Vole
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Scientific name
Microtus pennsylvanicus
Identification
- Body 90-130mm long
- Dark chestnut brown with greyish belly
- Ears smaller and tail shorter (35-65mm) than that of mice
Injury
- Occurs near the ground under grass or snow
- Remove strips of bark from around trees usually within 30 cm of ground
- Begin at one spot and eventually girdle trunk
- May result in tree stress or death
Biology
Meadow voles usually feed on grass seeds, herbs and bulbs during the spring and summer then shift to bark in the fall and winter. They make shallow runways along the soil surface whereas the pine vole burrows deep and feeds underground mainly on rootlets and the bark stripped from larger roots.
Vole populations rise and fall in three or four-year-cycles. At the low end of the cycle, there can be less than 100 animals in each hectare of old field habitat and less than 380 in marsh habitat. At the high end of the cycle, populations can climb to 1000 voles per ha.
Usually, the main stem and lower branches of young trees are attacked. Root damage is less extensive. Vole damage begins in August and continues through fall and winter, presumably when alternate food sources are scarce or less nutritious. Many areas of Ontario experience deep winter snow cover that offers ideal habitat for the voles. Girdling then occurs below the snow crust, making detection of damage and application of effective control more difficult.
Management Notes
Remove fallen fruit to reduce orchard attractiveness to voles.
A wide herbicide strip beneath the trees coupled with regular close mowing of row middles helps to discourage rodents. The abundance of nesting material and places to hide offered by brush and trash should be avoided. Remove straw, trash, sod, etc. from around the base of the tree for at least 60 cm from the trunk. Fall hilling with soil may also help.
For maximum protection in areas where vole injury is a problem, all newly planted trees should have a wire or plastic guard with small aeration holes placed around the trunk. The bottom of the guard should be buried in the soil 5 cm deep, or better yet, in a mound of fine crushed stone or sharp cinders. All tree guards should be checked each fall to see that they are rodent tight, free of trash, and are not interfering with root development.
A number of commercial tree guards are available. Two of the most common are spiral plastic and galvanized wire mesh. Orchard grower experience has shown that a guard approximately 45 cm high is adequate. This may be a challenge where multiple trunks are present.
If you are making your own guards, do not use dark coloured materials or tar paper. These materials can increase the temperature of the bark on sunny days in winter and subsequent low temperatures at night can cause injury to the bark tissue. Also, they provide a place for trunk damaging insects to live. Heavy aluminum foil or thin metal sheets should also be avoided. Unventilated guards of this type have the potential to damage vines by allowing the trunk to heat.
At harvest, check for signs of mice in the orchard — tunnels, droppings, fresh grass clippings in runways, and chewed apples.
Baits are most effective if dropped fruit are picked up and removed from the orchard. Before the grass falls over and the ground is covered with snow, broadcast bait over the floor of the orchard.
- Baits are best applied on bright days with no rain expected for several days.
- Several commercial formulations of bait are available for orchard use. Consult the label before application and obey all safety instructions.
- Bait stations provide a means of achieving a longer period of mice control than the broadcast treatment.
- Various materials, such as slabs of wood, pieces of board, or tin cans with one end removed can be used for bait stations. The bait is placed under the board or in the can, with the can lying on its side.
- The "inverted T" bait station made of 1½ inch ABS pipe is perhaps the most effective type of bait station available. In this station, several tablespoons of bait are placed in the neck which is capped, thus, protecting the bait from the elements.
- Bait stations should be used at a rate of approximately 25 per hectare.
- These baits are poisonous to humans, domestic animals and wildlife.
- Store the bait in a shed away from children, irresponsible persons and animals.
- Wear rubber or neoprene gloves for hazardous compounds and wash after handling poison baits.
- Avoid inhalation of dust or fumes.
- Destroy empty containers by burning or by burying in non-cropland away from water.
- Keep children, pets, and domestic animals away from treated areas.
- Where possible, remove mouse bodies and bury or dispose of them in a safe manner.
Predation by cats, foxes, weasels, coyotes, snakes and birds of prey (especially hawks, kestrels and owls) all contribute to a low mouse population. Predation may not manage high vole populations, but helps manage populations in normal years to prevent some damage.
Some information included above excerpted from;
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