With snow on the ground and less abundant natural vegetation, voles begin feeding on the bark near the soil surface and roots of trees and shrubs. Voles, also known as meadow mice, cause serious damage to young apple trees, especially those on dwarfing rootstocks. Voles also feed on other fruit trees, blueberries, and some ornamentals, but usually do not feed on grapes, blackberries or raspberries. Although much of the feeding damage occurs during the winter months when voles girdle trunks of woody plants, it often goes unnoticed until drought stress occurs during the following growing season and the injured trees become weak or die.
Voles are not true mice, but are small gray or brown mammals that have plump bodies with short legs and tails about an inch long. Three species of voles are found in Missouri. Adult pine voles (Microtus pinetorum) are three to five inches-long and are found in fields in and around wooded areas. These voles inhabit extensive underground tunnels, spending little time aboveground. Adult meadow voles (Microtus pennsylvanicus), which tend to be larger than pine voles, are about four to seven inches-long (Figure 1). They are found in grassy or weedy areas in northern Missouri, especially where the vegetation is not mowed. Prairie voles (Microtus ochrogatser) are the most common species found in Missouri and are about the same size as meadow voles. As their common name implies, pine voles are found in sites with dense vegetation.
Voles reproduce quickly, resulting in cyclical increases in their populations. Female voles start reproducing 35 to 40 days after birth, with multiple litters every 21 days. Breeding peaks in the fall and the spring. Meadow and prairie
Although hawks, owls, foxes, and snakes feed on voles, tall vegetation beneath low tree limbs, brush piles, and leaves provide voles with protection from these predators. Vole colonies are also protected in their network of underground runways with several openings at the soil surface. Meadow and prairie vole runways often have small clippings in them.
To reduce the incidence of voles, do not use mulch around the base of fruit trees as it provides an excellent habitat. Hardware cloth (no large than 0.25 inch mesh), about eighteen inches tall, with at least three inches underground, can be placed around the base of the trunk to protect it from vole damage. Vinyl tree guards can also prevent girdling when placed on trunks in the fall, but should be removed once growth begins in the spring as they can harbor insect pests during the growing season. Keep grass and weeds short by mowing, rake leaves as they accumulate, and eliminate brush. In orchards, remove limbs immediately after pruning.
For small populations of voles, mouse snap traps baited with a slice of apple or peanut butter and oatmeal can be used. Also, stake the trap down as voles can sometimes drag them away. With some excavation, traps can be placed end-to-end or perpendicular inside runs. Repellents are also available, but often these products wash away with precipitation and do not provide long-term vole control. Rodenticides in landscapes must be used with extreme care, out of reach of children, pets, domestic animals, and non-target wildlife, or in tamper-proof bait stations. Also, bait stations should be secured to prevent spillage from these units.
For commercial orchards, rodenticides are not applied until after all fruit is harvested in the fall. Also, some products may only be purchased and applied by licensed applicators. Multiple products and control strategies are needed to reduce vole populations in commercial plantings. These recommendations can be found in the Midwest Fruit Pest Management Guide at: https://ag.purdue.edu/hla/hort/documents/id-465.pdf.
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REVISED: February 21, 2017