Herbs vs bugs: scents to discourage flies, fleas and other bothersome insects.
The castles of medieval and Renaissance Europe must have been rich in sights, sounds and smells. And after great feasts, imagine the inhabitants tossing bones and other scraps for the dogs on the floor, and the resulting heaps that would accumulate. This may have been a prime reason to own at least two castles so that when "the middens became stinking," the royalty could move on, and the floors could finally be swept out. Just imagine the populations of fleas, ticks and lice evicted along with the detritus! The practice of strewing herbs on the floor to repel vermin and freshen the air between cleanings dates back at least to this era. Leaves of sweet flag, flowers of lavender, and leafy stems of pennyroyal were among the herbs commonly used for this propose.
These days, we have higher standards of sanitation, as well as more effective ways of controlling populations of insect pests. Herbs still can play a part, though, particularly as we search for "natural" solutions from the garden. Countless plants have been used throughout the ages, and plenty have potential as insect repellents.
Insects and scents
Insects as well as other arthropods have an extremely acute sensitivity to odors. For example, tiny amounts of chemicals called pheromones produced by an insect can elicit sexual and other behavioral responses from others of its species. Insects are likewise capable of detecting chemical scents from plants and other animals.
Insects and plants evolved together, and complex interactions have developed between them. Just as many plants can use odors to attract pollinators, they also can produce scents to ward off insects that might eat them. Paradoxically, certain substances that act as insect attractants at low concentrations will repel the same insects at higher concentrations.
The principal component of most leading mosquito and tick repellents sold today is N,N-diethyl-meta-toluamide (DEET). An effective repellent of biting flies, mosquitoes, ticks and chiggers, DEET should not be ingested, inhaled or used in contact with skin. DEET has been shown to be toxic to humans and domestic animals, and reactions can be severe.
Turning away from the laboratory to the plant world for alternatives gives us few definitive answers; much is still uncharted territory. Volumes of anecdotal evidence and historical accounts exist on the repellent properties of many herbs, but few well-designed scientific experiments have been performed to test these claims.
Please remember that herbs carry their own set of dangers and warnings. "Natural" does not mean "harmless." Herbal preparations should not be consumed or sprayed directly on skin unless they're known to be safe. If applied to clothes instead of bodies, the repellency lasts longer anyway.
I have devised an herbal formula designed to repel mosquitoes, ticks, flies and fleas (see above). The formula is based on personal experience and a review of the scientific literature on insect repellency; its effectiveness has not been extensively tested.
Let's look at these herbs and other possibilities from the garden, and how we might use them against pests.
Mosquitoes are the most thoroughly studied insects in the search for repellents, because these bloodsuckers transmit numerous diseases, including malaria and yellow fever. Citronella (Cymbopogon nardus), juniper and several species of basil have been shown to be effective against mosquitoes. Rose geranium, rosemary and several species of cedar all have shown promise in preliminary testing.
The oil of citronella, a fragrant grass of southern Asia, has long been used as an insect repellent and often is sold in candles that are burned on the patio in hopes of driving away mosquitoes in the evening. I use citronella candles myself, although I also question how effective they are. A more effective way to use the repellency of citronella is to apply the oil to skin or clothing.
Basils (Ocimum spp.) can be used as mosquito repellents by either crushing the leaves or applying the oil.
Tansy (Tanacetum vulgare) is another traditional insect-repelling herb; growing it near the doorway of a home to discourage flies from entering is an old custom. If you can find its essential oil, by all means add it to my herbal insect repellent recipe.
An extract of sweet flag (Acorus calamus), especially in combination with an extract of turmeric (Curcuma longa) or pine (Pinus sp.), has been effective against yellow-fever mosquitoes. Many other plants have shown promise against mosquitoes, and among them are yarrow (Achillea millfolium), sweet Annie (Artemisia annua), hyssop (Hyssopus officinalis), German chamomile (Matricaria recutita), bog myrtle (Myrica gale), lantana, marsh tea (Ledum palustre), sassafras and sandalwood.
The ingredients of my herbal formula that might shoo off the common housefly are palmarosa, citronella, juniper and rose geranium.
Other reported fly repellents include the oil of roots of sweet flag, extracts of the twigs of Kenyan myrrh (Commiphora boiviniana), and extracts of the roots of Mexican yellow chapote (Sargentia greggii). Other possibilities include bog myrtle, German chamomile, sandalwood, tomato and vetiver (Chrysopogon zizaniodes).
The oils of lemon and pine are included in the recipe in hopes that they'll keep fleas from mistaking me for a dog. For use in flea pillows and bedding for your pets, I recommend the dried leaves of pennyroyal, fleabane mad California laurel, mixed together with these two oils.
Oh, how l wish that I had a safe repellent of the deer tick, which carries Lyme disease, or a good repellent for the wood tick and the American dog tick, both of which carry Rocky Mountain spotted fever.
Opopanax or bisabol myrrh (Commiphora erythraea) is the subject of the only good scientific tests on natural tick repellency that I can find. Some other herbs indicated in literature as having tick-repellent qualities include rose geranium, rosemary and California laurel.
If your grandma put bay leaves in her flour canisters, it was because of this herb's long reputation as an insect repellent. Today, the effectiveness of bay (Laurus nobilis) in repelling cockroaches is well documented. Simply place fresh or dried bay leaves in and around cupboards, especially where they will be brushed and crushed in normal kitchen activity. Other plants shown to be repellent to cockroaches include Osage orange (Maclura pomifera), Japanese peppermint (Mentha canadensis), Scotch spearmint (M. gracilis) and vetiver.
HERBAL INSECT REPELLENT
This pleasantly scented liquid is de, signed to repel mosquitoes, flies, fleas and ticks. Experiment with the essential oils it contains to determine the most effective formula against the bothersome insects in your area, or adjust the amounts to let a particular favorite scent emerge in the finished product. This is safe for use on skin or clothing. Use a small amount on exposed skin, dab it on clothing, or carry it along with you in convenient pocket-sized plastic bottles on outdoor trips. For external use only.
2 1/2 teaspoons total of the following essential oils in equal parts or in any combination: basil, juniper, palmarosa, citronella, rose geranium, rosemary, myrrh, cedarwood, pine and lemon (1) cup 190-proof grain alcohol, available in liquor stores (1) Stir oils into grain alcohol. (2) Pour solution into small bottles with tight-fitting caps. NOTE: To make more or less of the insect repellent, use a quantit of essential oil equal to 5 percent of the volume of the finished product.
SOURCES FOR ESSENTIAL OILS
(division of Frontier
Natural Products Co-op)
5398 31st Ave.
Urbana, IA 52345
2138 Humboldt St.
Bellingham, WA 98225
ESSENTIAL OIL CO,
8225 S.E. Seventh Ave,
Portland, OR 97202
120 N. Seneca Road
Eugene, OR 97402
MAJESTIC MOUNTAIN SAGE
2490 S. 1350 West
Nibley, UT 84321
MOUNTAIN ROSE HERBS
P.O. Box 50220
Eugene, OR 97405
1030 Calle Recodo
San Clemente, CA 92673
18 Gateway Commerce
Center Drive E, Door PD1
Edwardsville, IL 62025
11253 Trade Center Drive
Rancho Cordova, CA 95742
Pesky flies offer a fascinating, albeit odious, view of the insect world.
This article, in a longer form, was originally printed in Our sister publiccation. The Herb Companion.
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|Author:||Tucker, Arthur O.|
|Date:||May 1, 2012|
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