Deer Management - an Overview
By Vern Grubinger
Vegetable and Berry Specialist
University of Vermont Extension

We were in the kitchen eating lunch when the dog growled, and my son yelled “there’s a deer in the raspberries!” All of us charged out the door shouting (and barking) while the deer, about 100 feet away, stopped nibbling, gave us a haughty look, then casually turned and with two quick jumps was gone into the woods. At least I hope he ate some raspberry cane borers while he was at it.

Increasing populations.  For a lot of farmers and gardeners, white-tailed deer seem to be causing more and more trouble. That may be because their numbers have been increasing across the Northeast in recent decades. Although deer were nearly wiped out by hunting in the late 1800’s, they have made a remarkable comeback. For example, in New York, the deer population has rebounded from about 20,000 to more than 1 million. Pennsylvania has about 1.5 million deer, or 30 deer per square mile. Changes in hunting practices and land use patterns have allowed deer populations to increase. The fact that deer are prolific breeders helped, too.

Where they live and what they eat.  According to an excellent fact sheet by Cornell Cooperative Extension’s Wildlife Management Program, deer like to live at the edge of the forest rather than inside it. They prefer a mixture of conifers and hardwoods, with shrubs, abandoned fields, and cropland nearby. This type of mixed vegetation provides them will all kinds of food as well as protective cover. But as people in the suburbs know, deer can adapt quite well to a combination of lawns, gardens, and patches of forest.

Deer cause a lot of damage to flowers, fruits, vegetables, and the buds and twigs of fruit trees and ornamental shrubs. Damage to landscape plantings and ornamentals can happen any time of year but it’s worst in late winter and early spring when other wild foods that deer eat may be in limited supply.

It’s pretty easy to tell deer damage from feeding by rabbits or rodents. Rabbits or rodents leave a clean-cut surface on the plant, but because deer lack upper incisors they leave a ragged, broken end on browsed branches. And deer are a lot taller, too, so their damage is high off the ground relative to smaller mammals.

Favorite snacks.  Deer prefer certain plant species over others, and wouldn’t you know it that many of their favorites are valuable species, including a lot of horticultural crops and important trees. Because deer prefer oak and sugar maple seedlings, as well as acorns, to less palatable species like American beech and striped maple, less desirable forest-product species may be more likely to survive to maturity where deer are abundant.

One strategy for minimizing deer damage is to grow plant species that deer don’t like very much. Bleeding heart, daffodil, paper birch and rhubarb are examples of plants that deer tend to leave alone. Of course, I like to grow daylilies, apples, blueberries and raspberries – examples of plants they do tend to damage. Even with undesirable plants, if there are a lot of deer in an area, or if the natural foods supply is limited, they may get munched on. If you want more information about the plants deer do and don’t like, there are lists available from Extension in many states. One good example is Maryland Cooperative Extension’s fact sheet #655.

Blam!  Hunting is an effective way to reduce deer populations and thus damage in rural areas and most states have an annual deer hunting season. However, buck-only harvests won’t reduce or even stabilize deer numbers. Harvesting female deer is essential to reducing deer numbers and deer damage. Without hunting, deer populations will tend to increase. If mortality is low and food is abundant, deer numbers can double in size every two to three years, so hunting is critical to managing the deer population. Obviously, you or the hunters you allow on your land must follow state hunting laws.

Boo!  Scare devices can be used to limit deer feeding, at least for a short time. Such devices include lights, whistles, and loud noises. Using these will not endear you to your neighbors. And anyway, deer get adjusted to most scare devices after a few days.

Yuk!   The timely application of repellents can help prevent deer feeding on crops or landscape plants. Repellents work best in small plantings, and are not usually effective by themselves in commercial plantings because of cost, restrictions for use on some crops, and variable results. It’s important to apply repellents at the first sign of damage, or even before damage occurs, to prevent deer from establishing a feeding pattern.

Deer repellents either taste bad or smell bad. Many commercially available repellents can be applied as a spray to ornamental shrubs and nonbearing fruit trees, but far fewer products are approved for use on vegetables and fruit-bearing trees during the growing season. These include Hinder, a soap-based repellent, and Deer-Off, which contains putrefied egg solids, garlic and other ingredients.

The effectiveness of repellents depends on how many deer there are, how hungry they are, and what you’re trying to protect. If wild food supplies are limited, repellents are less likely to work. Some damage will usually occur with use of repellents, even if browsing pressure is low. In general repellents should be applied when rain is not expected for at least a day, and the temperature will be between 40° and 80° F.

Non-commercial repellents such as bars of soap, cat urine, and human hair may be effective in some cases, but results are very variable, and regulatory agencies prohibit the use of most pest control products unless they are registered by the EPA.

Fencing works.  Where there are a lot of deer, or where valuable plants need to be protected, fencing is the most effective way to prevent damage. Large fences work the best, but cost the most. Smaller fences work better for protecting smaller areas, or when they are combined with repellents.

Permanent, upright woven wire fences at least eight feet high are used to protect high value crops year-round. They’re expensive to construct but effective even where deer pressure is high, last a long time, and are relatively easy to maintain. Non-electric fences usually need to be at least eight feet tall to discourage the deer from jumping over them, and they need to be strong to keep deer from making holes in them over time. The border around the fence should be kept clear of trees or brush so that deer don’t accidentally run into the fence and so that trees won’t fall on it. If any holes occur, repair them quickly so deer don't get use to feeding inside the fence.

Although deer can jump over a 10 or 12-foot barrier, they usually won't unless very hungry or frightened. Some permanent fences are only 5 or 6 feet tall, but placed at an angle rather than upright to provide a visual ‘three dimensional ‘barrier. Fences can also be electrified, providing a psychological barrier, to enhance their effectiveness.

Electric fences may have single or multiple strands and they range from low cost temporary set-ups to high-tensile slanted fences that last many years. Electric fences are intended to get deer to avoid them after being shocked. However, deer are well insulated by their fur and can sometime walk through without being shocked. To assure a shock and thus change deer behavior, it helps to bait the fence with peanut butter. It’s also important to keep the fence area free of grass and other debris that may ground the fence and reduce the charge. Relatively short electric fences won’t provide complete or perfect deer exclusion, especially in high pressure situations, but they can be very effective for moderate-sized fields where deer pressure is moderate.

A simple cotton rope fence used with a repellent can be used to prevent deer browsing in flower beds or small vegetable gardens. Combining a visual barrier like a rope or other small fence plus an odor repellent can reduce browsing considerably during the growing season when alternative foods are available. The fence can be constructed by installing 3- to 4-foot posts around the perimeter of the beds. Attach cotton cord or rope at a height of about 30 inches and spray an odor-based repellent directly onto the cotton rope or on strips of cotton cloth tied to the rope at 3- to 4-foot intervals.

For more detailed information on all kinds of wildlife management, including deer, visit: http://wildlifedamage.unl.edu/handbook/handbook/

11/06
RETURN TO VERMONT VEGETABLE AND BERRY PAGE