Rabbits, mice and deer can cause a great deal of damage to ornamental and shelterbelt tree plantings. Some methods of damage prevention and control are listed below.
Repellents: There are a number of ready-made repellents on the market that will discourage rabbits, deer and mice from feeding on trees. Most contain thiram, a distasteful but harmless fungicide. Once applied to the tree, its bitter taste discourages animals from taking a second bite.
Repellents should be applied in late fall when the leaves have fallen and the bark of the tree is dry. Apply the repellent on a dry day when the temperature is above freezing. Repellents may be applied with a paint brush, or diluted and applied with a pump-up or knapsack sprayer. Treated plants should be protected for one season, however, new growth will not be protected.
For control of mice damage to stems, coat the base of the plants thoroughly. Rabbits will feed on all parts of the plant so the entire tree should be treated to two to three feet above the snowline if possible. For large trees, concentrating on the terminal growth trees to a height of six feet above the snowline will be cheaper. Young trees should be treated completely.
For winter, apply repellents at about half the recommended summer concentration to save money.
Skoot, Arborgard Rodent Repellent, Willson's Rabbit Repellent and others can be purchased at garden centres or nurseries which carry garden aids, or you can make your own repellent from one of several formulas below.
Note: Most contact repellents are not recommended for use on plant parts that are to be used for food or feeding purposes. See product label for additional safety precautions when spraying.
- Mix one part Thiram wettable powder with ten parts by weight, of water emulsifiable asphalt. This can be painted on the bark of trees.
- To protect trees from sunscald as well as rodent damage, add 2 1/2 lbs. of Thiram 75 WP to two quarts water and slowly blend mixture into a gallon of white exterior latex paint.
- Dissolve seven lbs. of pulverized rosin in one gallon of denatured ethyl alcohol. Keep the container in a warm room for 24 hours to allow the rosin to dissolve, stir occasionally. Do not allow the mixture to be contaminated by water and do not apply heat to it. One gallon will protect 200 to 300 two to three year old trees using backpack sprayer on dry trees.
- Dissolve 666 grams (1.5 lbs.) of Thiram 75 WP into ten litres (two gallons) of water before adding one litre (one pint) of Wilt Pruf. Mix solution well prior to applying. Clean sprayer immediately after use.
Tree Guards: Individual tree guards may be more effective where rabbit damage is concerned. Tree guards can be made from 10-20 mm square wire screen, set 7.5-10 cm into the ground and braced away from the base of the tree. It should reach a height of 50 cm above the expected snowline.
Wrapping trunks of trees with burlap or sisal kraft paper will prevent deer damage as well as protect the tree from sunscald. This will prevent deer from girdling the main trunk of the tree but will not stop them from eating the branches.
To protect trees from mice damage tree guards made from rolled roofing, sheet metal or 1/4" galvanized hardware cloth can be used.
Commercial tree protectors are available from most garden centres. Biodegradable plastic mesh tubing or solid plastic sleeves are two varieties particularly useful for young, single-stemmed seedlings. They should be staked out from the base of the plant.
Habitat Manipulation: Rabbits and mice are key prey species for many mammalian and avian predators. Because of this they rely heavily on vegetative cover for protection. Removal of such hiding cover will reduce the number of rabbits and mice attracted to an area and any that are attracted will be more visible to predators.
Fencing: Fencing is a common control method that is particularly useful when small areas such as orchards or shelterbelts are being damaged. Deer fences can be expensive but represent a good, long term solution to tree and garden damage in areas where deer are prevalent.
- Five Strand Deer Fence: This low-impedance electric fence uses five smooth 12-gauge high tensile wires and a low-impedance electric charger. The wires should be stretched to 250 pounds tension. Place the bottom wire ten inches above the ground and the other four 12 inches apart.
- Peanut Butter Deer Fence: A less expensive temporary system is a single strand electric fence that repels deer by shocking them after they sniff a 12 inch piece of aluminum foil and fold on the outside of the tape so that the flag becomes a 6 × 6 inch piece of foil. As the deer approach the fence they sniff the peanut butter inside, touch the foil, and receive a shock.
- Fencing for Rabbit Control: Small mesh chicken wire fencing can be used effectively to keep rabbits and other small rodents out. The wire must be trenched into the ground and be high enough to be well above the expected level for drifting snow. For control of rabbits in summer a three strand electric fence can be built more cheaply. Use fine wire placed at four, eight and 12 inches above the ground.
Thus one means of reducing rodent problems is to keep the area between and within tree rows, free of weeds. Clearing or mowing adjacent fence rows, brush piles or other vegetative borders around the tree planting will also help.
In some cases, providing an alternate source of food away from the tree planting may reduce problems. For example, plant a strip of winter wheat for deer, away from the trees. Spraying a mixture of water and molasses onto foliage away from your tree planting will make treated trees sweeter and hopefully more attractive than your own.
Pesticides or Trapping
If you cannot put up an effective barrier or repel the animals, the last step is to remove them using traps or rodenticides. Unfortunately, in areas where rabbit or mice populations are high, little can be accomplished with these methods. In fact, in some cases it may make the problem worse. Studies have shown that while the use of rodenticides is very effective in eliminating small mammals in an area, reinvasion from the surrounding area will occur within a few weeks. The ecological vacuum created by the poisoning leaves an abundance of food for the new invaders and often leads to reproduction at an above normal rate. Thus, one can end up with more mice than one had prior to poisoning.
If you must poison, it should be done in late fall when small mammal populations are at their peak, and before girdling damage to trees begins.
Note: In many provinces it is illegal to poison rabbits or hares. Poisoning of any animals can pose a danger to nontarget wild and domestic animals that might feed on poisoned carcasses. If you must poison, every effort should be made to collect dead animals and bury or burn them.