How to Prevent and Get Rid of Mealybugs, a Common Pest That Can Harm Almost Any Houseplant
Most gardeners are wary of insects when it comes to their outdoor plants, but indoor greenery is just as susceptible to unwanted pests. One of the most common bugs that houseplants encounter is mealybugs, which can damage plants by feeding on sap; this often results in yellowing leaves, stunted growth, and even plant death.
If you've noticed a white, waxy coating growing on your houseplants, then it's possible you have a mealybug infestation. But this doesn't mean your potted greenery is a lost cause, since mealybugs are easy to prevent and get rid of with common gardening supplies.
What Are Mealybugs?
A part of the pseudococcidae family, mealybugs are easily recognized by their white, waxy, cotton-like material. "When they are in mass, you might mistake them for a clump of fuzz on your plant," says Rachel Schnaitman, associate director of horticultural operations at Longwood Gardens. The slow-moving, oval-shaped insects feed on plant juices from houseplants and carry and spread diseases. Adult male mealybugs have wings and two long tail filaments, while females are round and wingless. "As the male insect is rarely seen, you're probably looking at a female mealybug if you do find one on your plant," Schnaitman says.
Why Mealybugs Are Harmful to Plants
Mealybugs can damage your plants in a variety of ways. "They excrete their waste, called honeydew, which is a sticky, clear liquid," says Schnaitman. "This liquid often causes mold, called sooty mold, to grow on the plant—further damaging and reducing plant health." Additionally, the insects feed on plant sap, which can reduce plant health and overall vigor. A large infestation of mealybugs can slow plant growth and cause leaf distortion.
How Mealybug Infestations Form
Mealybugs are often a result of overwatering and over-fertilizing your plants. "They are attracted to plants with soft growth and high nitrogen levels," says Carrie Spoonemore of Jackson & Perkins. Typically, mealybug infestations occur by bringing an infested plant home from a nursery and placing it in close proximity to your other houseplants. "They can live in the roots and spread from plant to plant, feeding off of growth points," Spoonemore says.
How to Prevent Mealybugs
The best way to protect your houseplants from mealybugs is to prevent an infestation before it forms. Start by ensuring that your plants are healthy, and not weak, under-potted, or stressed. "Next, reduce watering and fertilizing and wipe foliage regularly—and always carefully examine all new plant purchases for infestations before bringing them into your home," says Spoonemore. "If you have an infected plant, it is vital to quarantine it to prevent the spread to other plants."
How to Get Rid of Mealybugs
If you've spotted a white, waxy coating on your houseplants and have identified it as a mealybug infestation, there are a handful of ways you can get rid of the pest.
One easy way to get rid of mealybugs is to use a cleaning staple you likely already have on hand: rubbing alcohol. "Soak a cotton ball with no more than 70 percent isopropyl rubbing alcohol and wipe it on the mealybugs on the plant," says Spoonemore. "Be sure to test it on one leaf before applying the alcohol to the whole plant to ensure the alcohol doesn't burn it."
Neem oil is a vegetable oil that's effective at getting rid of mealybugs. "Dilute 2 to 4 tablespoons of neem oil concentrate with 1 gallon of water and add the solution to a spray bottle," Spoonemore says. "Before applying the solution to the entire plant, test out a patch to ensure it will not kill the plant." Once you know it's safe to apply, spray the neem oil solution on the entire plant, including underneath the leaves. Repeat this process after a week or two if the infestation continues.
An effective way to get rid of a variety of houseplant pests, insecticidal soap can also be used to treat mealybugs. "Dilute the insecticidal soap with water. Start with adding 1 teaspoon of soap at a time, and add more depending on the severity of the infestation," says Spoonemore. Pour the solution into a spray bottle and apply it directly to the foliage, paying close attention to the underside of the leaves where mealybugs commonly hide.
There are several types of insects that can naturally kill a mealybug infestation. "These include lace bugs, parasitoid wasps, and a beetle known as the mealybug destroyer," says Spoonemore. "Introducing predatory insects is more commonly used for outdoor infestations or in greenhouses." You can purchase predatory insects from commercial online retailers—but reserve this method for outside plants only.
Alternatively, you can make your own spray to treat mealybugs. To do so, combine a bulb of garlic, a small onion, and 1 teaspoon of cayenne pepper in a blender and blitz into a paste. Next, add 1 quart of water to the paste and allow it to steep for at least an hour. "After steeping, strain the mixture through a cheesecloth and add one tablespoon of liquid dish soap," says Spoonemore. "Add the mixture into a spray bottle and apply to the plant and infestation." This homemade mixture lasts for up to one week in the refrigerator.