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To: Mr. Chris Pearmund, Winemaker and Managing Partner, La Grange Winery

From: Richard Delage

Date: 31 March, 2008

Subject: Preventing Crop Loss Caused by Deer

Summary:

Winery crop losses that are the result of deer infiltrating the vineyard are an ongoing and vexing problem to your vineyard and vineyards throughout North America. Having a herd of deer break through a deer fence and eat many of the new vines can be devastating to any new vineyard or winery. A hungry deer will find almost any plant palatable, but the smell of new vine shoots in your relatively young vineyard is an especially attractive food source. The grape growing industry is quickly embracing a new “Electrified Peanut Butter Fencing” solution. This product consists of installing a repellent combined with baited and electrified deer fencing. Using this three-fold strategy has been showing great promise for vineyard managers in reducing deer damage and crop loss.

Problem:

Some vineyard owners have begun referring to the cute white tail deer as the new “rat” of the 21st century. Deer populations have been expanding through out North America and, in particular, rural areas, with rat-like rapidity. Deer predation in vineyards used to be limited to browsing on the tender shoots of young vines in early spring. Recently deer damage has expanded to the consumption of ripe grapes on a wholesale level. The problem of deer damage to high value crops, like grapes, is bordering on epidemic. Grape growers can only expect this problem to get worse, because there is no sign of any substantial decline in deer population in the near future. Additionally, it is not only the deer that are nipping at tender young shoots and vine ripened grapes, but also wild turkey, raccoons, birds and the occasional bear. All of these hungry animals are vying for a taste of your valuable crop, which in turn greatly impacts your revenue.

Recommendation:

The static fencing that you currently have in place at La Grange winery has been proven to have mixed results. When a deer (or other pest) violates the existing perimeter fencing of the vineyard, the only recourse you now have is to hunt and remove the culprit. Hunting, though, is not always a safe, effective, or acceptable solution in many situations, especially in urban and rural areas. A better fence is available that can be an effective long term, year round solution to deer damage. Detailed analysis given at the Fifth Eastern Wildlife Damage Control Conference has shown a remarkable 99% effectiveness. It keeps deer at bay by combining three highly effective methods that had been previously employed separately. These methods merge the use of a vertical 3-wire electric fence modified with the use of peanut butter attractant and the deer repellant “Jersey.”

Evidence:

In the Fifth Eastern Wildlife Damage Control Conference report, the use of a non-electric fence (similar to your current fence) was the least effective because “deer either, crawled under, went through, or jumped over it with little difficulty. The addition of electricity clearly increased effectiveness of the design. A possible drawback of electric alone is that many times deer going through the fence contact the wire with insensitive parts of their body resulting in a shock too mild to deter” (Jordan, Par. 17). The number of deer invasions into an electric alone fence and an electricity plus peanut butter fence was substantially different. The basic idea is that deer are attracted to bait stations around an electrified fence. When deer lick the peanut butter bait, they are shocked with a short 5000 volt burst. This shock trains the deer to stay clear of that area. However, in studies, some deer still persisted in entering, which suggests that these deer did not investigate the peanut butter and simply entered the fenced area. Another possibility is that some of these deer did receive a shock when investigating the peanut butter but associated the pain only with the peanut butter and in the future entered the fenced area avoiding the peanut butter altogether.

An electric fence combined with using the repellant “Jersey” was also highly effective and in some cases more effective than peanut butter baits. Jersey is a safe inert spray, using all natural ingredients, that smells terrible to deer but peppermint fresh to humans. The combination of using electricity and Jersey repellant provides a second level deterrent. If a deer ignores the repellant and continues on, then it will receive a shock deterrent. This will cause the deer to avoid the fence in the future because it is treated to dual averse conditioning.

The most successful deer management strategy appears to be the combination of these three avoidance methods using an Attractant, a Repellent, and an Electric shock (ARE) for vineyard fencing. The Jordan study revealed that “Deer appeared to exhibit a conditioned avoidance of the [electric] fences equipped with peanut butter and Jersey” (Jordan, Par. 21). The use of an electrified fence modified with the use of peanut butter bait stations and the use of Jersey spray repellant clearly provided the highest degree of deer avoidance. It would seem that what smelled bad (the repellant) really was bad, and a shock was administered if the bad smelling area was still ignored. It also seems that what smells good (the peanut butter) was also bad in that one lick delivers a 5000 volt shock to the nose or tongue. The following diagram shows how to add peanut butter bait stations to existing electrified fencing (Nuyaka). The double sticky back adhesive tape holds the aluminum foil in place. A quantity of peanut butter is then placed under the foil, with the foil now protecting the peanut butter from the rain. If a poly-tape or poly-rope electric wire is used, then a water thinned solution of peanut butter can be applied directly to the poly tape/rope at the height of a deer’s nose.

Typical Electrified Peanut Butter Fence

The following table was taken from a study entitled EFFECTIVENESS OF A VERTICAL 3-WIRE ELECTRIC FENCE MODIFIED WITH ATTRACTANTS OR REPELLENTS AS A DEER ENCLOSURE . The table gives a synopsis of an extensive study performed by Don Jordan and Milo Richmond. Their results show that the ARE fencing is clearly superior, with no apples having been eaten in the 116 days of the trial.

Table 1. Deer encroachment by fence design at study sites near Ithaca, New York, 1990-91.

Fence Design Exposure Instances of Apples taken

Days Deer Damage by Deer

Control (no fence) 116 37 328

Electric 116 13 79

Attractant & Electric 116 9 59

Repellent & Electric 116 1 8

Attractant, Repellent & Elec. 116 0 0

(Jordan)

Routine monitoring of fence perimeters is required with all types of designs. In rare instances almost any fence will be breached. If an animal is being chased by a predator, it will crash through or damage any design while trying to save its own life. The ARE fencing showed no deer damage during the test period, but in actual usage some damage has occurred. Monitoring of fence integrity combined with renewing the repellent and peanut butter will still need to be done at regular intervals.

Evaluation:

The need for complete deer exclusion is a must in winery vineyards and requires the use of the highest efficacy fencing available: the ARE fence. After reviewing the available scientific studies and cost to benefit ratios, it is apparent that implementing an ARE fence makes sound business and financial sense. Not only is this approach highly effective in deer exclusion, but the added costs of including peanut butter bait stations and spraying with Jersey repellent to an existing electric fence are minimal. This approach will also significantly reduce the need to shoot the wayward interloper and immediately have to deal with cleaning and storing a harvested deer. Even though initial costs to install an ARE fence are high ($4-6.00 per running foot), the ongoing savings received over the 30-year expected life span of this fence are substantially greater. A long-term evaluation of the costs versus savings clearly sides with installing an ARE fence from the outset, with initial costs being recouped within the first five years.

Works Cited

Jordan, Don, and Milo Richmond. “Effectiveness of a Vertical 3-Wire Electric Fence Modified with Attractants or Repellents as a Deer Enclosure.” Fifth Eastern Wildlife Damage Control Conference (1992) 5: 44-47.

Nuyaka Creek Winery. “The Electrified Peanut Butter Fence” © 2008 http://www.nuyakacreek.com/

VerCauteren, K. C., Michael Lavelle and Scott Hygnstrom. “A Simulation Model for Determining Cost-Effectiveness of Fences for Reducing Deer Damage.” Wild Life Society Bulletin (2006) 34: 191-200.

VerCauteren, K. C., Michael Lavelle and Scott Hygnstrom. “Fences and Deer-Damage Management: A Review of Design and Efficacy.” Wild Life Society Bulletin (2006) 34:16-22.