Got pests? Got coffee grounds? Then you can use coffee grounds to keep those pests away.
Coffee grounds deter pests because they contain chemicals that harm or kill many insects and animals, such as ants, mosquitoes, flies, snails, cats, and deer. These insects and animals stay away from coffee because they know it’s dangerous.
In this post, you’ll find out:
- Why insects and animals stay away from coffee
- A list of pests that coffee grounds deter
- How to use coffee grounds as a pest repellent
- What pest coffee attracts (and how to kill the pest anyway)
How coffee grounds deter pests
Coffee grounds make an eco-friendly and effective pest repellent.
Animals and insects have sensitive noses, which help them stay away from strong smells and things that might harm them. Coffee smells dangerous to many insects and animals, so they stay away from it.
Coffee contains many chemical compounds, but there are two that play a major role in deterring pests:
The caffeine in coffee is what gives people a boost and surge of energy. It’s also why many of us enjoy drinking coffee.
But caffeine is toxic to animals and insects.
If animals or insects take in or are exposed to too much coffee, they could experience higher blood pressure, an irregular heartbeat, muscle spasms and loss of muscle control, shaking, and even seizures.
A caffeine overdose kills insects and animals, and it’s even being used by the Environmental Protection Agency (EPA) to control invasive species under strict controls.
Diterpenes occur naturally in plants as a form of self-protection: Plants use diterpenes to stop animals and insects from eating them.
Diterpenes are chemical compounds that are designed to disrupt an insect’s hormones, so they don’t grow properly. And diterpenes make animals restless, bloated, weak, and can even kill them.
Coffee comes from a plant and has diterpenes in it.
Pests that coffee grounds keep away
Coffee grounds can be used on many insects and animals as a pest deterrent. Below is a list of what coffee grounds repel, and how to use coffee to keep these pests away.
Ants mainly use their sense of smell to find food and as their internal map book to find their way around.
The strong smell of coffee grounds sprinkled in a pot plant or on the ground messes with the ants’ ability to smell, and the coffee smells dangerous to ants so they stay away from it.
Coffee is harmful to beetles.
Spread coffee grounds on the soil around plants that are being destroyed by these pests.
Burning coffee grounds in your home repels bees and stops them from coming into your house.
To keep caterpillars away, dissolve coffee grounds in warm water. It should look like weak tea.
When the mixture has cooled, spray it directly onto plants and soak the ground around the plants with the solution.
The intense smell of coffee grounds can help keep cats away from a yard.
Simply spread coffee grounds around plants and garden borders to discourage cats from coming in and using your yard as a litter box or a place to hunt and fight.
Used coffee grounds can repel fleas and help get rid of an existing infestation.
Next time you give your pet a bath, gently scrub used coffee grounds through the animal’s fur, then rinse well.
Some common flies are attracted to sweet-tasting substances and avoid bitter foods. Coffee grounds are bitter, so they don’t attract these flies. In fact, flies can smell the harmful chemicals in coffee and tend to stay away from it.
You can keep adult mosquitoes away by sprinkling fresh or used coffee grounds around plants and trees, and close to pooled water where mosquitoes are breeding. Alternatively, burn coffee grounds to keep them out of your home.
One study shows that adding coffee grounds to water sources is a great way to control mosquitoes because:
- Mosquitoes avoid laying eggs in water that smells like coffee
- Coffee grounds stop mosquito larvae from developing or surviving
- Mosquito larvae can’t become immune to coffee grounds like they do to commercial repellents on the market, so coffee grounds keep working on mosquitoes
But coffee should be used sparingly and never added to any water that other insects live in or that animals drink because coffee is toxic to them.
Coffee grounds aren’t a reliable way to deter rodents like rats, mice, squirrels, and chipmunks. Rodents are used to digging around in foul-smelling trash and rotten foods, so the smell of coffee doesn’t have much of an effect on them if they’re hungry enough and want to go somewhere.
But, in general, rodents do try to stay away from coffee because they don’t like the gritty texture under their paws and they won’t try to eat coffee grounds because they can smell the grounds are harmful.
Slugs and snails
The mere smell of coffee grounds is enough to keep slugs and snails away because coffee is toxic to them.
Scientists have found that:
- Slugs and snails rarely eat food that’s been sprayed with coffee
- They stay away from growing materials that smell like coffee
- And spraying slugs and snails directly with a strong coffee solution kills them
Caffeine increases the heart rate in slugs and snails, making them weak and killing most of them within 96 hours. And if slugs or snails crawl over soil or growing materials sprayed with a strong coffee solution, about 95% of them die soon after.
Spiders naturally avoid areas that smell like coffee and don’t eat things that have coffee on them because coffee is bad for spiders.
After taking in coffee, spiders struggle to build their webs.
Coffee repels squash bugs that love eating squash, cucumbers, pumpkins, and other harvests.
Add coffee grounds to boiled water and spray the cooled solution onto vegetation or spread coffee grounds around plants to deter squash bugs.
Yellow jackets (wasps)
Burning coffee grounds in your home repels yellow jackets (wasps) and stops them from coming into your house.
How to use coffee grounds to deter pests
Fresh, unused coffee grounds work best to deter pests as these have high caffeine and diterpene concentrations. Used coffee grounds aren’t as potent or effective as fresh coffee grounds, but they can still work.
Here are some easy ways to use coffee grounds based on what pest you’re trying to deter, along with tips on what to avoid:
- Sprinkle coffee grounds on soil to stop cats and others pests from using your garden as a litter box.
- Create a snail and slug barrier by spreading coffee grounds on the earth around any shrubs and plants you want to protect.
- Spread coffee grounds around pet bowls, to stop ants from getting into the animal’s food and water.
- Burn coffee grounds as you would incense in a bowl to deter mosquitoes, yellow jackets (wasps), and bees. Put the bowl of burning coffee on a flat surface and use water to put out the embers when they smell burnt or scorched.
- Dilute coffee grounds in warm water in a spray bottle, then spray the mixture onto plants, focusing on those that attract the most bugs.
- Don’t put wet coffee ground clumps of more than 1/4 cup in a single spot or mold could start growing there.
- As a bonus, coffee grounds are packed with nutrients so they attract many good things like earthworms, red wigglers, and nightcrawler worms. Coffee grounds also feed the soil.
Pests that coffee grounds attract
Coffee grounds attract cockroaches. In fact, many homeowners have trouble with cockroaches nesting in their coffee canisters because cockroaches love the pungent aroma of coffee that repels many other pests.
But you can still use coffee grounds to catch and kill cockroaches. Here’s how:
- Pour some coffee grounds into a paper cup
- Fill a glass jar halfway with water
- Drop the paper cup into the glass jar
- Leave out the trap and wait for cockroaches to drown in the water as they try to get to the coffee grounds