Do Coffee Grounds Keep Mosquitoes Away? The Science Explained
Does smoldering spent coffee keep mosquitoes away? We break down the viral DIY hack, what the science says, and other ways to clear your yard.
Show of hands: who likes mosquitoes? If you raised your hand, I don't know how to help you. If, like me, you're always on the lookout for a new way to get them far away from you and your backyard, you'll want to read this.
There's a lot of buzz (get it?) recently around coffee and its possible mosquito-repelling properties. But where does it all come from? And is there any actual science behind it? Let's take a dive into this unusual method of backyard mosquito control.
How to Repel Mosquitos with Coffee
If you do some digging around the internet, you'll quickly find that the best way to repel mosquitos with coffee is to burn the spent grounds. (I've noticed coffee companies are especially eager to tell you this, so read into that what you will).
Here are the steps:
- After brewing, spread grounds into a thin layer on a sheet of aluminum foil.
- Leave the foil in the sun for a day to allow the grounds to dry out completely. (Make sure it's out of the wind!)
- Scoop a few spoonfuls of dry grounds into a fireproof bowl. You can get one on Amazon, or just make a simple one out of foil.
- Place the bowl near where you'll be spending time, preferably upwind.
- Using a match or lighter, light the grounds in the center of the saucer.
- Allow the grounds to smolder, sit back, and enjoy your mosquito-free outdoor space.
Does This Actually Work?
It's not at all hard to do this routine. The question is, does it do anything? In a word... maybe.
There has been some research to support the use of coffee grounds to repel mosquitoes, but it's a little dubious. According to this study published in 2015, water with a high concentration of coffee in it does deter female mosquitoes from laying eggs. Here's what the study has to say:
"Oviposition responses were extremely low when ovicups holding highly concentrated extract (HCE) of coffee were the only oviposition sites... Larval eclosion occurred at lower rates among eggs that matured in a coffee environment, especially among those that were maintained on HCE-moistened substrates."
In other words, female mosquitoes will actively avoid laying eggs in water containing coffee, and eggs that are laid in coffee are less likely to hatch. That seems promising, doesn't it? It is promising... if you want to cut down on overall mosquito populations. Unfortunately, it won't do anything to drive away the ones that already live in your yard.
If you do want to take a bite out of future mosquito generations, there are much more effective ways to do it than leaving out cups of coffee all over the garden. The best thing you can do is buy a pack of mosquito dunks for less than $10 on Amazon. Mosquito dunks work on a similar but fundamentally different principle to the coffee extract used in the study above. They're made with the bacterium Bacillus thuringiensis israelensis (BTi), which targets mosquito larvae and kills them before they get a chance to take off and buzz in your ear.
To get the most out of your mosquito dunks, use them to make a mosquito bucket of doom.
Should You Burn Coffee Grounds to Repel Mosquitoes?
So what about burning coffee grounds? Does it do anything at all? It might, but the truth is it's going to have just about as much effect as burning anything else. Smoke masks human odors, and it makes the air harder to breathe, so mosquitoes (and pretty much all bugs) steer clear of it. To that end, it's more about the smell you like the most. If you love the smell of burning coffee in the morning, then have at it! Otherwise, maybe stick to the citronella candles.
Other Forms of Mosquito Control
