Evaluating SeaDust Wildlife Controllant™ as a Repellent to Reduce Deer Browse on Douglas-fir Seedlings

Herbivory by black-tailed deer affects growth form and survival of conifer seedlings in western Oregon and Washington, especially Douglas-fir. Several deterrents have been employed to reduce damage to forest resources yet most are ineffective or cost prohibitive. Use of chemical repellents is socially appealing because they offer a potential non-lethal alternative to reduce plant damage (i.e., browse). Commercial deer repellents may employ one or more mechanisms in their formulation, which affect taste, odor, visual, and/or tactile cues when consumed by deer. I evaluated the commercial SeaDust Wildlife Controllant™ as a tool to repel black-tailed deer from Douglas-fir seedlings during spring bud burst in western Oregon (mid-May through early July), because its ingredients have the potential to employ multiple avoidance mechanisms targeted on tactile, taste, and odor cues. Evidence indicated that deer browse was affected by an interaction of treatment and site; therefore, sites were evaluated separately. Treated seedlings were browsed less by deer than untreated seedlings on 2 of 3 tree farms where percent browse ranged from 0.08%-0.17% in treated plots and 0.15%-0.37% in control plots. Browse was similar at the third tree farm (0.15%). However, number of seedlings browsed in the third tree farm was greater than one site and less than the other, suggesting that statistical significance may not represent biological significance in this study. Future research is needed to incorporate acceptable loss to browsing and cost:benefit analyses