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leaves with a lighter shade of green than normal.  Dig
around the base of the tree and examine roots for vole
damage. Try additional hand baiting with zinc
phosphide-treated apples. Place bait in as many vole runs
and tunnels as possible. The best times for baiting are in
October and early November. Where voles are not
numerous, thorough coverage of the orchard block may
not be necessary. Treat adjacent fencerows or grassy areas
along with the portions of the orchard in which trouble
usually occurs. During heavy, persistent snow cover, a
few voles can cause serious damage. Thus, it may be
necessary to rebait in midwinter. Place bait in snow
tunnels, air holes, and near fresh bark damage.
Weather.To achieve proper vole control with zinc
phosphide bait, wait until the weather is likely to be fair
and dry for at least 3 days. Zinc phosphide breaks down
and washes off in damp weather. Orchard baiting followed
by rain is generally ineffective.
Many types and brands of tree guards are available
commercially. The tight spring like plastic wraps are not
recommended as they can girdle trunks in later years,
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delay hardening off of the trunk tissue and provide a safe
haven for borers. Mesh type guards rather than solid
plastic are also preferred so that pesticide sprays can reach
the trunk. Voles are good diggers, thus burying the wire
6 inches (15 cm) will deter them from burrowing under
the cylinder. At the very least the guards should be
anchored at the base with some soil or round pea gravel.
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Rabbits can damage young trees, especially during
the heavy snow cover of winter. They feed on the bark,
which can girdle the trees. Maintaining a well-groomed
orchard floor and eliminating brush piles in and adjacent
to orchards should eliminate nesting sites and help to
reduce the population.
These should be installed when trees are first
established. Avoid using the tight wrap around plastic
guards, as they may harm trees. In several orchards, the
use of plastic guards has increased borer infestation in the
trunk. They may also prevent the trunk from hardening
off properly in the fall and, therefore, predispose the tree to
winter injury.
Fine, wire-mesh screens are effective as rabbit and
mouse guards. Hardware cloth can also be used. Several
companies are now manufacturing a plastic-mesh screen
that will decompose after 3 to 4 years in the orchard. Do
not allow debris to accumulate inside these screen guards
as this creates an ideal environment for borer infestation.
All guards should be anchored at ground level. A
good way to do this is with several shovels of pea-sized
gravel, placed inside and outside the guard. The gravel
will also deter mouse injury and will keep the young trees
from whipping a hole in the ground during a windstorm.
The pea-sized gravel trickles down around the trunk and
keeps the tree firmly anchored.
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