Protecting Young Trees From Deer Damage
By Jim McKenna, Brian Beheler, Don Carlson, and Lenny Farlee
Browsing by deer on planted and naturally regenerated hardwood seedlings is one of the greatest obstacles to seedling establishment in many parts of the central hardwood region. Research on tree plantings in Indiana shows that only 60% of planted trees survive five years after planting. Seedlings that are repeatedly browsed by deer can die due to the stress of repeated defoliation or can be out-competed by weeds or other trees and shrubs that are less palatable to the deer. Young trees that grow above browse height are still at risk of being destroyed during the fall rut as male deer rub their antlers on trunks and stems, a condition known as “buck-rub.”
Research on deer-browse preferences and a survey of foresters and wildlife biologists in Indiana indicate that oaks are a preferred tree species for browse by deer. Research also indicates that other valuable tree species like black cherry and black walnut can be damaged by deer browse and buck rub. If you would like to protect your trees from deer damage and your planting has more than 250 trees on half an acre or more, a plastic-mesh, deer-exclusion fence is an effective, cost-efficient barrier to consider (Figure 1). When properly installed and maintained, these fences can reduce deer browse by 60% to 98%, leading to increases in height growth and improved survival during the 6- to 8-year effective lifespan of the fence (Figure 2).
Tree tubes, wire cages, electrified fences, and repellant sprays can all effectively deter deer browse. However, these techniques can be very expensive on a per-tree basis when plantings have several hundreds to thousands of trees. All methods require annual maintenance to remain effective. Tree tubes and cages can make early pruning and weed control difficult along with harboring rodents and wasps. Tree tubes and cages require additional hand labor to remove once the trees have grown beyond deer pressure. Individual tree tube or cage prices are fixed per tree, while the cost of an exclosure fence decreases on a per-tree basis as the acreage planted increases. Current pricing estimates are about $1.50 per linear foot for materials. Determining the cost per tree for individual tree protection techniques will help you determine at what number of trees a fence is cost-efficient.
Plastic Mesh Deer Fence
Researchers at the Hardwood Tree Improvement & Regeneration Center (HTIRC) and other university and private foresters have found plastic mesh deer fences provide good deer protection during plantation establishment. There are two types of plastic mesh fencing commercially available: standard-duty netting in 7.5-foot by 330-foot rolls, and heavy-duty netting that is 7.5-foot tall and 160-foot long, both with a mesh size of approximately 1¾ by 2 inches. The rolls will run about the same price, but the heavy-duty netting is twice the cost per unit length. In our HTIRC research, we typically utilize standard-duty fencing, installing an average of 10,000 feet of fence each year over the last decade.
The standard-duty material will usually last from 6 to 8 years in the field. The heavy-duty mesh is much more durable and provides greater resistance to breaks from events like limb falls and deer collisions. If you would like to reuse the netting after 5 to 8 years for another planting, it may make sense to invest in the heavy-duty netting. The standard-duty fence has been a one-time use for our applications.
Proper placement, construction, and maintenance are critical to fence success. Detailed, step-by-step instructions for building your own durable and effective plastic mesh deer exclusion fence are available online. See FNR-486W, How to Build a Plastic Mesh Deer Exclusion Fence at https://ag.purdue.edu/fnr/Extension/Pages/publications.aspx.
Jim McKenna is the operational tree breeder for the USDA Forest Service, Northern Research Station, Hardwood Tree Improvement and Regeneration Center. Brian Beheler is a woodland properties manager for the Department of Forestry and Natural Resources at Purdue University. Don Carlson is a forester with the Department of Forestry and Natural Resources at Purdue University. Lenny Farlee is an Extension Forester with the Hardwood Tree Improvement and Regeneration Center located at Purdue University.