The Common Kitchen Scrap People Use To Repel Wasps (& Does It Actually Work?)

When wasps start hanging around your outdoor space, you're probably trying to think of quick, easy, and inexpensive ways to keep these stinging insects away from you. Online, some gardening and coffee blogs, as well as pest control companies, have suggested that coffee grounds will repel wasps and other insects without having to use harsh chemicals or pesticides. You may be wondering if coffee grounds can really be used as a natural pest control, specifically for wasps, though the answer isn't totally straightforward. There does not seem to be much scientific research about the deterrent effects of coffee on wasps, though there are a few studies about coffee repelling certain species of mosquitoes and some crop pests.

Because of this, there's a possibility that coffee could repel insects, but there's no guarantee that it will actually prevent wasps from buzzing around while you're sitting outside. This control method could be a good experiment to test before resorting to more expensive options. If you'd like to try this method, be prepared that it might not live up to the online hype. 

Some sources online, like Atlas Pet and Wildlife Control and Backyard Boss, claim that you should look into keeping a jar of coffee grounds on your patio because the strong scent of coffee is off-putting to wasps and some other insects, such as mosquitoes, bees, and ants. Others, like Espresso Canada, also mention that the components of the coffee grounds can be harmful to insects. The idea is that by using coffee grounds in your backyard, garden, or patio, the scent will drive off annoying wasps and potentially other pesky insects as well, allowing you to enjoy your space in peace.

To try this method, save your used coffee grounds in small containers, such as jars or a bowl, and place them outside. Try to ensure the coffee is in an area where you've seen the wasps frequently. If you attempt this, be sure to change the coffee grounds often to keep the smell as strong as possible. Certain blogs, like Caffè Borbone, encourage people to burn the scraps as a coffee ground hack to deter wasps, though the effectiveness of this method is just as ambiguous as simply setting some of the grounds in your backyard.

Though there may not be much research about the effects of coffee grounds on wasps, there are a few studies that have examined their use as a repellent and insecticide. In a 2015 study published in Parasites & Vectors, researchers exposed female Aedes albopictus (Asian tiger) mosquitoes as well as their larvae to coffee extracts. The coffee repelled the adult mosquitoes, showing that this kitchen scrap can deter flying insects besides wasps. Additionally, when the pests laid their eggs in water that contained the coffee extract, the larvae didn't develop as quickly.

Another 2022 study published in Plants found that an extract made from used coffee grounds was capable of repelling five different types of insects that feed on the Phaseolus vulgaris bean. Some concentrations of the extract were shown to act as an insecticide. While this research does not focus on wasps, it does show that there is some basis for the claim that coffee grounds can act as a repellent to insects.