Extension Research Note - RNS2



Use of Dogs Contained within Off-Limits Crop Protection System for

Reducing Deer Damage to Orchards and Horticultural Crops


Deer damage to apple trees in commercial orchards is a major problem for growers in Maryland and surrounding states. The use of dogs contained within Off-Limits Crop Protection Systems has been shown to be an effective way to reduce deer damage in orchards in New York State (Rieckenberg and Curtis, 1996). Demonstration studies at a Maryland nursery using this fencing system have been effective (Kays, 1996), but there is no study in Maryland orchards to document the effect of dogs contained within Off-Limits Crop Protection System. The use of this system provides the added benefit of protection from damage by fox and groundhogs.

To test this system in a controlled research environment this fencing system was installed around the 30-acre main orchard areas at the Western Maryland Research and Education Center. The distributor sourced the dogs from Humane Society animal shelter and provided instruction on training the dogs to the fence. The breed and individual dogs are selected to meet the needs of the site. The cost for each dog was $150 to cover direct costs. The project had the dual objectives of:

1) Reducing deer damage to assure that credible research can be completed; and

2) Demonstrating to agricultural producers the effectiveness and utility of this type of fencing system.

Study Design:

Four groups of five Gala apple saplings were planted on November 20, 2000 at the Western Maryland Research and Education Center. The saplings were purchased from Adams Nursery in Pennsylvania. Two groups of five trees were planted in two separate areas within the protected area, and two groups of five trees were planted outside the fenced area. Browsing and seedling damage were assessed in November 2001and in January 2002 using three measures:   

        Visual qualitative assessment;

        Physical measurements such as basal diameter, seedling height, and crown area, at the time of planting and after one growing season; and

        A quantitative assessment to measure seedling coverage area against a white board from a digital photograph taken from a fixed point at the time of planting and after one growing season. 



 In general, trees protected by the fencing system resulted in significantly lower mortality, increased height growth, increased basal diameter growth, increased tree volume, and better form, compared to trees that were unprotected (Table 1).

The pair of dogs in the fencing system also controlled other problem wildlife species. Between July 25, 2000 and August 31, 2001, the dogs killed approximately 45 groundhogs and 17 raccoons, as well as unknown number of voles.

The site was visited again in late January 2002 and 100% of the unprotected trees were dead. The only deer damage visible to the protected trees was one stem that had a branch removed due to a buck rub.

One dog did escape the orchard on a few occasions and cause some problems with neighbors. Dogs must be checked regularly and some inconvenience should be expected to take care of a dog that escapes, veterinary needs, etc. This system is best for people who like dogs.


Table 1. Growth of Protected and Unprotected Gala Apple Trees

After One Growing Season - November 2001

Tree Measure

Protected Trees

Unprotected Trees

Difference between Protected & Unprotected Trees

Tree Survival




Terminal Leader





Trees with Apples (%)




Basal Diameter (cm)



0.41 (20%)

Total Height (m)



0.47 (28%)

Height Growth (m)


- 0.21


Tree Volume (m3)



0.82 (59%)


1) The use of this fencing system was very effective for protecting high-value crops in an orchard or nursery application. Some browsing of fruit trees and vines were found around the perimeter of the protected orchard, but it was minor. In our demonstration, the trees outside the fence were all dead due to browsing and rubbing. In a larger orchard more trees would likely survive, but the results reinforce the effectiveness of this fencing system.

2) When compared to the long-term cost (20-years) of a conventional 8-foot wire mesh fence, the cost is significantly less (See Appendix A). Access to a conventional fencing system is also very complicated due to the need for gates. The initial cost of the Off-Limits Fencing System is relatively low, with annual costs of about $750 per year incurred for feeding and medical care of the dogs. This is in contrast to a conventional fencing system where all the cost must be incurred up front.

3) The control of groundhogs, raccoons, and voles is a significant advantage for fruit growers that have problems with these species of wildlife.

4) A disadvantage of the Off-Limits Crop Protection System is that constant care of the dogs is necessary and some tinkering with the system is needed. If the landowner is not fond of dogs and their care, this may not be the system for them. Over the first year, one dog did escape three times and kill a few chickens belonging to another landowner. The installation of a more powerful collar solved the problem for many months but the dog did escape once more. Initially, two automatic feeder stations were installed, but the dogs tended to frequent only one, so one was removed, and moved around the orchard to encourage movement to more remote sections. Water was provided by an automatic waterer that was heated during the winter so that it would remain in working order.

5) The pair of dogs live in the orchard year-round. Some people find this objectionable but when the needs of the dogs are met (food, water, companionship, health, etc.) they are quite happy in their territory and protect it aggressively. It is possible that one of the dogs will not adapt staying within the fence or will not aggressively deter the deer. In this case it may be necessary to work with the distributor to find a home for the existing dog and source another dog.

Comparison Cost for Dogs Contained by Buried Electric Fence and Conventional Wire Mesh Fence

Area Protected: 33 acres


Initial Cost:

Unit with collars & dogs


9,000 feet fence wire ($0.26 per foot)


Dog house, automatic waterer & feeder, misc.




Annual Costs: food & vet care


Total Cost over 20 years: Initial plus annual costs


Cost per Acre:



Initial Cost:

1,200 linear feet on each side = 4,800 linear feet @ $6 per linear foot installed

(Gates, maintenance, and other items would be additional cost)


Cost per Acre:


Difference in cost per acre:


For more information on deer fencing options and other management techniques contact your local Maryland Cooperative Extension office and purchase a copy of Managing Deer Damage in Maryland (EB354) Cost $2. The information is also available online at http://www.naturalresources.umd.edu/.

For more information on Off-Limits Crop Protection System contact the manufacturer at 800-875-8071.


        Rieckenberg, R. and P. Curtis. 1996. Use of dogs contained within Off-Limits Crop Protection Systems for reducing deer damage to apple orchards. Preliminary program report. Cornell Cooperative Extension, Ithaca, NY.

        Kays, J.S. 1996. Use of dogs and invisible fencing to keep deer out of crop areas. Pg. 19-24. Ed: D.M.  Johnson and K.L. Everts.  In: 1996 Profitable Agriculture and a Clean Environment Update. UMCP Maryland Cooperative Extension, College Park, MD.

       Kays, J. S. (2000). Managing Deer Damage in Maryland. (Extension Bulletin 354). College Park, MD: UMCP, MCE. 20 pp. Cost $2.


        Principal Investigators: Jonathan S. Kays, Maryland Cooperative Extension, George R. Welsh, Maryland Agricultural Experiment Station

        Cooperators: Jim Dowden, Off-Limits Fencing Systems, Cumberland, MD. 800-745-4376; email [email protected]; Ron Clark, Clark Distributors, 703-502-8550

        Funding: Provided by a special grant from the Maryland Agricultural Experiment Station

January 2001

Prepared by: Jonathan S. Kays, Regional Extension Specialist, Maryland Cooperative Extension, Western Maryland Research and Education Center, Keedysville, MD 21756. Email: [email protected]; 301-432-2767 ext. 323.