I have a large property and can’t afford to fence the entire area, which includes many ornamental shrubs and perennials. What are the most effective deer repellents?
We empathize. For a gardener, few things are more frustrating than discovering headless stems the very morning you expect to see full blooms. Even “deer-resistant” plants are sometimes good eats to a hungry deer. No repellent, commercial or homemade, can provide 100 percent protection, but some do work better than others.
After surveying 22 earlier studies of deer repellents and then conducting their own controlled study at two different locations, researchers at Connecticut Agricultural Experiment Station concluded that egg-based repellents worked better than predator urines and blood-based products. Repellents applied more often were more effective than those applied less frequently.
“The sulfurous smell given off by the putrefied egg mimics the smell of rotting meat, giving deer the impression there is a predator in the vicinity,” says Scott Williams, an assistant scientist for the Connecticut Department of Forestry and Horticulture and co-author of the study. “The smell also mimics the scent of urine from a predator who would have likely feasted on another animal. This is the theory behind the use of eggs in all these repellents.” The odor diminishes for humans soon after application, but it lingers for deer, which have a superior sense of smell.
Of the 10 commercial deer repellents tested in the Connecticut study, Bobbex (fish meal, hot pepper, putrid eggs, dried blood, wintergreen oil and more) performed best, achieving 93 percent protection compared with the 100 percent protection of a fence. Soap-based Hinder was the runner-up, with 83 percent protection. Both products were applied every two weeks according to label directions. Hinder, though a little less effective, was less expensive and easier to use.
“When selecting a repellent, consider how much damage you are getting, how much you are willing to spend to control it, and how willing you are to follow the treatment schedule,” Williams says.
What about noncommercial repellents — things such as soap bars, human hair or human urine? “For areas receiving only light deer damage, they can be worth trying, but they generally are less effective,” Williams says. “One home remedy involves mixing four or five eggs and 4 tablespoons hot pepper sauce with a gallon of water, and applying it with a sprayer.” Plan to reapply every 10 to 14 days.
“Whatever measure you take, I recommend rotating several different treatments, because deer habituate quickly — it helps to keep them on their toes,” Williams says. “For heavy deer pressure, only a fence will work.”