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In the Spotlight ... Voles
In this section of the Vermont Apple Newsletter, a different pest is featured. This information is part of "Key Arthropods, Diseases, and Vertebrates affecting Apples: A Synopsis" by Jessica Reardon and Lorraine Berkett and which appeared in the Back to Basics Resource Notebook, March 22, 2000.
Offending species: The meadow vole (Microtus pennsylvanicus) (Ord) is present throughout New England. The pine vole (Microtus pinetorum) (LeConte) is present in southern New England states, and in southern Vermont, New Hampshire, and Maine.
Signs of vole activity: Meadow voles live on the orchard floor. They will chew away areas of bark and cambium that can be reached from the ground or from the top of the snow cover. They may burrow where soils are loose and crumbly, girdling the trunk below ground. Meadow voles develop a network of surface trails through the ground cover. Cuttings in ground vegetation and droppings in the trails will be noticed. Pine voles may travel above or below ground. In grass sods they live almost entirely below the surface. They will feed on the bark and cambium below the soil line, and chew off small roots in such a way that they look as though they have been sharpened by a pencil sharpener. Both species will build nests close to tree trunks, in clumps of grass, and at the end of burrows. Their nests are made of dried grasses and are circular in shape. Vole damage may occur during any time of the year, but occurs primarily in the winter. Both vole species are prolific breeders.
Identification: The best way to determine which species is present in the orchard is by trapping. Traps which are placed on the orchard floor are not likely to capture pine voles. Locate subterranean tunnels by probing the soil with your fingers. When tunnels are found place trap in the tunnel with the trip pan in the center. Use apple, rolled oats, or peanut butter as bait. The pine vole tail is short - about the same length as the hind foot (3/4 inch or less). The meadow vole's tail is longer, about twice the length of the hind foot, (1.5-1.75 inches). The body of the pine vole is smaller than the body of the meadow vole. (For more details on identification, see the 2000-2001New England Apple Pest Management Guide, Figures 40 and 41 on page 62).
Install tree guards made of hardware cloth, with the cloth embedded at least two inches into the soil (these will not prevent underground damage by pine voles, however). Remove sucker growth from the base of the tree.
In order to reduce available food sources and cover from predators, maintain a herbicide strip in the tree row. Keep the vegetation on the orchard floor mowed to below 10 inches, removing brush and weedy areas from the orchard, and removing or mowing apple drops.
Poison rotenticide baits may also be used in the orchard. Please see page 97 of the 2000-2001 New England Apple Pest Management Guide for details.
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