Here’s a deer repellent trial we all want to know about.
Researchers at Cornell U at Ithaca NY conducted field trials of deer repellants. It was a 10-week trial beginning in early Feb. The target shrub was Japanese yew, a plant favored by deer in this region. Plants were photographed and the images recorded and analyzed for damage on before/after pictures.
- BGR mix and BGR spray: Deer-Away Big Game Repellent (containing putrescent egg solids)
- CU-A: experimental extract (using organic solvents) from Japanese pachysandra (Pachysandra terminalis) leaves (known to be rarely browsed by deer) and 0.25% spreader-sticker
- CU-B: about 70% experimental extract from Japanese pachy- sandra leaves, about 30% synthetic fermented eggs, and 0.25% spreader-sticker
- Deer-Off: (containing putrescent egg solids, garlic, and cap- saicin)
- Deer Stopper II (containing putrescent egg solids and cap- saicin)
- Repellex (containing dried animal blood plasma)
- Tree Guard (containing denatonium benzoate, also known as Bitrex)
- Control (no repellent).
Each treatment was given to 28 plants.
In general, the putrescent egg solids appear to be more effective
Having said that – the most effective repellents will need to be re-applied every 4-5 weeks to remain effective.
Bottom Line. Start spraying early in the winter and keep at it once a month.
Note I originally posted this in 2010. It’s being updated as part of the site rebuild.