Evaluation of Deer Repellents for Reducing Deer Damage to Christmas Trees

Abstract

White-tailed deer (Odocoileus virginianus) populations are overabundant in many locations in New York State and the Northeast. In such areas, the costs of crop and landscape plant damage continue to rise. Growers and homeowners need reliable repellent products to protect their plant material from deer browsing damage. In past research, efficacy of commercial deer repellents was highly variable, and few products provided reliable protection beyond 4 to 6 weeks at a time when deer feeding pressure was high. We evaluated a new deer repellent (TRICO) registered in Europe that has shown promise for preventing deer damage to trees for up to 6 months with a single spray application. Lack of persistent snow cover, and an abundant fall mast crop, resulted in no deer damage to fir trees on three study farms because of alternative forage available. We did observe deer damage to Fraser fir trees (Abies fraseri) on a fourth farm. Both formulations of TRICO repellent tested, along with a commercial product (Plantskydd), prevented deer damage to Christmas trees on this farm for the entire winter. The control fir trees had an average of 9.5 twig tips missing per tree, compared with 0 twigs missing for any of the repellent-treated trees. Additional replicated field trials are warranted, as these results were very encouraging.