KENTUCKY CHRISTMAS TREE PRODUCTION WORKBOOK:
Thomas G. Barnes, Extension Wildlife Specialist, Department of Forestry
University of Kentucky, Lexington, KY 40546-0073
The most common 4-footed animals likely
to become pests in Christmas tree plantations are voles (Microtus spp.),
cottontail rabbits (Sylvilagus spp.), and white-tailed deer (Odocoileus
virginianus). The amount and extent of damage to the plantations varies
as populations of these species vary and the number of tree plantations
Animal Identification and Biology
Often referred to as meadow mice or
field mice, voles are compact small mammals with stocky bodies, short legs
and a short tail. Voles should not be confused with white-footed mice (Peromyscus
spp.) or other small rodents which, because they eat seeds, do not cause
extensive gnawing damage to trees. Three of the four species of voles found
in Kentucky are responsible for tree damage.
Voles eat a wide variety of plants
and other small animals or insects. Pine voles characteristically attack
trees of all sizes during all seasons, in contrast to other voles which
usually damage bark of trees in winter. Most pine vole damage occurs below
ground where they feed on rootlets and the bark of larger roots.
Voles do not hibernate and are most
active during the day. Areas of activity are small (1/4 acre) and depend
on population number, food supply, habitat and season. Voles construct
many tunnels and runways in the dense vegetation. A single burrow system
may contain several adults and young.
Voles breed from January through October
in Kentucky and can produce an entirely new generation within about 60
days. Although voles have a high reproductive rate, they also are a mainstay
in the diet of hawks, owls, foxes, coyotes and other meat-eating animals.
The life span of a vole is short, ranging from two to 16 months. Up to
80 percent of the young die in their first month of life.
People often place the cottontail rabbit
in the same group as the rodents (mice, squirrels, rats) because of their
large prominent front teeth. However, careful inspection reveals that rabbits
have a second, smaller, peglike set of incisor teeth directly behind the
first set. Rabbits are therefore placed into the group called "lagomorphs".
Our most abundant and common rabbit
is the eastern cottontail (Sylvilagus floridanus). Typical eastern cottontail
rabbits weigh between two and four pounds and are 15 to 19 inches long.
Cottontails appear gray to brownish gray in the field with a short tail
and big ears. The underside of the tail is white and looks like a cotton
ball. Hence the name cottontail.
The life span of a cottontail is short
(12 to 15 months); however, cottontails may have three to eight young per
litter and up to four litters per year in Kentucky. The first litter usually
appears in March. Up to 35 percent of the young die within the first month
and 65 percent of the remaining animals die over winter. Cottontails are
eaten by a variety of predators. The cottontail also is one of Kentucky's
most popular small game animals avidly pursued by hunters.
The white-tailed deer is the only native
ungulate occurring in Kentucky. Their general appearance, tan color in
summer with large antlers and conspicuous white flag (tail), is well known.
Contrasted to the previous animals,
deer have a very long gestation period (196 days) and give birth to one
or two fawns, usually in May. Deer breed once a year during November and
December and can live up to 10 years in the wild.
Animal browsing on trees can result
in tree death due to complete girdling of the trunk or roots. Even if browsing
does not kill the tree, its shape can be disfigured by extensive browsing
(especially at terminal buds), rendering the tree unsalable.
Before attempting to prevent or control
wildlife damage, be sure to identify correctly the culprits responsible.
Correct identification is relatively easy based upon evidence at the site
Typical vole damage can be differentiated
from rabbit damage by the lack of uniformity of gnawing marks and the area
of the tree damaged. In addition, gnawing and possible tree girdling usually
occur near the base of the tree. Presence of tracks, droppings and burrow
systems should verify initial assessments.
Characteristic rabbit damage may occur
as girdling near the base of the tree (tooth marks usually visible) or
clipping of terminal buds or twigs. Rabbits clip young tender shoots cleanly
producing wounds similar in appearance to a knife cut at a 45 degree angle.
Presence of tracks and small round droppings usually verify initial observations.
Damage by deer is quite distinctive
because deer lack upper incisors necessary to produce the sharp, oblique
cuts of rabbits or voles. Deer browsing often leaves a jagged or torn surface
on terminal twigs, stems, and buds. In addition, the height of the damage
often rules out any other mammal and deer tracks are very distinctive.
Deer also may damage Christmas trees
by rubbing against tree bark. During late summer and early fall, buck deer
exhibit unique behavioral patterns associated with courtship. Male deer
vigorously "rub" small trees (often less than 5 years old) at this time
to remove the velvet from hardened antlers, practice combat with potential
rival bucks, provide a visual display signalling dominance over other deer,
and scent signposts. Trees may have branches torn off or be effectively
girdled by this action rendering the tree unsalable.
Options for Preventing and Controlling Damage
There are many preventive and control
techniques available for addressing animal damage problems in tree plantations.
Not every one will work in every situation. Each situation must be evaluated
individually and various treatments may have to be tried to determine the
best technique for the particular situation. Often a combination of techniques
produces the best results. For example, in an Oregon study, the best protection
for growing conifers was a combination of a deer/rabbit repellent and plastic
The various damage prevention and control
techniques may be grouped as (1) biological, (2) mechanical or (3) chemical.
Each technique has particular advantages and disadvantages depending on
location, problem animal species and expense.
The most effective, long term solution
to controlling deer and rabbit problems in tree plantations is to reduce
populations through hunting. This method of control is not effective for
voles. Hunting has several advantages over other methods. It is more economical
(may be income-generating), does not place harmful chemicals into the environment,
and is a long-term solution to the problem, not a quick fix.
Deer and cottontail rabbits are legal
game animals in the Commonwealth of Kentucky and can be harvested only
during hunting seasons. If damage is severe enough and a variety of other
techniques have failed, contact your local conservation officer and obtain
a permit to harvest the problem animals at times other than the hunting
season. It is unfortunate to harvest deer or rabbits with a special permit
when many eager hunters would gladly do it, and possibly pay for the privilege
during the hunting season. By permitting hunting, landowners provide public
access to a public resource and at the same time reduce their damage problems.
Deer will travel over several miles
during the course of a normal day or season. As a result, one landowner
rarely controls all the land a deer uses and neighboring landowners should
be contacted and asked to cooperate. The Kentucky Department of Fish and
Wildlife Resources district wildlife biologist should be contacted so that
desirable populations may be reached within state guidelines. Harvest strategies
for population reduction should be directed at removing excess female animals.
The Kentucky Department of Fish and Wildlife Resources or your county Extension
agriculture agent may be able to provide names of hunters willing to pay
for the privilege of hunting. Hunting is the preferred method of control
in most cases.
Another type of biological control
that may work for all three target species is a habitat alteration or modification.
Tree plantations which are clean-cultivated (all sod, grass and weeds are
removed between trees and rows of trees) throughout the growing season
provide little food or cover for voles, rabbits or deer. As a result, trees
in plantations which have no ground cover are not as likely to receive
heavy wildlife damage. If the area can not be tilled, use an appropriate
herbicide to destroy the unwanted vegetation. Once the vegetation has been
killed, remove all dead material. Another technique useful in reducing
rabbit populations is to remove brush piles or junk dumps located close
to the plantation.
A final biological method of reducing
small mammal populations is to install raptor perches (Fig. 7). These structures
provide hawks and other birds of prey an elevated "overlook" where they
stand waiting to catch small animals. To build a raptor perch, you need
10 feet of 1.5- to 2-inch diameter scrap pipe. Attach a house plumbing
flange to the top of the pipe. Attach a 1-foot piece of 2 x 4 onto the
flange perpendicular to the pipe. Set the pipe firmly into the ground stabilizing
it with a fence spacer bar. Predators will come and sit on the perch and
catch their lunch from there. Only one perch per acre or two is necessary;
locate on higher ground to give a better overlook.
This method of control prevents animals
from entering the general area (fencing) or preventing individual trees
from being clipped (tree guard tubes or plastic netting). It is equally
effective in controlling small mammals, cottontail rabbits and deer.
No one fencing design will control
damage from all three species. While fencing is the only sure way to eliminate
animal damage, the cost of constructing effective fences often is prohibitive
and, therefore, not practical. Look at costs and benefits carefully before
investing in this option.
A 5- or 6-wire high tensile electric
fence should keep deer out (Fig. 8). If traditional mesh wire is to be
used, it must be at least eight feet tall and can be constructed of two
hog wire panels joined together and supported with 12-foot wooden posts
(Fig. 9). Materials may be saved with this design (or the electric fence)
by slanting the fence at a 45-degree angle (Fig. 10). The high end of this
fence should be six feet from the ground and slanted so that deer can walk
under it without being able to jump over the wire strands. Be sure to keep
the vegetation around the fence cut. These fences will not be effective
in excluding rabbits and small mammals.
Traditional fencing designs can be
modified easily to exclude rabbits and small mammals by placing a 2-foot
strip of 1/4-inch hardware cloth at the bottom of the fence. Be sure to
keep six inches of the fence below ground. This will prevent voles from
burrowing under it. Inexpensive chicken wire may be placed around the plantation
to keep out rabbits, but it needs periodic replacement.
Another type of exclusion device is
a plastic tree guard tube or mesh netting (plastic or 1/4-inch hardware
cloth). Each individual tree is covered or enclosed by a plastic device
designed to prevent deer from browsing on the young seedlings (Fig. 11).
The Europeans have cleverly designed
a physical deterrent preventing deer from rubbing their antlers against
small trees. This structure can be made from a 3- to 4-foot length of steel
rebar (a common construction material). Weld several 12-to 18-inch crosspieces
in a spiral arrangement on the original rod (Fig. 12). Drive the completed
structure into the ground next to the trunk of a small tree. The crosspieces
discourage deer from rubbing their antlers on the tree trunk.
Small mammal and rabbit populations
can be reduced using live or snap traps. Live trapping is the most effective
way to remove cottontail rabbits. There are a variety of commercial live
traps available at hardware, agricultural supply or sporting goods stores
(Fig. 13). Live traps are more effective if you cover them with canvas
or some other dark material.
Bait the traps with cob corn, oats,
or dried apples during the fall or winter and carrots, apples, or cabbage
in the summer. Place the traps in areas where rabbits have been feeding
or resting close to suitable cover. You must check the traps every day
and remove captured animals and replace baits. If the traps fail to capture
any rabbits within a week, move them to a different location.
If you have an exceptionally large
population of small mammals, trapping may not be a solution. Small populations
can be controlled using snap traps or Sherman live traps (Fig. 14). Bait
the traps with a mixture of peanut butter and oatmeal or dried apples.
Place the traps perpendicular to the runway with the trigger end in the
Repellents are classified as visual,
auditory (sound) and chemical. Visual repellents include placing brightly
colored or shiny materials around the perimeter of the plantation.
Noise devices have not proven effective
or reliable in preventing or controlling damage from small mammals or cottontail
rabbits. They can be used to provide temporary relief from deer browsing.
The key to using frightening devices (propane cannons or gas exploders,
whistlers, screamers, and fuse ropes) is to take action at the first sign
of a problem and be persistent continuing use for a minimum of three to
five days. It is difficult to break a deer's behavior pattern once it has
been established. Frightening devices may be most effective in the short
term until a long-term solution is decided upon.
The two main groups of chemicals used
to prevent or control wildlife damage are repellents and toxicants (poisons).
Repellents work well in reducing (not eliminating) wildlife damage. As
a producer, you must decide if a 50 to 70% reduction in animal browsing
is sufficient to justify using a chemical repellent. There are no toxicants
registered for use against rabbits or deer; however, toxicants are one
of the best ways of initially controlling vole damage.
Chemical repellents are classified
as either contact or area. Contact repellents are applied directly to plants
and repel by unpleasant taste, whereas area repellents are applied next
to plants and repel by smell alone. Area repellents may be slightly less
effective than contact repellents. It is important to recognize that repellents
will not eliminate damage. They only reduce the severity of the browsing.
The biggest disadvantage of using chemical repellents is cost. Numerous
studies have shown in many cases it is much cheaper to build a fence (which
will be successful in eliminating damage) than it is to continually apply
Repellents should be applied before
damage occurs and must be reapplied after a rain, heavy dew or new plant
growth. Always follow label directions for the repellent you are using.
Never apply repellents to any portion of a plant likely to be eaten by
humans unless the label permits it.
There are a variety of commercially
available chemical repellents on the market today. During the dormant season
apply contact repellents when temperatures are above freezing. If you have
wildlife damage problems during the growing season, apply a contact repellent
at about half the recommended concentration. Commercially available repellents
can be found under a variety of trade names. The active ingredient ln these
repellents is usually bone tar oil, fermented egg solids, ammonium soaps
of fatty acids or capiscin (extract from hot peppers).
Several toxicants are registered for
use in controlling vole populations. When using a poison, take extra precautions
to ensure the safety of children, pets, and nontarget animals. Follow product
label instructions carefully. Never use a pesticide in a manner inconsistent
with its labeling. Failure to comply with directions provided may subject
you to severe sanctions and penalties provided by state and/or federal
Toxicants designed to kill voles are
called rodenticides. Rodenticides are classified as single-dose or multiple
dose depending on how long it takes the poison to act. Single dose (acute)
rodenticides require only one feeding to be lethal. Zinc phosphide is the
most commonly used acute poison. It is a restricted use pesticide. Any
person using this pesticide must be certified by EPA or work directly under
the supervision of a certified person.
Zinc phosphide is a highly toxic stomach
poison that kills rapidly. Bait shyness can develop if only a small amount
of bait is eaten. If this happens, voles will not eat any bait for 6 months
or more. To avoid this situation, do not use zinc phosphide more often
than every 6 months and always follow label instructions.
The best method for controlling voles
in plantations is to use zinc phosphide as the primary treatment. The appropriately
registered multiple dose rodenticide (anticoagulant poison) should be used
as a secondary or follow up treatment. Anticoagulant rodenticides are slow
acting because voles poisoned with these chemicals die from internal bleeding.
Thus, they must be consumed for several consecutive days to be effective.
Because voles must feed on the bait for 3 to 5 days, it must be available
for an extended period of time. Be sure to place the bait in runways or
next to burrows so voles will find it during their normal travels.
Weather can affect success or failure
of any outdoor toxicant control program. Voles are less active during periods
of bad weather so fewer animals may come in contact with the poison. In
addition, light rains can wash the toxicant off of grain baits and heavy
rains can turn pelleted baits into mush. To minimize the effects of weather,
bait stations (shingles or boards placed in a v shaped structure, 2- to
3-inch diameter plastic pipe, or commercially available station) should
be established throughout the plantation.
Once initial control has been established,
remaining voles can be eliminated by trapping or spot-baiting with an appropriate
toxicant by hand. To prevent further problems from developing, the habitat
should be modified. A minimum suggestion for habitat modification would
be to remove all vegetation within a 3-foot radius strip or circle next
to each tree base.
Rodenticides are highly toxic and hazardous.
Care should be taken in their storage, handling and application. Vole baits
are poisonous to warm-blooded animals (mammals, birds, pets, children)
or they would not be effective against voles. Before using any of these
materials, read the container label instructions carefully. Observe all
cautionary statements. In addition, follow these safety guidelines:
1.Post all treated areas. Even if signs
are not required, they serve as a courtesy as well as a warning to individuals.
2.Store all rodenticides or repellents
in closed storage areas (following label instructions) which can never
be accessible to children or pets.
3.Never drop or leave empty containers
where they are accessible to children, pets or wildlife.
4.Always carefully read and follow
rodenticide label instructions.
Contact your local county Extension office for more information on using
toxicants to control voles.
Vandalism. Vandalism, most commonly
thievery, is a constant problem for Christmas tree growers. Generally growers
write off the loss of a few trees per year. The danger to be aware of is
large scale tree removal when trees are big enough to harvest. Constant
monitoring of your plantation from Thanksgiving to Christmas is your best
protection. Notify and ask neighbors and police to assist you. (Provide
them with free trees as added incentive; good public relations never hurt
anyone!) Some growers enclose their plantations with barbed wire or electric
fences. Some use video cameras as a deterrent. These are displayed prominently
along an electric fence. If the circuit is broken whoever or whatever breaks
the circuit is captured on film or tape.
Another alternative is to spray your
trees with a product resembling flocking, making them highly visible and
identifiable. This product washes off easily when you are ready to market
your trees. A bizarre solution is to get vials of methyl mercaptan (skunk
essence) from a scientific supply house. Carefully attach open vials to
several trees. They probably will cause the whole area to have a distinctive
odor deterring prospective thieves.
At this date, the laws are not clear
on crop insurance for Christmas trees. This insurance, when available,
also would be a protection against crop loss by theft.
A good dose of common sense and constant
vigilance are still the best protection against any type of pest in your
Christmas tree plantation.
Where trade names are used, no endorsement is intended, nor is criticism
implied of similar products not named.