We Asked an Entomologist If Pennies in Water Could Keep Flies Away—And Her Answer Surprised Us

Flies buzzing around are a common annoyance when the weather turns warm. Many people turn to homemade methods to keep flies at bay, such as hanging a bag of water with pennies. This method is believed to confuse flies due to the reflections caused by the sun, water, and copper pennies – but does it work? 

We spoke with a pest control expert to find out and get additional tips on how to keep flies away.

Do Pennies in Water Actually Keep Flies Away?

The short answer is no, according to entomologist Emma Grace Crumbley.

“There is not enough evidence to suggest that this is an effective preventative method for fly control,” Crumbley says.

If anything, it may even do the opposite by attracting flies to the water.

“Condensation on the bag can attract … flies, and leaks from the bag can create new moisture areas for the flies [to drink],” Crumbley says.

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4 Fly-Repelling Methods Pros Actually Recommend

Use Citronella

Whether you have citronella growing in your garden or in the form of a candle, it’s an effective scent to deter flies and other insects. Citronella is also found in many bug sprays. Keep the plant or the product with the lemony scent nearby in your outdoor spaces, kitchen, or wherever you typically see flies. 

Minimize Trash and Waste

According to Crumbley, the best way to prevent flies is to identify their feeding and breeding source and then remove it.

“Most flies prefer the scents of filth, organic decay, and waste,” Crumbley says. “Remove scents that attract them. Pick up animal waste, clean and seal trash bins, and keep compost sites tidy.”

Use a DEET repellent

Cumbley recommends an EPA-registered fly repellent with DEET to keep flies away, especially for hikes or walks. DEET interferes with flies’ senses and keeps them from landing and biting. DEET repellents can be purchased at most supermarkets or gardening stores and are best used outdoors.

Try Peppermint

Peppermint is another natural repellent to most insects, including flies. You can use peppermint in multiple ways, such as growing a mint plant in your garden or spraying a combined solution of water and peppermint oil around areas with flies.

When using peppermint oil, make sure to spray the water-diluted solution often to keep the scent fresh.

5 Tips for Keeping Flies at Bay

• Remove moisture. Flies thrive in moist environments, so keeping areas dry will take away their breeding sites and lead them to look elsewhere to lay eggs. Avoid leaving containers or areas of standing water, especially under the shade cover. Dump out kiddie pools after use and run water fountains regularly to make the water unappealing to flies.
• Reduce access to food sources. Flies are attracted to various food sources, including traditional food, organic matter, waste, and carrion. Seal up containers that contain trash or food if they’re not in use, and remove other sources as much as possible.
• Install screens. Protect your entry points from flies by installing screens in windows and doors around your home. You may even consider turning your deck or patio into a covered, screened-in porch to enjoy the outdoors without pesky flies buzzing around.
• Run a fan. Flies prefer stagnant, humid environments, so running a fan can maintain the air flow around your home to deter flies indoors. Outdoor fans work well for decks and patio spaces, too.