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Controlling Voles & Field Mice

Q. My garden is located in the middle of an apple orchard, which also seems to be home to mice and voles. Last year we had a huge tomato crop from 300 plants in Mittleider beds , but we lost a lot of the fruit to mice. They're like kids, taking just one bite out of each big Brandywine, making it unsalable. Anything I can do this year to improve the odds?


A. The absolute best way to minimize the damage to your fruit and vegetables is to grow them vertically!  This will increase your yield SUBSTANTIALLY in several ways - not just less damage from pests.  Learn about vertical growing in the Mittleider Gardening Method books and CD's. 


I recommend The Mittleider Gardening Course, Let's Grow Tomatoes, Grow-Bed Gardening, Gardening By The Foot, and The Garden Master CD.  Tomatoes and Grow-Bed are out of print at the moment, and the best way to buy the whole library is to get the Mittleider Gardening Library, with 9 books and 9 manuals.  It's available at www.growfood.com


Other - more difficult and less effective "traditional" ways to control these pests are discussed below.


There are several ways of reducing damage from voles and mice. We will discuss them by category:
Cultural Methods and Habitat Modifications
Weeds, ground cover, mulch, and litter provide food and cover for voles (as well as bugs and diseases). Eliminating all of these from within the garden, including 3-5' around the perimeter, will reduce the support they provide.


Tilling your soil will also reduce vole damage by removing cover, destroying existing runway burrow systems and killing a percentage of the existing population.

Repellents
Repellents containing Thiram or a "hot sauce" type of ingredient may afford short-term protection, but cannot be relied on for long-term solutions.

Toxic Baits
When the vole population is high or when they cover large areas, toxic baits may be the quickest and most practical means of control. Zinc Phosphide is used most often. It is a single-dose pelleted toxicant, and is broadcast at 6 to 10 pounds per acre, or placed by hand in runways and burrow openings. ZP Gopher Bait is recommended by some as the best zinc Phosphide bait to kill voles.

Anticoagulants interfere with an animal\\\\'s blood-clotting mechanisms, eventually leading to death. While these are perhaps the safest rodent bait for use around homes and gardens, because they are slow acting they must be consumed over a period of 5 or more days to be effective. Place the bait in runways or next to burrows so voles will find it during their normal travels,
baiting every other day for at least six days.


Trapping
For smaller or concentrated populations, trapping may be effective. For a small garden a dozen traps is probably the minimum number required, but for larger areas 50 or more may be needed. A simple wooden mouse trap is often used, baited with a peanut butter-oatmeal mixture or apple slices. If strategically placed in their runway, no bait may be needed because voles will trigger the trap as they pass over it. Place baited traps at right angles to the runways with the trigger end in the runway. Examine traps daily and remove dead voles or reset sprung traps as needed. Continue to trap in the same location until no more voles are caught, then move the trap to a new location 15 to 20 feet away. Destroy old runways to deter new voles from moving in.

Exclusion
Quarter-inch Wire mesh fences at least 12" above the ground, and 6-10" deep in the ground, will help to exclude voles from entire gardens. Eliminating all weeds for at least 3' on the outside of the fence will further increase its effectiveness.

Protect young trees, vines, and ornamentals from girdling using cylinders made from hardware cloth, sheet metal, or heavy plastic, such as plastic soda bottles. Make them 1) wide enough to allow for tree growth, 2) in areas with snow, tall enough to extend above snow level, and 3) buried below the soil surface enough to prevent the voles from digging under them.


Repellents
The effectiveness of commercial repellents is questionable and their use is often not practical because 1) voles usually damage plants at or just beneath the soil surface, so adequate coverage is difficult or impossible; 2) they must be applied before damage occurs, and 3) unless use on food crops is specified on the product label, repellents should never be applied in a vegetable garden.


Biological Control
While predators such as coyotes, foxes, badgers, weasels, cats, gulls, hawks and owls all eat voles, in most cases these will not solve the gardener's problems. Reasons include: 1) Most do not hunt close to homes and gardens. 2) They have a broad-based diet and shift to other prey when the number of voles declines. 3) Predators rarely remove every vole, and any remaining voles can re-populate an area in a short period.

Other Control Methods
In our opinion, burrow fumigants are not effective for the control of voles because the vole's burrow system is shallow and has numerous open holes. Electromagnetic or ultrasonic devices and flooding are also considered to be ineffective against voles.