Sunday, January 2, 2011

Deer Country 4: Do Repellents Work?

Do deer repellents really work? Do they keep bambits from eating your greenery?

If you discuss deer browsing with your neighbor, one of her first questions probably will be how you keep deer away. Here are some of the repellents people have mentioned to me: human hair clippings scattered about; strong-smelling bath soap hung strategically in bars or scattered as shavings; smell stations incorporating coyote or other predator urine; and sprays based on foul-smelling or offensive-tasting ingredients.

One gardener told me she spreads shavings of Irish Spring soap around her flowers—and deer stay away. Another gardener said that doesn’t work for her. Another gardener told me he sprinkles urine where deer usually enter his garden—though I suppose it’s difficult for most gardeners to catch a coyote or bobcat and even more difficult to get it to urinate in a bottle so you can dribble it around your hostas.

A shrub grower gave me his personal formula for a spray: Add white and yolk of one egg to one quart of water in a blender, whiz it thoroughly and then some, strain it, and then spray it on plants you want to protect. Theory: the egg putrefies in place on the leaves and repels the browsers. A homeowner gave me a similar formula that used only the yolk but adds one teaspoon of baking powder. She suggested that the mix is more effective if allowed to “ripen” in the sprayer a few days and said it is more pleasant to apply when her husband does it. She warned against using it on edibles.

That warning is well taken. Never apply anything to edibles unless the product is certified for such use. Common sense says anything tainted by raw, rotten egg, for instance, could mean a trip to the hospital, or worse.

Researchers testing such suggestions generally conclude that any repellent may work for a while, until deer get used to it, rain washes it away, or food is so scarce deer ignore the repellent and eat the plant.

Home remedies aside, commercial repellents abound. Most are based on ingredients that the deer don’t like to smell or taste, such as garlic, hot peppers, or rotten eggs. They’re available at your local nursery or big-box store. Researchers have tested some in controlled conditions. Do they work?

The general answer is that repellents do work. But that answer comes with a lot of asterisks. For example, they work best where deer pressure is low and feeding damage light. Because of their cost, they are more practical for small areas and where alternative food is available. Some need to be reapplied periodically or after heavy rains—something homeowners may not do, especially in winter, when browsing is heaviest. And what repels deer in one area may not in another.

If you want to learn about repellents in more detail, I recommend that you read the 12-page University of Maryland Extension Fact Sheet 810, “Using Commercial Deer Repellents to Manage Deer Browsing in the Landscape.” The Fact Sheet compares popular repellents and describes tests of eight during the winters of 2000 to 2002. During those tests, deer browsed 49% of unprotected plants and 18% of plants protected by repellents.” To read it, print it, or download it free, CLICK HERE.

I admit that I’ve had poor results with repellents, including a stinky spray and one that looked like petroleum grease. But maybe I was the problem. I didn’t go out in the winter months to reapply the repellents when needed.

The next two Deer Country postings will discuss deer and vegetable gardens.

Note: Repellents in photos courtesy of River Hill Garden Center, Clarksville, Maryland 21029.

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