For many people, enjoying the great outdoors is one of their favorite pastimes. However, that enjoyment can be tempered by the appearance of some unwanted guests: flies.

To combat these pests, folks turn to bug sprays and insect repellents. DEET, around since the 1940s, is one of the most popular and proven effective repellents, but it is a synthetic chemical.

In recent years commercial products promising natural fly deterrence gained popularity, as did homemade fly spray recipes. Type “how to get rid of flies” into a search engine and a host of formulations will pour out, all promising fly control. Look closer, though, and you’ll see little scientific evidence those remedies work at pest control. That’s slowly changing as scientists begin to look at these folkloric concoctions — and discover which ones work.

So, which natural fly deterrents are scientifically proven to keep flies at bay? You might be surprised.

Historic Uses of Plants as Fly Repellents

It’s unquestioned that at least some plants have insect repellent qualities. It stands to reason: Plants don’t want insects gnawing on them, any more than we do. So as they evolved, plants developed natural bug repellent properties. Many plants release a vapor when eaten, for example. Ancient people didn’t know that, but they did know having plants around and burning their leaves would lessen the bother.

Some are more effective than others, but little data has been collected on the topic.

Moghul painting illustrating a man burning neem leaves near a river where biting insects would be present (© Dr. Sarah Moore, co-author “Plant-Based Insect Repellents.”)

Mostly Harmless, Largely Untested

The fact that plant-based fly deterrents are natural allows them to fly under the regulatory radar. Because they are natural and not seen as a serious safety risk by the Environmental Protection Agency, they are not registered with or evaluated by the EPA for effectiveness. Without science to prove how they repel flies and other insects, these natural fly repellent sprays are more a matter of personal anecdotes and folklore.

This is particularly true of botanical repellents — products labeled “natural” because they include plant-based fly spray chemicals. However, according to Consumer Reports, which conducts its own independent product tests, in repeated testing, most of these natural ways don’t work well.

“Recently, commercial repellent products containing plant-based ingredients have gained increasing popularity among consumers, as these are commonly perceived as ‘safe’ in comparison to long-established synthetic repellents although this is sometimes a misconception,” says a 2011 study “Plant-Based Insect Repellents” published in Malaria Journal. Much more standardized testing is needed, the study said, “to better evaluate repellent compounds and develop new products that offer high repellency as well as good consumer safety.

Comparing Natural Fly Spray Solutions

Here’s a breakdown of some scientifically proven solutions for your spray bottle, along with a sample of common folklore solutions, supported mostly by anecdotes.

Products With at Least Some Scientific Backing: 

  • Oil of lemon eucalyptus (OLE): Consumer Reports gave OLE products their top ranking. In its tests — which involve having human test subjects stick their arms for an hour in a container of 200 mosquitoes — OLE provided a repellent effect for as much as six hours. It’s important not to confuse “oil of lemon eucalyptus” with the similarly named “lemon oil eucalyptus.” The first is certified effective by the EPA, the second is manufactured in a different way, and is less effective.
  • Lemongrass oil: According to “The Repellency of Lemongrass Oil Against Stable Flies, Tested Using Video Tracking” published by the National Center for Biotechnology Information in 2013, stable flies spent significantly more time in the study’s untreated zone than in the treated zone. As a result, the study found, “These results suggest that lemongrass oil could be used as an effective repellent against stable flies.”
  • Catnip: A 2009 study by the University of Nebraska-Lincoln found that catnip essential oil was quite effective as a natural repellent, with an average repellency rate of 96 percent against stable flies and 79 percent against houseflies. The study further stated, “In comparison with other U.S. Environmental Protection Agency-approved mosquito repellents (DEET, picaridin and p-menthane-3,8-diol), catnip oil can be considered as a relatively safe repellent, which may cause minor skin irritation.”
  • Coconut oil: While this product has garnered a lot of attention for its potential health benefits, it also attracted some scientific interest in the field of natural fly deterrents. Specifically, in a study by the USDA’s Agricultural Research Service and published in Scientific Reports in 2018, compounds derived from coconut oil proved to be a better repellent than DEET. That compound is specific coconut fatty acids–not coconut oil itself. As stated in the report by entomologist Junwei Zhu, coconut oil itself is not a repellent. When tested against stable flies, the coconut oil compound was more than 95 percent effective, while DEET was only 50 percent effective.
  • Citronella: A very popular natural repellent against flies, mosquitoes and other flying insects, this plant-based oil is often added to numerous products to help deter flies. Its effectiveness, though, is not a sure thing. According to a 2011 study published in the Malaria Journal, “citronella-based repellents only protect from host-seeking mosquitoes for about two hours although formulation of the repellent is very important.” Depending on other additives in the repellent, citronella can be more effective. Citronella candles also are extremely popular, but “field studies against mixed populations of nuisance mosquitoes show reductions in biting around 50 percent, although they do not provide significant protection against mosquito bites,” the report said. Citronella oil products can be applied directly to the skin as a bug repellent, as well.

So Far, Mostly Anecdotal Support

  • Witch hazel and apple cider vinegar: A popular home remedy, a mixture of witch hazel and apple cider vinegar along with a touch of eucalyptus oil will ward off flies because they don’t like the smell.
  • Cloves: Apparently, flies are not fond of the smell of cloves, so placing a mesh or cheesecloth pouch of crushed cloves in areas you want to deter flies can be effective.
  • Lavender oil, tea tree oil, rosemary oil, peppermint oil, essential oil blends. All have shown some promise in initial tests.

Natural, Yes. Eco-Friendly and Harmless? Maybe Not

Even if a plant-based substance provides promise, that doesn’t mean it will lead to a product friendly to humans and the planet. As the “Plat-Based Insect Repellent” study points out, “Some natural repellents are safer than others, and it cannot be assumed that natural equates to safe.”

It’s not necessarily true that extracting repellents from plants is better for the Earth, either, the study says. “While plant volatiles are naturally derived, distillation requires biomass energy, extraction commonly uses organic solvents that must be disposed of carefully, growing the plants uses agrichemicals, such as fertilizers and pesticides (unless sourced from a sustainable and organic source).”

Cleanliness Leads to Flylessness

Though natural fly repellents’ day has not yet fully arrived, there’s still plenty you can do to reduce the insect’s presence in your life.

One of the best ways to keep flies away is to maintain a lawn and garden that flies find unattractive. If you have a composting pile, you’ll want to place it in a corner of the yard away from the house. Flies are attracted to decaying organic matter, so they will love your compost pile. If the pile includes fruit, it’s almost guaranteed to attract fruit flies.

Grass clippings can serve as valuable nutrients for your lawn, but make sure they are spread evenly to promote quick breakdown. If left to clump and even mildew, they will attract flies. The same is true for piles of dead leaves.

In addition, there are a number of herbs and plants credited with keeping flies away, so you can add these to your garden or grow in pots and move about as needed. These include Mexican marigolds, mint, rosemary, lavender, yarrow and pitcher plants.

You also should clean out all areas that collect water, as these attract not only flies but also mosquitoes. Make sure animal waste is removed and disposed of properly as this, too, can create a fly problem. Trash cans should be well-maintained and closed at all times.

Some Natural Solutions Attract Flies

Instead of repelling flies, some repellent recipes attract them.

  • Fly traps. Take a Mason jar or other small glass jar or bottle and add about 1/4 cup of sugar, 3 inches of apple cider vinegar, 1/2 cup of water, and a drop of dish soap. Secure a piece of plastic wrap over the top and poke holes in it. Flies — particularly fruit flies — will drown in your homemade fly trap. Vinegar is overrated as a weed-killer, but as a fly-trapper, it’s superb.
  • Flypaper. Modern versions are not toxic, they’re just sticky. Flypaper has dropped in popularity in recent years, probably due to having dead fly bodies suspended in living spaces.

The Final Word

While there is a case to be made for natural fly deterrents, science has yet to prove that all-natural remedies are anywhere close to being as effective as a fly swatter. The great majority of natural solutions are unscientific, anecdotal remedies passed down from generation to generation or, in today’s Internet age, passed along on social media. The true test of those remedies lies in trial and error on an individual basis unless and until scientists set their sights and studies on them.

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