Many essential oils exist that have uses as pesticides such as citrus oils, mint oil, pine oil, capsicum (pepper) extracts, tree oils and vegetable oils. The essential oil of Bergamot, Anise, Sage, Tea tree, Geranium, Mint, and Thyme, Hyssop, Rosemary, Thyme, and White Clover can be used to control certain pests on plants. They have been shown to reduce the number of eggs laid and the amount of feeding damage by certain insects, particularly lepidopteran caterpillars.
Sprays made from Tansy have demonstrated a repellent effect on imported cabbageworm on cabbage, reducing the number of eggs laid on the plants. Teas made from Wormwood or Nasturtiums are reputed to repel aphids from fruit trees, and sprays made from ground or blended Catnip, Chives, Feverfew, Marigolds, or Rue have also been used by gardeners against pests that feed on leaves.
How to Make: In general, herbal sprays are made by mashing or blending 1 to 2 cups of fresh leaves with 2 to 4 cups of water and leaving them to soak overnight. Or you can make an herbal tea by pouring the same amount of boiling water over 2 to 4 cups fresh or 1 to 2 cups dry leaves and leaving them to steep until cool. Strain the water through a cheesecloth before spraying and dilute further with 2 to 4 cups water. Add a very small amount of non-detergent liquid soap (1/4 teaspoon in 1 to 2 quarts of water) to help spray stick to leaves and spread better. You can also buy commercial essential herbal oils and dilute with water to make a spray. Experiment with proportions, starting with a few drops of oil per cup of water.
How to Use: Spray plants thoroughly, especially undersides of leaves, and repeat when necessary. Do not use more than once a week on some plants.
Some common botanical pesticides made from essential plant oils are listed below:
Canola Oil - Canola oil is an edible vegetable oil obtained from the seeds of two species of rape plants, Brassica napus and B. campestris of the family Cruciferae (mustard family). It is used to control insects on a wide variety of crops. Canola oil is considered safe for human consumption. Scientists believe that canola oil repels insects by altering the outer layer of the leaf surface or by acting as an insect irritant. Canola oil appears to have no adverse effects on humans or the environment.
Catnip Oil – Research by Iowa State University and the US Forest Service announced that nepatalactone, the essential oil in catnip, can be used as a very effective mosquito repellent. The authors stated that nepetalactone is about 10 times more effective than DEET. The researchers believe that catnip repels mosquitoes by an irritant reaction.
How to make: in a hand-held spray bottle, mix 1/4-1/2 tsp. of essential oil of catnip (Nepata cataria), 1 cup of isopropyl alcohol, and 1 cup of water.
How to use: Shake well and then spray lightly on clothing, arms, and legs, being careful to avoid eyes or open cuts. Do not use on the skin of small children. Some persons may be sensitive to catnip oil. Keep the contents of the spray away from children and pets.
Cedarwood Oil – Cedarwood oil is often used in mothproofing, and may contribute to the control of certain other insects. The US Army tested various forms of cedar, including cedar chips, cedar oil and sachet bags of cedar shavings. Their conclusions were that cedar works best in confined spaces such as clothes storage bins, but had little effect in other applications. A commercial cedar wood oil spray made by Safers® had little residual effect, but works when applied directly to the pests.
Citronella Oil - Oil of Citronella is a volatile, liquid oil derived from dried cultivated grasses. Citronella has been used for over 50 years as an insect repellent and as an animal repellent. It is found in many familiar insect repellent products: candles, lotions, gels, sprays and towelette wipes for use on clothing and people.
These products repel various insects, some of which are public health pests, such as mosquitoes, biting flies and fleas. Citronella is also present in some pellet and tablet products for use around home lawns and gardens to repel dogs and cats.
When used according to the label, citronella products are not expected to cause harm to humans, pets or the environment. It works by repelling animals and insects without harming or killing them. It has a distinctive odor, which repels certain animals. In tablet or pellet form it is also used in recreational areas, outdoor household areas, and around trees and shrubs. Animal collars and tags containing citronella are used on pets and other domestic animals to repel fleas and ticks.
Clove Oil – which can be mixed in a spray bottle with warm water and sprayed where ever you do not want bugs to go. This numbing oil is also good when the pain of a bug bite or sting is bothering you.
Cottonseed Oil – Cottonseed oil is generally considered the most insecticidal of the vegetable oils. Several commercial products are available that contain cottonseed oil, however this oil is not generally available for wide spread use.
Neem Oil - Neem oil is extracted from the tropical neem tree, Azadirachta indica, contains insecticidal properties that are composed of a complex mixture of biologically active compounds. It has a strong, slightly garlic-like odor that some people describe as unpleasant. Its various active ingredients act as repellents, feeding inhibitors, egg laying deterrents, growth retardants, sterilants and direct toxins.
Neem has both contact and systemic action in plants. The active ingredients biodegrade rapidly in sunlight and within a few weeks in the soil. Neem oil has very low toxicity to mammals. Clarified hydrophobic extracts of neem oil are used to control some fungal diseases of plants. In India, neem products have been used in toothpaste, pharmaceuticals, and as a grain protectant for centuries without apparent harm to humans.
Patchouli Oil – whose botanical name is pogostemom cablin, can be used to stimulate new cell growth, tightens tissues, speeds healing of sores, wounds, reducing body odor, cools fever, and repels insects.
Tea Tree Oil – Keep a spray bottle mixed with 15 drops of Tea Tree Oil and a quart of water to repel insects close by. In the summer ants tend to come in our patio door or along the exposed wall. When that begins, spray this natural Bug Buster several times a day for several days and they’ll find somewhere else to go. Natural doesn’t work fast like chemicals, but then it doesn’t kill a little bit of you either!
Specific Insects and What Works
Ants – Several drops of Peppermint oil may be sprinkled strategically along counters and walls to deter ants. It is very important to test surface area to make sure the oil will not destroy the finish. Water may be used as a base to make up a spray for areas where ants like to gather. Add 4 oz. of water into a spritzer bottle and add 20 drops of Peppermint, Citronella or Spearmint oil to give repelling power.
Dust Mites – Mix 5 drops of Eucalyptus oil to the rinse cycle of your
washing machine. Into a spray bottle add 8 oz. methylated spirits and 40 drops Eucalyptus oil. Add 6 oz. water and lightly spray under beds.
Fleas – Pennyroyal oil is specific against fleas. For a spray, place 20 drops into a spray bottle and add 4 oz. water. One to two extra drops of Cedarwood, Citronella, Lemongrass or Lavender may also be added. Lightly spray your animal (without saturating and avoiding eyes) and its bedding areas.
Use 10 drops of Tea Tree Oil to 8 oz. of water and spray on animal’s coat as you rub it in. It will be good for their skin also. This needs to be done daily until the problem is under control in the home. After all fleas are gone you can put it in a spray bottle and give your animal a spritz all over once or twice a day if fleas are in the area.
Ticks and Leeches – Apply Tea Tree Oil to the live tick or leech and surrounding skin. Leave for 20 minutes. The tick may fall off. If not, remove it carefully (make certain no part of the tick is left in the skin). Continue applying the oil to the bite three times per day for up to seven days.
First Aid: Insect Bites and Stings
For blue bottles-mozzies- midgies-sandflies
10 drops Lavender oil into Aloe ointment or gel – Dab directly onto bites or stings for soothing relief.
Insect Repellant Spray
For mozzies-midgies- sandflies – In a Spritzer Bottle
Shake well before using and lightly spray onto exposed skin areas. Do not use during pregnancy.
1. Bio-Integral Resource Center. 1987. “Update: Neem – A New Era in Pest Control Products?” The IPM Practitioner 9(10). U.S. EPA. 1999.
2. Recognition and Management of Pesticide Poisonings. EPA 735-R-98-003. Office of Prevention, Pesticides, and Toxic Substances. Washington, DC.
3. National Coalition Against the Misuse of Pesticides (NCAMP). 2002. “Pesticides and You” NCAMP, Washington D.C. Vol. 21, No.4, 2001
4. EPA Biopesticides Factsheets. Plant Oils. www.epa.gov
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