Mosquito Repelling Plants
As the Zika Virus spreads into North America, there is more and more concern about controlling mosquitoes and preventing bites.
There are many claims regarding mosquito repelling plants, but are they true? Mostly, no. Carefully sifting through all the internet “information”, it takes some doing to nail down actual scientific data, Some of the most extensive studies seem to have been done in Africa. They are highly motivated with high incidents of mosquito borne viruses. None of the data produced, from any study that I found, were from studies of the repellency of the plants themselves, only of the oils, extracts and fragrances released by destroying the foliage.
Did you know there are nearly 3500 species of mosquitoes? They do not all react in the same way to repellents. Extracts from specific plants are effective with specific species. Generally the mosquito species are regional, so look for plant extracts generally used in your area. Mosquito species across the US are probably fairly consistently related, but of course we now know that mosquito types that are likely to spread Zika prefer tropical areas at least from the research so far. So repellents effective with Zika carrying mosquitoes in Africa for example may well be effective in North America.
So, what has found to be true?
There is no plant that when growing in your garden or landscape that will keep mosquitoes away. Any plant that actually produces a mosquito repellent must be crushed to release the repelling oils. Furthermore, many of the plants touted to be mosquito repellent actually are the least effective even when crushed and applied. We are all in general aware of how scent is involved in attracting and repelling, but plants do not emit enough scent to accomplish much even when grown in large numbers. Just having the plant present has little or no affect, the oils must be released.
The best way to actually control mosquitoes in the first place is to prevent larvae. As much as we try to stay away from chemicals, cities everywhere do in fact spray to prevent mosquitoes from laying eggs and larvae from hatching because of the health risk of mosquito born viruses. Unfortunately the chemicals are very effective and natural substances are not.
On a small scale in our own back yards growing basil and peppermint is often suggested to prevent mosquitoes. But although basil and peppermint extracts are toxic to mosquito larvae, just growing the plant does not put the extracts into the water where eggs will hatch.
As for “mosquito plants”, including Citrosa geraniums and Lemongrass, they just don’t work by simply being present. And there is so little citronella in plants that have been developed to produce citronella that effectiveness is minimal and short lived.
What can we do then to naturally repel mosquitoes?
We can of course grow plants that produce the mosquito repelling oils and figure out how to extract and use those oils. Some are more effective than others and with varying methods of extraction and use. Most are only effective for a very short period of time but some for an hour or two as compared to 6 or 8 hours protection with DEET.
Basil, Bee Balm, Catmint, Citronella Grass, Clove, Eucalyptus, Flossflower, Garlic, Lavender, Lemon Balm (Horsemint), Lemon Thyme, Lemon Verbena, Mint, Rosemary, Tea Tree, Vanilla Leaf, Wild Bergamot All these release mosquito repelling oils from the foliage. When working in the garden or in the yard, frequently brush your hand over the plants to release the oils. But more effective is to break or crush a leaf and rub it over your skin. Lemon Thyme is very effective and Lemon Balm has hundred times more citronella in its’ oils than the “Mosquito Plant”.
Basil is a very pungent herb and may have some effective repelling properties strictly from its’ scent without being crushed. Lemon basil and cinnamon basil are most potent but will be more effective if crushed and applied to the skin.
Lavender and Thyme produce strongly scented oils that can mask sweat scents and carbon dioxide that attract mosquitoes to people. This just makes it a bit harder for the mosquito to find you.
DIY Mosquito Repellents
In addition to releasing repelling oils by crushing leaves, they can also be simmered and concentrated into a potpourri or burned to release a repellent smoke.
Crush leaves of the above mentioned plants and rub the oils directly on skin.
Make a repellent spray. Crush leaves and soak in 3 parts vodka to 1 part crushed leaves. Allow to soak for a few weeks, then strain. Store in dark bottles out of sunlight to preserve the shelf life of the essential oils.
Purchased essential oils can be combined with a carrier oil of your choice (olive, almond, grapeseed), and witch hazel. Use 100 drops essential oil, 2 tablespoons of oil and as a preservative 1/2 teaspoon of vodka.
Burning Thyme leaves can provide high protection for well over an hour.
Burning or heating Lemon Eucalyptus can provide moderate protection.
For a Ready to Use natural product, the CDC recommends Repel Lemon Eucalyptus Insect Repellent. Studies suggest complete protection for several hours when applied to the skin. Also natural essential oils from citronella can provide complete protection when applied to the skin.
Any substance applied directly to the skin, even a completely natural substance, can cause skin irritation. Always test just a little!