Deer can cause two types of damage to plants: rubbing or battering by antlers and browsing. Battering usually occurs prior to the deer’s rutting season, in late summer and early fall, as male deer rub their antlers against young trees, two to three inches in diameter. Rubbing against stems and young trunks can cause girdling and dieback. Browsing may occur throughout the entire year but becomes more noticeable during late fall and winter when other foods are less available. A hungry deer in a cold winter will eat anything and one adult deer can consume up to four pounds of woody twigs a day.
Management for Deer Damage
Fencing is the most reliable deer control solution, but not always the most practical or aesthetically pleasing. Deer are good jumpers and it is commonly recommended to use at least 8-foot high fencing. Metal cages placed around individual plants will help deter deer from browsing, provided the cage is tall enough to prevent deer from reaching over the top. Protecting trees with plastic collars and tree guards in late summer will protect trunks from deer rubbing. Be sure to remove wrapping in spring to avoid damage to the trees. Several commercial repellents are available for short-term solutions. Spray repellents work by emitting an odor or taste that deer don’t like. Their success is based on the level of reduction of feeding and not on totally eliminating deer browsing. Reapplication is necessary in inclement weather.
Mice or Moles
These small rodents do most of their damage during the winter when they gnaw trunks and roots, usually below snowline. Subsequently, the damage causes a slow decline and eventual death of the plant.
Management for Mice and Moles
The success to removing mice lies in taking action before damage occurs. In autumn, look for nests or mouse runs in grass and other vegetation close to the soil surface. Push mulch directly away from the base of trees and shrubs. Place cylinders of hardware cloth (1/4-inch mesh) around plants; be sure to extend cylinder deep enough into the soil to prevent mice from digging under the screen. Commercial repellents, such as those recommended for rabbits, will usually work against mice.
Rabbits damage plants by eating small twigs and buds or chewing bark at the base of plants. The clipped twigs exhibit a clean, 45 degree slant or knife-like cut. Trunk damage is often scarred with paired gouges from the rabbit’s front teeth. Rabbits generally feed no more than two feet above the ground or at snow level. Small plants can be severely altered or reduced in size.
Management for Rabbits
One of the best ways to protect against rabbits is to secure a fence of chicken wire or wire mesh around plants needing protection. The fencing needs to be at least 18-to-24-inches high and should be buried into the ground about 2-3 inches to prevent tunneling underneath. Individual cylinders of hardware cloth or commercial tree wrap can protect valuable trees from damage. The cylinders should extend above the expected snow line and stand one or two inches from the tree trunk.
Chemical repellents discourage rabbit browsing, but only protect the parts of the plant they contact. New growth that emerges after application is not protected. Heavy rains may require reapplication of some repellents. Scattering dried bloodmeal or napthalene mothballs will discourage rabbits in small garden areas.
The yellow-bellied sapsucker is a member of the woodpecker family. This migratory bird, about the size of a starling, is present in the Chicago area during April and again in September and October. An individual sapsucker often picks a favorite tree and returns to it repeatedly. Favorite trees seem to be pine, apple, maple, and birch, though it may feed on other species as well.
The appearance of holes on the trunk or branches of trees is often an indication of borers. However, if the holes have a regularly spaced pattern, either as a horizontal circle around the trunk or vertical side-by-side rows, the damage is caused by the sapsucker. Plant injury occurs when the bird feeds on the inner bark, but it may also feed on the flowing sap and insects trapped in the sap. After repeated attacks on the same area of the tree, large patches of bark may be removed. If the area is girdled, the portion of the tree above the affected area will die.
Management for Sapsuckers
It is difficult to prevent sapsucker damage, but to discourage sapsuckers from feeding on a favorite tree, wrap hardware cloth or burlap around the area being damaged, or smear the bark with a commercial sticky repellent, such as “Bird Tanglefoot”. Beware, however, that other birds not responsible for the damage can also get stuck in it.
Squirrels damage trees by clipping, gnawing, and stripping the twigs and bark. Twigs are clipped during the collection of seeds and buds. Their favorite trees in the spring are maples and elms; in the fall they prefer oaks and walnuts. The clipped twigs often litter the area beneath the tree, and the ends of the twigs appear as though they were cut with shears. The bark on larger branches may be gnawed or stripped in winter or early spring when food supplies are reduced. During the summer, squirrels may occasionally strip bark from main stems and larger branches for nesting material. The squirrel is a very crafty animal, so control is difficult and is seldom fully effective.