http://www.nbcnews.com/id/40254997/ns/technology_and_science-future_of_energy/#.Ui-OudKUSDo

By Jennifer Viegas
11/18/2010

Home gardeners often struggle to prevent deer from eating prized roses and other plants, so how do commercial Christmas tree growers keep hungry deer at bay? North Carolina State University extension researchers have recently come up with some creative, natural, and cost-effective solutions.

The scientists, led by Christmas tree production specialist Jeff Owen, are exploring the use of inexpensive, inedible food byproducts — such as dried blood and egg powder — typically sold in bulk to the pet food industry to be used for flavoring. These byproducts cost 85 to 90 percent less than their commercial counterparts, and are found to be just as effective.

Using these repellents, which can be purchased locally in bulk, may provide tree farmers an early Christmas present.

“These products have an unappealing taste, but the decaying smell actually elicits a fear response in the deer and keeps them away from the crops,” Owen explained. “We’re continuing to look at similar products, like liver powder and fishmeal, to see if they work the same way.”

The products add to the growing list of more well-known natural repellants, such as human hair clippings, cayenne pepper, and raw eggs.

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For home gardeners who might wish to also benefit from Owen's research, he offers the following tip:
“Our growers get these products in 50-pound bags or even 2,000-pound pallets, and have to mix the egg powder or dried blood into a solution to be sprayed. It’s not the prettiest process,” he laughed. “For the average homeowner, the pre-made commercial deer repellent should be more than adequate, provided you rotate repellents from time to time.”