Dried coffee grounds, heated until they smoke, can deter flies from your kitchen, according to a hack tested by Ideal Home. The effect lasts for about three hours.
The Coffee Grounds Method
According to Tasting Table, a US-based food media company, you should take dried-out coffee grounds and heat them over a low heat until they start to smoke slightly. Place the heated grounds in a small, heat-safe dish before placing it near open windows or rubbish bins.
The roasting process releases high concentrations of compounds like furans and pyrazines. While many humans love the smell these compounds release, they act as a natural bug deterrent.
Testing the Hack
Lauren Bradbury, writing for Ideal Home, tried the hack herself. She wrote: "After burning coffee grounds from my own morning brew in the oven for 15 minutes, I was left with a smoking pile of coffee that made my house smell like a café."
"And within a few minutes of placing it on my kitchen worktop, the flies that had been buzzing around left through a window I’d left open for them. For the next three hours, my house was a fly-free zone - despite leaving the window open. However, the magic wore off after that, and the flies started to return."
Limitations and Expert Views
James Copley, the CEO of Copley Pest Solutions, expected this to happen. He told Ideal Home that while smoke will deter them, it is not a permanent solution. He adds that the most effective way to banish flies from your home for good is to remove whatever attracted them in the first place.
Emma Grace Crumbley, an entomologist for the pest control company Mosquito Squad, says that there aren't actually any scientific studies supporting the idea that burning coffee grounds can repel insects. Some studies suggest it's actually smoke from the toasting process that flies dislike, because smoke spells danger to them.
