ask-ruth-pictureDear Ruth,

I recently moved to eastern TN from New Mexico/Colorado where many (organic) gardeners use capsaicin spray, powder, or oil from pepper plants (which you can buy easily there at most garden stores) as a good alternative to deter deer, rabbits, squirrels (and less effectively, gophers) from eating plants, and also as a general pest deterrent. I’ve spoken with a few people in the area but haven’t heard or seen it used in this region much. Do you have any more information regarding capsaicinoids and insect control?

Thanks,

Xanda Gordon

Dear Xanda,

Hot peppers (capsicum) are a New World plant originating from South America, probably in the region of southern Brazil to Bolivia. Some people can’t imagine enduring a meal without the spiciness of hot peppers. Hot pepper sauces like Tabasco® inspire legions of loyal followers, and hot pepper fanatics are always searching for the latest pepper with the hottest burn. Gardeners love the instant gratification of whipping up a fresh pepper salsa straight from the garden.

Despite the fact that many humans love hot peppers, capsaicnoids, the “heat” in peppers, is an irritant to mammals and insects. You could even say that (Michael Pollan style) as the hot pepper plant evolved, it favored its heat-producing qualities as a protection for its seed from mammals. Mammals tend to destroy the seed when they chew it, while hot pepper seeds can pass through a bird’s system and still germinate.

Peppers are rated by the Scoville Heat Index ~peppers

  • Sweet Bell Pepper: 0
  • Tabasco® Sauce: 2,500 to 5,000
  • Jalapeno: 2,500 to 9,000
  • Cayenne: 30,000 to 50,000
  • Scotch Bonnet: 100,000 to 350,000
  • Bhut Jolokia “Ghost Pepper”: 800,000 to 1,041,000
  • Common Pepper Spray (used for personal protection): 2,000,000 to 3,000,000

Hot pepper spray is considered a deterrent to insects and mammals, rather than an insecticide. As you can imagine when a rabbit or an insect touches/bites into a leaf/fruit covered with a hot pepper spray, their immediate reaction would be to spit it out and discontinue eating that plant. Hot pepper would certainly be irritating to the insect’s body. Using the Scoville Units indicated above ~ I would conclude that the hotter the pepper used, the more effective the spray is liable to be. However, Jalapeño peppers should be sufficiently hot to do the job without intimidating the preparer. And Xanda, keep in mind that Colorado and New Mexico have drier climates with lower rainfall and scant humidity ~ therefore hot pepper sprays would linger longer on the plants undiluted and demonstrate more effectiveness in dry regions.

Before delving any deeper into this topic, it should be stated that extreme caution should always be exercised when handling hot peppers (whether for use as food or as an deterrent to plant damage). Always wear rubber gloves when handling hot peppers. If you don’t wear gloves, the peppers will burn your hands. The seeds are the very hottest part of the plant. Be careful not to touch your eyes or any other mucous membranes when handling hot peppers. If you are blending the peppers, or cooking them on the stove, beware of the fumes in the air above the blender and in the steam above your pot. Speaking from experience, even something as relatively mild as Tabasco® will volatize in the steam and get in your eyes. When spraying your pepper mixture, don’t spray into the wind.

Local Farmer Feedback on using hot pepper spray:

I asked a few local farmers for their input on hot pepper sprays. A few had never used them at all, or responded like Vanessa Campbell of Full Sun Farm who said they “intuitively felt it didn’t work.”

Barry Rubenstein of B & L Organics said they don’t have rabbit problems, but that they had tried hot pepper spray to control flea beetles one season. They did not have good results, and someone suggested to him that he would have needed to spray almost daily to get good results.

Meredith McKissick of Sweet Earth Flower Farm (and OGS Director) had positive feedback: “I use hot pepper wax as a deterrent for leafhoppers. They are a vector for aster yellows, a common disease that can cripple crops of lettuce, dahlias and asters (among other things). Used in rotation with Pyganic [a pyrethrin spray] I have found it very effective at keeping my dahlias in great condition and weekly sprays to asters and strawflowers have helped as well…I have never used it on lettuce as I am not sure the effect it would have on harvest of the greens.”

Patryk Battle of Sparkling Earth Farm received a bottle of Hot Pepper Wax at a SAC conference years ago and still hasn’t tried it. Several times Pat has “used homemade habanero spray to keep rabbits off my newly emerging legumes. I blend a habanero in a bit of water till it is liquefied. I leave the lid on the blender for at least 15 minutes to be sure no habanero is breathed in by anyone. I strain it and then spray it with enough water to effect coverage. I usually use a surfactant or at least soap to make it last a bit. Although others who have tried this have reported mixed results, I have always stopped my rabbit problems first try. However I have always applied early ~ usually after the first sign of predation on my legumes.”

Reports on hot peppers as a deterrent are mixed. Rodale’s Chemical-free Yard & Garden states that “…Researchers have found that as little as 1/25 ounce of capsaicin [powder] sprinkled around an onion plant reduced the number of onion maggot eggs laid around the plant by 75%, compared to a control plant. Purdue University Extension’s Organic Vegetable Production researchers found that plant extract repellent products (such as hot pepper wax) “work poorly if at all, and we generally do not recommend them.” In a Cornell University test on broccoli transplants, Hot Pepper Wax was found to be as effective as Rotenone 5% on controlling flea beetles (this test was on transplants only and not a field test on larger plants). According to Clemson University, capsaicin can be used on ornamentals ~ outdoors and indoors ~ for control of aphids, spider mites, thrips, whitefly, lace bugs, leafhoppers, and other pests…they appear to be effective at repelling certain animal pests such as rabbits, deer and squirrels. University of Massachusetts-Amherst Extension points out that Hot Pepper Wax is no longer allowable for Certified Organic growers. The National Organic Program allows capsaicin, the active ingredient in Hot Pepper Wax; but does not allow the wax in current use.

wax(photo at left: Commercially Available Hot Pepper Preparation.)

Hot Pepper Sprays may target: rabbits, squirrels, deer, aphids, spider mites, whiteflies, cabbage loopers, beet armyworms, leafhoppers, and other soft-bodied insects that feed on the leaves, flowers, fruit and stems of plants. It seems to deter squirrels and rabbits better than deer.

Other Cautions: Some plants are extra-sensitive to pepper spray, such as basil, parsley, peppermint, African violets with variegated leaves, fruit trees in the pink-bud stage, and Bleeding Heart (Dicentra exemia). It is best to test your spray on a small area of plant material before applying to the entire crop. Hot pepper spray should be applied in the evening so it has all night to dry before the suns rays hit the plant in the morning. Spray the entire plant, paying special attention to the undersides of leaves. If you are using Hot Pepper Wax, the cool evening temperatures will allow the wax to harden on the plant overnight (and become transparent.) Remember that hot pepper spray will not protect new growth, and can also be harmful to beneficial insects. There is a zero hour re-entry after spraying hot pepper. Even though hot pepper wax washes off easily with warm water, some plants ~ like lettuce ~ may wilt when washed with warm water.

How often to spray: Reports differed substantially on this question ~ from repeat after rain, dew, or heavy humidity; to repeat every few days; to repeat in 7 to 10 days; to lasts up to 30 days. The wax product will probably last longest…up to 30 days. If you are making your own spray without wax, add dish soap or a surfactant to encourage the hot pepper to stick on the plant longer.

Homemade Hot Pepper Spray Recipe:
Remember to use rubber gloves and caution when handling hot peppers (see above).

  • 5-10 Hot Peppers depending on size (from your garden or the market, or substitute powdered cayenne pepper)
  • 1 teaspoon pure Soap (dish soap is OK, but not detergent types)
  • 1 tablespoon of Vegetable Oil
  • 6 or more cloves of Garlic (Optional)
  • 1/2 gallon Water, or up to 1 gallon (use 2-3 cups in blender)

Put ingredients in the blender. Add 2-3 cups water. Blend thoroughly until liquefied, adding more water if necessary. Let stand one hour. Liquefy again. Let mixture sit until fumes have settled. Strain (through cheesecloth, coffee filter, paper towel). Dilute with additional water and spray on plants in the evening (using caution at all times when handling the material and during sprayer clean-up). Extra material can be stored in a jar in the refrigerator for a couple of weeks.

Xanda ~ welcome to the southern Appalachians and good luck with your gardening efforts in this area.

Best wishes,
Ruth

Ask Ruth © 2013 Ruth Gonzalez & Organic Growers School

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Ruth Gonzalez

Ruth Gonzalez

Ruth Gonzalez is a former market farmer, current gardener, and local food advocate. She has written numerous local food and gardening articles, blogs about local food, and writes the “Ask Ruth” Gardening Column for Organic Growers School. In her job at Reems Creek Nursery, Ruth offers advice on all sorts of gardening questions, and benefits daily from the shared wisdom of local gardeners. She has a special affection for clouds and finds delight in the natural world at every turn. Read more from Ruth at her blog: http://tailgatemarketfanclub.wordpress.com/