trees. Most labels only allow thiram to be used on fruit trees during the dormant season. Capsaicin-based products are labeled for use on ornamental trees, fruit and nut trees, fruit bushes and vines, nursery stock, shrubs, and lawns. Capsaicin should be applied only before the fruit sets or after the harvest. Capsaicin is registered for use on vegetable plants and agricultural crops only before edible portions and/or heads begin to form.
To prevent a feeding pattern from developing, repellents should be applied before damage becomes significant or, in the case of monitored populations, before damage occurs. They must be reapplied frequently after a rain, heavy dew, or new plant growth. Always follow label directions for the repellent being used. Never apply repellents to any portion of a plant likely to be eaten by humans or livestock unless the label permits it.
Zinc phosphide and anticoagulant baits are registered for use on voles. These toxicants are restricted-use pesticides. Any person using these pesticides must be a certified pesticide applicator or work directly under the supervision of a certified applicator.
Zinc phosphide is the toxicant most commonly used to control voles. It is a single-dose toxicant available in pellets, as a concentrate, and as a grain-bait formulation. Zinc phosphide baits generally are placed directly into runways and burrow openings at rates of 2 pounds per acre. Although prebaiting (application of similar nontreated bait prior to applying toxic bait) is usually not needed to obtain good control, it may be required in some situations, such as when a population has been baited several times and bait shyness has developed. Zinc phosphide baits are potentially hazardous to ground-feeding birds, especially waterfowl. Minimize risks to nontarget wildlife by placing bait directly in burrow openings or in runways and tunnels under cover boards.
Anticoagulant baits also are effective for controlling voles. Anticoagulants are slow-acting toxicants in pellet form that take effect in 5 to 15 days. Multiple feedings are needed for most anticoagulants to be effective. Recommended application rates for anticoagulant toxicants are 10 pounds per acre when placing pellets directly into runways. If vole problems persist, reapply the anticoagulants 30 to 60 days later.
Because of the hazard to nontarget wildlife, it is recommended that baits be placed in bait containers. Water repellent paper tubes with the bait glued to the inside surface make effective, disposable bait containers. Tube size should be about 5 inches long and 1½ inches in diameter. Bait containers protect bait from moisture and reduce the likelihood that nontarget animals and small children will consume the bait. Bait stations also can be made from discarded beverage cans. Enlarge the opening in the end of the can so that it is about 1½ inches in diameter and place a dent in the side of the can. Put the bait in the can and place the can, dented side down, in the area to be protected. Mark the bait containers with flags or stakes so they can be relocated. Another type of bait station that has been successful is made from an automobile tire split longitudinally. Tires are placed with the hollow side down, and the bait is placed in a small cup under the tire. The tire halves are then distributed throughout the area at a rate of one per tree or one every 10 yards. Discontinue use if nontarget animals are coming into contact with bait.
Woodland voles are not as active above ground, so when targeting these types of voles, place the bait directly in runways and burrow openings under infested trees at two to four locations. If runways and burrows cannot be found, roofing shingles, boards, or other objects may be placed on the ground to encourage woodland voles to build tunnels or nests under them. Bait can then be placed under these shelters once woodland voles are using them.
Timing also influences the success of control programs. Wet weather reduces the effectiveness of toxicants. Therefore, try to place the bait when the weather is likely to be fair and dry for at least three days. Baits are most effective when naturally occurring foods are limited. Late fall is an important time to place bait for voles because this practice helps reduce populations before the onset of winter, when vole damage is most severe and snow cover precludes the use of toxicants. When the vole population is high during early spring, baits should be applied before the breeding season and before the renewed growth of ground cover reduces the chance that voles will accept bait.
Toxicants are poisonous to all forms of animal life. Nontarget animals can be injured or killed by eating toxicants directly or by eating voles that are killed by toxicants. Therefore, do not place bait in piles or on bare soil. Do not use baits where there is a chance of harming humans, domestic animals, or desirable wildlife. It is unlawful to use pesticides in a manner inconsistent with their labeling.
And Dad, if all else fails you need to get a rat terrier! I didn't even realize that we had voles around our place until we got Buddy a couple of months ago. That dog is nice enough to leave dead voles in the driveway all the time so he has proven to be very effective in the fight against voles. I'll even get you one for Father's Day if the voles are that bad at your place!
Sources:
http://www2.ca.uky.edu/agc/pubs/for/for43/for43.htm
http://extension.psu.edu/natural-resources/wildlife/wildlife-nuisance-and-damage/small-mammals/wildlife-damage-control-9-voles
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