Pepper sprays used to repel and kill insects contain the active ingredient capsaicin, the chemical name of which is 8-methyl-n-vanillyl-6-nonenamide. It appears to disrupt the nervous system and damage cell membranes of insects and mites. The Environmental Protection Agency (EPA) lists it as a biochemical pesticide. The EPA first registered it as an insecticide in 1962; it is also registered as a miticide.
Pepper sprayed on plant foliage deters feeding by lace bugs, spider mites and other insects. Liquid dishwashing liquid is often added to help the spray cling to leaves. Hot pepper spray is considered an appropriate insecticide for use by organic gardeners.
Several dozen pepper sprays marketed in the United States are used to repel insects; others are used to repel deer, rabbits and other animals. They come in granular formulations, liquids and aerosols.
Pepper Capsaicin Content
Capsaicin is a phenylpropanoid compound, a substance some plants manufacture to keep them from being consumed by plant-eating animals. Capsaicin used in pepper sprays is obtained from plants in the genus Capsicum that are important to the cuisine of Mexico, Thailand, South Korea and other countries. The strength of a home recipe for pepper spray depends on the amount of capsiacin the peppers contain.
The capsaicin content of peppers is measured in Scoville units. Of the peppers commonly available in North America, Anaheim peppers contain 500 to 2,500 Scoville units; jalapeno peppers contain 2,500 to 8,000; serrano peppers have 10,000 to 23,0000; cayenne peppers have 30,000 to 50,000, and habaneros range from 100,000 to 359,000.
Pepper Spray Recipes
The Sierra Club recommends dropping three to four chopped hot peppers or 2 to 4 tsp. of Tabasco sauce or hot pepper powder into boiling water. Remove the water, let it steep for 24 hours, and then add 1 qt. of cold water and two drops of biodegradable dish washing liquid.
An agronomist from the University of Florida suggests a simpler spray recipe: Mix 2 tbsp. of hot pepper sauce and six drops of dish washing liquid to 1 gallon of water.
A spray recipe from India, said to repel ants and other insects, is to boil 2/3 cup of chopped hot peppers in 3 cups of water and then strain the mixture.
If dried hot pepper powder is used to make pepper spray, care should be taken not to inhale it. If capsaicin is inhaled, it can cause the lungs to swell. Capsaicin can irritate eyes and the mucous membranes of the mouth.