Efficacy of selected repellents to deter deer browsing on conifer seedlings

Foraging deer can negatively impact agricultural resources. Repellents offer a plausible approach to inhibit browsing. The efficacy of Big Game Repellent-Powder (BGR), Deer Stopper (DST), Plantskydd (PLA) and ECX95BY (ECX) to deter black-tailed deer (Odocoileus hemionus columbianus) browsing of ponderosa pine (Pinus ponderosa), Douglas-fir (Pseudotsugamenziesii) and western red cedar (Thuja plicata) seedlings was assessed during the winter. Extent of damage was expressed as number of seedlings damaged, number of terminal buds damaged, number of lateral bites taken and the number of seedlings with severe damage. BGR, DST and PLA significantly reduced deer damage relative to controls for at least 14 weeks. After 1 week, damage to seedlings treated with ECX was similar to that inflicted on control seedlings. Aversive agents contained in BGR, DST and PLA probably produce sulfurous odors, while ECX contained denatonium benzoate, a bittering agent.