Effectiveness of deer repellents in Connecticut

Browsing by overabundant herds of white-tailed deer (Odocoileus virginianus) can cause signifi cant economic damage to agricultural crops and landscape plantings. In many instances, for both commercial growers and homeowners, commercially available repellents may be an appealing alternative to physical exclusion and lethal control of animals. We tested 10 different commercially-available repellents (Chew-Not®, Deer Off®, Deer-Away® Big Game Repellent, Plantskydd®, Bobbex®, Liquid Fence®, Deer Solution®, Hinder®, Repellex® systemic tablets, and coyote urine) on yews (Taxus cuspidata Densiformis) at 2 different locations in Connecticut. The study included both positive (fence) and negative (no treatment) controls. We planted yews in 2 blocks at each location in the spring of 2006; each block had 12 groups of 6 yews. We randomly assigned one of the 12 treatments to each group of yews within each block. We applied repellents based on manufacturers’ label recommendations for the 2006 and 2007 growing seasons and recorded application costs. We derived a protection index based on plant size and dry needle weights at the end of the 2007 growing season. In general, repellents that required more frequent application performed better. Bobbex® ranked highest, but was the most expensive repellent treatment. Hinder® performed nearly as well at a fraction of the cost. Yews protected by Repellex®, Deer Solution®, coyote urine, and Plantskydd® were the same size as unprotected controls at both sites and did not have signifi cantly more needles. No repellents prevented 100% of browse damage. The choice of repellent usage is a trade-off among effectiveness, cost, ability to follow recommended reapplication interval, and plant to be protected.