Effectiveness of odour repellents for protecting ornamental shrubs from browsing by white-tailed deer

Abstract Big Game Repellent (BGR), SeaCure (a sulfur-containing topical fertilizer), or 3-methyl-2-hexanoic acid (the principal odour in human sweat) were applied to yews (Taxus spp.), rhododendrons (Rhododendron spp.), or arborvitae (Thuja spp.), and the effectiveness of these treatments as white-tailed deer (Odocoileus virginianus) odour repellents was evaluated. In experiment 1, 16 residential sites were identified, and three plants at each site were selected for treatment. One plant at each site was covered with Deer-X netting, and another was sprayed with an agricultural spreader/sticker (0.14 ml l−1). The third plant at each site was treated with spreader/sticker and one of the repellents. At five sites, SeaCure was applied (8.0 ml l−1). At another six sites, 3-methyl-2-hexanoic acid was applied (0.42 ml l−1). At the remaining five sites, BGR was applied as an even coating (manufacturer's instructions). At each site, plants were approximately 10 m apart. After 6 weeks, only plastic netting and BGR appeared to reduce browse damage. SeaCure and 3-methyl-2-hexanoic acid were ineffective. In experiment 2, ten of the original 16 residential sites were selected. SeaCure and 3-methyl-2-hexanoic acid were reapplied at ten times the concentration used in experiment 1, and damage was evaluated 3 weeks later: neither substance reduced damage. In experiment 3, plants at the remaining six sites were sprayed with BGR or spreader/sticker, or were netted. Plants were spaced ∼30 m apart, and damage was evaluated after 3 weeks. Neither BGR nor netting conferred significant protection.