Don't Throw Away Your Coffee Grounds: Use Them To Get Rid Of This Garden Menace

Believe it or not, getting rid of mealybugs (Pseudococcidae) is among the many unexpected uses for coffee grounds in your garden. The reason coffee grounds are effective at controlling these pesky scale bugs is the combination of strong smell, caffeine, and alkaloids. In fact, there's evidence that even the caffeine remaining in spent coffee can kill mealybugs. Using coffee grounds to repel mealybugs is also incredibly easy and can be done in a couple different ways. Coffee grounds can also add nutrients to the soil. Additionally, since the grounds are non-toxic, as opposed to using chemical pesticides, will protect bees, butterflies, and other garden pollinators.

If you've seen these pale, soft-bodied critters clustered along a plant's stem or a leaf's petiole and wondered if you should do something about them, the answer is yes. This is because mealybugs are quite the menace, especially when growing citrus and broadleaf ornamental plants. As they feed on your plant, they weaken it, causing stunted growth yellowing leaves and worse. The invasive pasture mealybug has been spotted in Texas, and can wipe out entire yards, fields, or grasslands. On the whole, mealybugs are notoriously difficult to get rid of once established and can spread rapidly if plants aren't quarantined in time. So, if you happen to see mealybugs on your plants or notice the tell-tale signs of their presence, such as their puffy, cotton-looking excretions, then don't throw away your coffee grounds: Instead, use them to help get rid of mealybugs.

There are a couple of easy ways to use coffee grounds to repel mealybugs in your garden or on potted plants. You can use either one, or employ them simultaneously for even more protection. The first method involves making a liquid spray — essentially a very weak coffee. Avoid using fresh, full-strength coffee, as it is more acidic and caffeinated, which can hurt plants. To use this method, pour a tablespoon or so of spent coffee grounds into a spray bottle filled with water. After allowing it to sit overnight, the mixture is ready to use. Apply a fine mist to plant foliage and stems. Reapply every week or so (more frequently if you see an infestation) and following every rain.

The other simple method is to lightly scatter used, dried coffee grounds across the soil in your garden. This helps prevent mealybugs from burrowing into the soil and targeting the roots of the plants. Doing so will have the additional benefits of enriching the soil with nutrients, as well as repelling ants and other pests. However, don't overdo it. If you lay a solid layer of coffee grounds over the soil it can form a water-blocking concretion. It's also worth pointing out that there are some plants you shouldn't fertilize with coffee, as it is relatively high in nitrogen, so double-check that this is the right pest repellent for your plants before you apply it. Inspect your plants daily and wipe away any mealybug excretions or carcasses. Ideally, you'll see improvements in 2 or 3 weeks.