Trico: a novel repellent for preventing deer damage to ornamental shrubs

Homeowners whose landscape plants are repeatedly browsed by white-tailed deer (Odocoileus virginianus; deer) desire repellent products that are effective and long-lasting. We conducted a 12-week trial from January 6 through April 5, 2021 to test the duration and efficacy of a novel deer repellent (Trico((R))) relative to Plantskydd((R)), a commonly used deer repellent, and untreated plants. We placed treated and control Japanese yew shrubs (Taxus media 'Hicksii') at 4 homeowner sites (Birch Hills Drive, Fairview Crescent, Pinegrove Ave., and St. Paul Blvd.) near Rochester, New York, USA, where we detected deer presence. Yews are frequently eaten by deer during winter and provide a good bioassay for testing repellents. To gauge the efficacy of the repellents, we photographed the yews and scored the level of deer browsing. We used ordinal logistic regression to determine the change in efficacy over time. Trico deer repellent reduced deer damage to yews (chi-square = 97.273, P < 0.0001). Damage to yews treated with Plantskydd did not differ from control plants (chi-square = 0.24, P = 0.621) after 12 weeks. The performance of deer repellents varied considerably among sites (chi-square = 109.460, P < 0.0001). Where there was intense deer browsing pressure (Pinegrove Ave. site), both repellents failed to protect the yews. However, at 3 of 4 sites, the Trico repellent effectively protected yews from deer browsing during winter through spring green-up in April. We found Trico to be an effective, long-lasting repellent for protecting ornamental shrubs from deer browsing during winter.