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Managing Deer Damage Using a Two-Tiered Fence System

Deer damage to crops occurs every year on small farms and strawberry fields. Damage done by feeding and trampling (figure 1 and 2) limits the number of healthy plants (figure 3) and may reduce crop harvest below needed or projected yields.

More growers are diversifying and adding high value cash crops, like strawberries, to their farms that can cost upwards of $6,940 per acre to establish.1 Strawberries are one of the few crops that are green during the late fall and winter months, making them a prime food source for deer.2 Many growers seek solutions to keep deer out of their crops. Deer damage can be limited by using several different tactics, including deterrence. One of the more successful deterrence methods is exclusion fencing, and perhaps the most effective and economical method is the two-tiered fence system.

Figure 1. Deer tracks on strawberry plastic

Figure 1. Deer tracks on strawberry plastic

Figure 2. A deer damaged strawberry plant in early February

Figure 2. A deer damaged strawberry plant in early February

Figure 3. Healthy strawberry plants

Figure 3. Healthy strawberry plants

The two-tiered fence system works by having two fences (inner and outer) offset from one another (figure 4), which creates a three-dimensional barrier that deer are hesitant to cross due to their poor depth perception. The first or outer fence is electrified to serve as an additional deterrent.

Setup

Ensure there is a minimum of ten feet of space from the crop perimeter to the outer fence to provide adequate space for the two tiers of fencing. The perimeter of the crop and the inner fence should be spaced five feet apart (figure 4a), and the inner and outer fences should also be spaced five feet apart (figure 4b), to create drive rows for mowing.

Once a perimeter is established around the field, poles for the inner and outer fencing should be spaced fifteen feet apart (figure 4c). The poles of the outer fence are connected by one strand polytape 1½ feet to 2 feet off the ground (figure 4d). Polytape is a ribbon of woven plastic and metal that can transmit voltage from a charger and deliver an electric shock upon contact. Polytape is used due to its lightweight nature, ease of installation, and tendency to flutter in the wind, which provides additional deterrence. There are many brands and several widths of polytape to choose from. The key to choosing the correct size is to make sure the tape is highly visible to deer. In some cases, small deer, raccoons, or other small mammals may crawl underneath the first fence. If this is the case, the first fence can be lowered to a height that will deter animals from crawling under the fence.

The inner fence should have two strands of polytape; the upper strand should be five to ten feet above the ground (figure 4e), and the lower strand, two to four feet above the ground (figure 4f). Additional strands of polytape may be added to both the inner and outer fences if necessary. The two fences should be connected with polytape intermittently (figure 4g) to maintain an even current throughout the fencing.

A fence charger consisting of a solar cell panel and an energizer is used to conduct an electrical current to the polytape (figure 4h). The solar panel should be facing south to capture the most sunlight. Alligator clips or other connectors are used to attach the negative wire from the charger to a grounding rod nearby and the positive wire to the closest polytape strand (figure 4i). Multiple grounding rods, connected to each other, will ground the system better and increase the output of the shock. In lieu of a solar charger, a car or marine battery may be used to provide electricity to the energizer (figure 5).

Figure 4. Diagram of a typical two-tiered fence system. Illustration credit: Walker Massey, Clemson University.

Figure 4. Diagram of a typical two-tiered fence system. Illustration credit: Walker Massey, Clemson University.

 

Figure 5. Fence charger with a battery (instead of a solar panel) to provide electricity to the energizer

Figure 5. Fence charger with a battery (instead of a solar panel) to provide electricity to the energizer

A metal tab with a dollop of peanut butter can be added to the outer fence to encourage deer to come to the fence. When a deer tastes the peanut butter, the fence will deliver an electric shock, training the deer to stay away. In areas with heavy deer pressure, fencing and baiting with peanut butter should be set up before the crop is planted, to ensure deer have experienced a shock.3

Fence Maintenance

Regular inspections and maintenance of the fencing should be carried out to ensure it is clear of any debris including weeds, grass, sticks, equipment, plastic bags, etc that could ground the fence out, leaving it with no electricity. The fence should be checked regularly with a digital voltmeter to ensure that the shock delivered is strong enough to discourage deer from crossing, a minimum of 3,000 volts is recommended.4,5 Since fencing may be unplugged to allow workers to enter and exit without experiencing a shock, it is important to remember to check that the fence is on after the last person exits the field. Two-tiered fences can be temporary or permanent, remaining in place for crop rotations throughout the year for several years.

Assessing Costs

The materials required to fence in a one-acre field that measures 100 ft x 440 ft are included in table 1. Costs are based on the average pricing of three online retailers in 2019, but the materials are most likely also available from local suppliers. Some costs can be reduced by using materials already on hand and by increasing the spacing between poles. In lieu of fiberglass poles – tomato stakes, PVC pipe, bamboo, wooden posts, and t-posts can be used to help offset cost. Growers can experiment with different materials, spacing of poles, and number of strands of polytape to ensure fencing is economical and effective for their operation (figure 6).

Table 1. Average material pricing from three online retailers to construct two-tiered fencing on one acre

Materials Amount Average cost per unit Average cost for 1 acre
½-inch polytape 1320 ft per roll (3) $49 $147.00
6ft corner fiberglass poles 8 $5.96 $47.68
6ft In-row fiberglass poles 136 $4.00 $544.00
Insulators for polytape 216 (1 insulator per pole on outer fence and 2 on

inner fence)

$0.20 $43.20
Grounding rod 1 $16.60 $16.60
Solar charger energizer kit 1 $164.66 $164.66
Digital voltmeter 1 $28 $28.00
$991.14 (Total cost)
Figure 6. Usage of multiple layers of polytape

Figure 6. Usage of multiple layers of polytape

The price analysis for fencing should be spread out over a minimum of five years or more depending on how well the fence is maintained.6 The price per acre for fencing will decrease as more acres are added, as one energizer can power many acres depending on the model purchased. Assuming one strawberry plant produces 1½ pounds per plant, and fresh market value is $2.00 per pound, one plant’s production can be worth $3.00. On most farms growing strawberries, there are between 13,000 and 17,400 strawberry plants per acre.1 It would require 330 plants or less than 3% of the total population of plants being saved in one season to recover the investment in a two-tiered fence to exclude deer.

References Cited

  1. Poling EB, Hoffman M. 2019 Strawberry Plasticulture: A grower’s guide to production, economics and marketing. Siler (NC): The North Carolina Strawberry Association; 2019.
  2. University of Massachusetts Amherst, The Center for Agriculture, Food and the Environment. Amherst (MA): Preventing deer damage. [accessed 2019 Aug 6]. https://ag.umass.edu/vegetable/fact-sheets/preventing-deer-damage.
  3. Indiana Department of Natural Resources. Managing deer damage. Indiana (IN): State of Indiana; C2019 [accessed 2019 Aug 6]. https://www.in.gov/dnr/fishwild/2718.htm.
  4. PennState Extension. The Pennsylvania State University. University Park, (PA): Orchard wildlife – Integrated management of white-tailed deer. [accessed 2019 Aug 6]. https://extension.psu.edu/orchard-wildlife-integrated-management-of-white-tailed-deer.
  5. VerCatuteren KC, Lavelle MJ, Hygnstrom S. From the field: Fences and deer-damage management: A review of designs and efficacy. Wildlife Society Bulletin. 2006 Mar; 34(1): 191-200.
  6. Pierce RA. Controlling Deer Damage in Missouri. University of Missouri Extension. 2019 Jan. [accessed Aug 2019]. https://extension2.missouri.edu/mp685.

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