A repellent is a distasteful or foul-smelling chemical that an animal avoids. Commercial repellents are more effective than home remedies such as human hair, soap, feces, or animal remains. These home remedies have been concocted in hopes of keeping deer out of crops, but they realistically offer little relief from the problem.
When using repellents always follow the manufacturer's directions and label instructions before applying a chemical repellent. Never apply repellents to any portion of a plant likely to be eaten by humans unless the label permits it.
Repellents containing 37% putrescent whole egg solids as an active ingredient are available as sprays or ready-to-apply powders. They are used on fruit trees prior to flowering and ornamental trees during the dormant season. These repellents should be applied to new growth and are claimed to be effective for two to six months.
Thiram is a fungicide that acts as a taste repellent. It can be sprayed or brushed on trees. You can make your own thiram-based repellent by combining 2 quarts of 42% thiram, 1 gallon water, and 2 quarts Rhoplex AC-33 as a sticking agent.
There is a chemical repellent registered for use on edible crops. The active ingredient is 15% ammonium soaps of higher fatty acids. It can be applied as a spray to fruit trees, vegetables, field crops, ornamentals, nursery stock, and forage or grain crops. There are other commercially available repellents including those with an active ingredient of 97.5% bone tar oil, 2.5% capsaicin, and benzyldiethyl ammonium. Reapplication of repellants is usually necessary every 2-4 weeks so before you decide to use repellents, conduct a cost/benefit analysis of all possible solutions. If you are having repeated heavy deer damage problems, it may be more cost effective to build a fence than to continually apply repellents.