Mosquitos have long been a nuisance, and in certain parts of the developing world, they have been the primary culprit spreading serious diseases.
In recent years, North America has been stricken with a new wave of mosquito-borne diseases like the dreaded West Nile and the Zika virus.
This has prompted many people to look for innovative ways to keep mosquitos away from themselves and their property.
Of course, hosing yourself down with DEET and other chemical deterrents aren’t always the preferred option. Especially if you want to entertain guests, or you have small children out and about.
Citronella torches and candles have always been popular options that people have tried to dissuade mosquitos from their deck or patio.
Yet there is some debate about effectiveness of citronella plants as a mosquito repellent. Especially for people who live near forests or wetlands where mosquito density tends to be the highest.
There’s some debate about this method. Do citronella plants repel mosquitoes? If so, how effective is and at what distance? The answer to this question can be a little cloudy, and at first glance, the answer appears to be: No, plants themselves don't repel mosquitoes mosquitos don’t seem to notice the difference between a citronella plant and something like a simple geranium.
In this article, we’ll take a closer look at the citronella plant, how it works and just how effective it might be at deterring mosquitos from your deck or patio.
Which Is The Real Citronella Plant?
Right off the bat, there are variations in this family of plants, obscuring the difference between true citronella and its pretenders.
In fact, the plant that makes citronella oil, that you find in torches and candles is Pelargonium Citrosum.
Taxonomically, it’s closely related to geraniums and bears little relation to a true citronella plant.
Though if you get right up close to it and give it a good smell, it does vaguely resemble the odor of classic citronella.
Where Does Citronella Oil Come From?
The citronella oil that you find in popular outdoor candles and torches is actually extracted from a genus of plants that are closely related to Asian lemongrass.
Taxonomically known as Cymbopogon it is a perennial clumping grass that grows in stands that can get as high as 6-feet tall.
It’s not at all frost hardy, meaning it is limited to tropical and subtropical parts of the world. height of 6 feet.
Do Citronella Plants Really Repel Mosquitoes?
Citronella oil and its aroma have long been touted to deter mosquitos. This belief has been charged by marketing jargon and a wave of media messages that bombard consumers every spring.
Do Citronella plants work against mosquitoes? Closer scientific investigation has produced results that cast some doubt on these claims made on "citronella plant" ("mosquito plant",lemon-scented geranium). On a matter of physical proximity, they are effective in repelling mosquitoes in small areas, you would need to be close enough to it to smell it yourself in order for it to also deter mosquitos.
If you take a moment to do this with the real thing you’ll also find that the odor itself is expressed more when you lightly rub it or brush up against it. Crushing a leaf tends to release the citronella odor the most.
Simply having the citronella plant also known as "mosquito plant" on your deck or patio growing in a container likely will have little effect on repelling mosquitos. it’s the oil extracted from the plant and evaporated into the air that has scientifically been found to help repel mosquitoes. It also requires you to spend a lot of time rubbing, grinding, and outright snuggling with a landscaping feature.
Research published by the United States National Library of Medicine and National Institutes of Health found that: “There are relatively few studies that have been carried out to determine the efficacy of essential oils from citronella as arthropod repellents.
Citronella-based repellents only protect from host-seeking mosquitoes for about two hours although the formulation of the repellent is very important.”
They also note: “The second way to use volatile plant repellents is to continuously evaporate them. Citronella and geraniol candles are widely sold as outdoor repellents, however, field studies against mixed populations of nuisance mosquitoes show reductions in biting around 50%, although they do not provide significant protection against mosquito bites.”
When it comes to preventing the transmission of diseases via insects like mosquitos the United States National Library of Medicine and National Institutes of Health states that “For the time-being travelers to disease-endemic areas should not be recommended to use citronella-based repellents.”
Of course, this research is limited largely to the United States institutions and other organizations limited to North America.
If we turn to Europe we find even less research and fewer recommendations for citronella. Especially when it comes to preventing the transmission of insect-borne diseases.
Part of what reduces its effectiveness is the fact that citronellas main components of citronella-based insect repellents typically include citronella, which contains citronellal, citronellol, geraniol, citral, α pinene, and limonene. These natural oils and components are somewhat volatile.
This means that shortly after application they start to evaporate or oxidize when exposed to the surrounding air. In a relatively short amount of time, it limits their effectiveness to around one hour, perhaps two depending on the prevailing weather conditions.
This ultimately means that to use citronella to deter mosquitos and other insects you will need to frequently reapply, which opens up further questions about safe dosage amounts.
Is Citronella Oil Toxic?
Information published by the National Pesticide Information Centernotes that citronella oil that enters the human body is typically broken down my natural metabolic processes and then removed by the body via urination. However, they also note that many citronella-based insect repellents contain methyleugenol.
Which is “reasonably anticipated to be a human carcinogen” by the United States Department of Health and Human Services. It has caused the development of tumors in mice.
When it comes to the general measure of toxicity the standard measure is to examine the LD 50, in the case of citronella oil the LD 50 on rabbit skin has a value (4700 mg/Kg) and DEET is (4280 mg/Kg). This level of toxicity is generally considered to be safe for both materials.
Do Citronella Candles Actually Repel Mosquitoes?
Research carried out and published by the University of Guelph tested the general effectiveness of citronella candles for repelling or deterring mosquitos as well as other insects. They found citronella candles are ineffective in open areas. in a 5-minute period the test subjects received 6, bites when using quality citronella candles. This is in contrast to 8 mosquito bites when using standard wax candles and 11 bites with no candles at all.
This relatively small data set seems to suggest that citronella candles are marginally better than burning the same number of standard candles and further reduced the total number of bites by half compared to using no candle deterrents at all.
Putting this in context it also means that the average individual will still receive a little more than one bit per minute when burning citronella candles.
To understand the efficacy of this we also need to compare citronella candles to more conventional DEET mosquito repellent.
How Effective Is A DEET Mosquito Repellant?
DEET is an acronym for the chemical name N,N-diethyl-meta-toluamide. It is used by several mosquito repellent manufacturers to deter and repel mosquitos. It’s typically mixed with other components in percentile-based concentrations.
Statistical data on its effectiveness can vary depending on the concentration. One of the more popular insect repellent manufacturers, OFF states, that their “OFF!® FamilyCare Insect Repellent IV contains 7% DEET and can effectively repel mosquitoes for up to 2 hours.” They also state that their “OFF!® Deep Woods® Sportsmen Insect Repellent I contains 98.25% DEET and repels mosquitoes for up to 10 hours.”
They further note that when it’s applied correctly, DEET essentially forms a vapor barrier on your skin’s surface that deters mosquitoes from landing on you.
Chemically it works by interfering with the neurons and receptors in a mosquito’s antennae as well as theoral structures that detect chemicals such as lactic acid and carbon dioxide.
It’s these odors and chemical excretions by humans and other mammals that essentially attract mosquitos to them.
In this way it DEET doesn’t necessarily “Scare” or send mosquitos away, but the scent of it prevents a mosquito from detecting the wearer.
Is it true that the DEET used in most mosquito repellents is toxic?
As far as DEET’s safety and toxicity are concerned the Centers for Disease Control state that “Using insect repellents containing DEET should not be harmful if label directions are followed and the product is used safely. In rare cases, using DEET products may cause skin rashes.
They also warn that you should not allow children under 10 years of age to apply a DEET-based insect repellent themselves. You should not apply to young children’s hands or around their eyes and mouth.
It also should not be applied to open wounds or broken skin. DEET is also toxic if swallowed.
As time goes on DEET gradually starts to lose its effectiveness. This will require reapplication. The higher the percentage concentration of DEET the longer it will generally last.
However, perspiration, water, and even excessively high humidity can potentially accelerate the dissipation process.
Best Ways To Keep Mosquitoes Away From You, Your Home & Garden
The internet is awash with thousands of homespun remedies, each with its own debatable level of effectiveness. There are some who claim that wearing dryer sheets wards off mosquitos.
Others claim to keep mosquitos away by rubbing yourself down with odorous plants, or animal urine.
Most of these options are impractical. However, one method for keeping mosquitos off your deck or patio is to install an outdoor fan.
Mosquitos struggle to fly in a breeze, often choosing to hold onto lower plants and grass. This simple option can help keep them away from your outdoor entertaining space.
Mosquitoes can’t fly against a breeze, so using an outdoor fan can be a really effective way of preventing them from coming near you. Aim the airflow toward the lower half of your body, since mosquitoes tend to fly closer to the ground.
Their are also chemical mosquito control measures used by municipal organizations and professional companies that have been formulated to kill mosquitos in their larval state.
Mosquito granules also work for spot applications around decks, patios, and campsites. Though they do need to be reapplied to maintain effectiveness.
If you have a patio, pergola, or porch area for outdoor entertaining you might also want to consider screening it in.
This will provide you with a physical barrier against all flying insects and doesn’t require applying various chemicals and oils to your skin.
Is It Worth It To Grow Your Own Citronella Plants?
The citronella plants sold in hardware stores and popup garden centers is certainly a visually attractive plant. They also tend to be relatively easy to grow. They are after all a member of the geranium family.
So, if you can grow geraniums, you can grow citronella. There are certainly people who enjoy the faint odor of the plant as well.
Yet when it comes to acting as a mosquito repellent, it’s ultimately going to be ineffective compared to extracted citronella oil from lemongrass derivative plants, and DEET.
If you are truly worried about mosquito-borne illnesses in your region, you are ultimately better off seeking out stronger chemical options.
Lindsey Hyland grew up in Arizona where she attended University of Arizona’s Controlled Environment Agriculture. She has supplemented her formal education by working on various organic farms, including spending a semester abroad in India.
Growing and/or raising just about anything gets her excited. She is especially passionate about environmental justice and low-tech, sustainable ways to better run small-scale farms and homesteads. Lindsey started Urban Organic Yield to discuss gardening tips and tactics.
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