Nowhere do deer and man live closer and nowhere is man more affected by deer than on the farm. As much of our land is in farms, the farmer is important in the lives of deer. In turn, deer affect--for better or worse--the farmer and his crops.

Deer have fed on agricultural crops since the first settlers planted fields on their homesteads. In Colonial days deer populations were relatively sparse, farms were small, families were large and no part of the farm was left unattended for long. Damage by deer could ordinarily be controlled, and was offset by substituting venison for the lost crop. Today deer have adapted to the interspersed farm and woodland scene; herds are large, agricultural production is more complex, and deer damage to crops is both widespread and locally severe.

Recent surveys of natural resource managers and farmers defined the distribution and extent of deer damage to agriculture. Deer damage crops on 62 percent of Pennsylvania farms. Major losses occur in corn, forages, and small grains, all of which are grown commercially throughout the Commonwealth. Orchards, nurseries, and vegetables, grown in restricted areas, also are heavily damaged. The annual crop loss to deer is between 16 and 30 million dollars. Distributed evenly over all agricultural production, this represents a small proportion of total value. But the uneven distribution of damage caused by local herd size, proximity to forested deer range, and land use patterns that limit deer hunting, result in excessive losses for individual growers on a variety of crops.

The conflict created by costs to landowners and benefits to hunters and businesses is not helped by excessive numbers of deer and maturing forest growth. These forces lower the capacity of woodlands to support deer and increase the extent of feeding on high-value crops. This situation also results in excessive browsing on new growth within the forest.

Deer management programs aim to maintain the number of deer that can be supported by the range and to provide deer for recreational benefits. An ideally balanced deer herd would practically eliminate excessive and inequitable damage. But this objective is virtually unattainable because of deer distribution, interspersion of farms and woodland, and conflicting land use practices.

Control

Hunting. Regulating hunting, under a flexible system that takes into account changes in range and deer numbers, strives to remove enough deer from the herds to approach a balance. Hunting removals decrease the risk of excessive damage, and extra hunting pressures should be encouraged where crop damage occurs.

Shooting. Persons engaged in commercial agriculture are permitted, at times other than the hunting season, to shoot deer causing crop damage. When planning to protect crops by this method, be sure to contact your local Game Commission District Game Protector to insure understanding of regulations and procedures.

Repellents. Chemical repellents have always been a popular method of keeping deer out of gardens, orchards, and other farm crops. Unfortunately, their effectiveness has not matched their enthusiastic use. While one grower reports success with a particular repellent, his neighbor has none; what seemed to work last year does not this year. Over the long run, the use of repellents has been time-consuming, labor intensive, and costly. Generally, repellent results have been poor.

A comprehensive list of deer repellents was scientifically evaluated using captive deer at the Penn State Deer Research Facility. Included were both commercially-produced registered deer repellents and "home remedies" such as human hair, creosote, and tankage.

Only Big Game Repellent (Deer-Away) provided significant protection. Additional testing, under field conditions, is needed to fully evaluate its effectiveness before widespread use can be recommended. It is registered for use on fruit trees, nurseries, ornamentals, and conifer seedlings, all during the dormant season. Big Game Repellent cannot be used on food crops.

This does not mean that repellents will not work in a particular damage situation. However, some deer may be discouraged but others may not; variable deer numbers and feeding pressure will have an effect. An important factor is that repellent use is limited to specific crops, and most repellents cannot be used on food crops. For most agricultural deer damage in Pennsylvania, repellents are impractical because of high cost, limitations on use, and variable effectiveness.

Fencing

Eight-foot deer-proof fence. To effectively exclude deer, an 8-foot high barrier is needed, requiring 2 widths of 4-foot woven wire and 12-foot posts. Materials and construction costs for this deer-proof fence are prohibitive for most large areas. When constructing this fence, it is essential to keep the wire tight to ground level to prevent deer from crawling under.

Snow Fence. For small areas, such as garden plots, that require seasonal protection from deer damage, conventional snow fencing may be effective. For areas up to approximately 40' by 60', it has been reported to work well, but when larger areas have been surrounded, deer have jumped over such fencing. Snow fencing is lower in cost than woven wire and lends itself to reuse for many seasons.

The Penn State 5-wire electric deer fence. This vertical fence was so named because it was developed as part of a Penn State research project funded by the Pennsylvania Department of Agriculture, and to avoid confusion with other electric deer fence designs. The components, configuration, and construction differ from other electric fences. Growers now have a low-cost, effective alternative to the high-cost, 8-foot woven wire deer fence.

Deer behavior. Deer will usually try to go under or through a fence rather than jump it, even though this could easily be done. They will typically crawl through a 4-foot barbed wire fence rather than jump it. When an attempt is made to penetrate the Penn State 5-wire, the tensioned wire and high voltage insure good shocking power. Thus, deer behavior is modifed and they become trained to avoid the fence. This resulting aversion keeps deer 3 to 4 feet away from the wires; this also reduces their inclination to jump since they normally come within inches of a barrier before leaping over.

Design

Wire spacing and configuration of the 5-wire fence must be followed and materials used should be equivalent to specifications. The bottom wire must be kept approximately 10 inches from the ground while the remaining wires are spaced at 12-inch intervals, making the fence 58 inches high. Electric fences with a wider wire spacing have proven ineffective in excluding deer.

Layout and construction. Laying out lines for electric deer fence is important and should take advantage of level land where possible. Removing underbrush and debris along the line, and grading off humps, eliminates many construction problems and results in a fence that is straighter and easier to maintain. The Penn State 5-wire should never be located directly adjacent to old woven-wire fences, woody fence rows, or brushy cover that deer might normally have to jump to enter a crop field. A 6- to 8-foot open strip should be left outside the perimeter of the fence. Straight lines and the open strip are needed to modify deer behavior; and may require sacrificing a small amount of tillable land or including some non-crop areas within the fence exclosure.

Each straight length of fence begins or ends at an end post, corner post, or gate post which are larger in diameter, longer in length, and are set deeper in the soil than other posts. Construction of brace assemblies at these points is probably the most important aspect of a high-tensile fence because these strong points support the tension on the wires.

Line posts can be smaller and spaced 50 to 60 or more feet apart on level terrain where minimal lateral, upward or downward forces are expected. In curves, and on uneven terrain with dips and rises, more posts are needed to maintain the 10-inch bottom wire spacing. Some of these posts may have to be larger and driven deeper to withstand the added tension stresses created. When laying out the line posts, it cannot be overemphasized to maintain the 10-inch spacing of the bottom wire of this fence.

Once the fence has been constructed and a proper energizer installed, the only potential problem to consider is the possible failure of the fence to deliver sufficient shock. This could only be because of improper grounding. In order for electricity to flow, there must be a completed circuit. For adequate grounding, the fence must have approximately 20 feet of rod or pipe in the soil.

U. S. Steel produces a booklet, "How to Build High Tensile Fences," that is invaluable to a person building such a fence for the first time. It contains most of the information necessary to build the Penn State 5-wire electric deer fence to specifications.

Maintenance. Electric fences are not effective if the current is switched off, if a battery fails, or if the wires are short circuited by heavy vegetation or deep snow. They require inspection and maintenance, especially if a battery-powered energizer is used. The safety module intended to protect the energizer should be checked after lightning storms and replaced if the storm caused failure.

Even with high-voltage, low-impedance energizers, vegetative loads cannot be ignored. These modern energizers can power a fence with a weed load in dry weather, but during wet weather the same weed load can drain enough voltage to reduce the fence's effectiveness. Since top voltage is required to turn deer, a weed control program is necessary for effective damage control. Snow can have the same effect and when it covers the bottom wire or two, the current to those wires should be disconnected.

A voltmeter should be used to check voltage levels regularly. Power output can be determined by a one-location check, thus saving many trips around the perimeter of the fence to look for shorts. Only if the voltage is low is a trip required.

Remember, without electric shock, this fence fails to alter deer behavior and neglect of maintenance may result in deer penetration.

Forest Resources Extension, The Pennsylvania State University,
The U. S. Fish and Wildlife Service Pennsylvania Game Commission