Mealybugs are common pests on houseplants and outdoor plants, resembling white, fuzzy roly-poly or pill bugs. Most often, mealybugs show up on your plant’s leaves or stems, but they can also infest the soil in potted plants or the garden- and that can be a challenging issue to fix.
Mealybugs in soil are usually members of the Rhizoecus genus. Soil mealybugs attack a plant’s root system, weakening the plant and eventually causing death if left untreated. Effective ways to get rid of root mealybugs include drying out the soil, repotting the plant in new soil, diatomaceous earth, warm water, and hydrogen peroxide or neem oil soil drenches. In cases where treatment is ineffective or the infestation is severe, it may be best to dispose of the entire plant.
I’ve dealt with mealybugs a few times on my indoor plants, so I’ve seen firsthand the damage they can cause. Even though they’re slow-moving insects, their strength is in numbers, and soil mealybugs can multiply pretty quickly before you realize they’re there.
In this post, I’m sharing my best tips for identifying and rescuing your plants from soil mealybugs. You’ll also learn when it may be time to simply discard the plant and how to prevent future infestations.
I’ll be going into detail on each treatment option later, but here’s a quick breakdown if you need answers fast:
How to Use
Stop watering for at least 7 days. Do not use on plants that cannot tolerate dry soil.
Remove all old soil- discard in trash. Rinse roots well. Replant in a clean pot with fresh soil.
Diatomaceous earth (DE)
Sprinkle DE around affected plants and work into the soil. Mix DE in soil when repotting.
Heat water to 100-120 degrees F (40-50 degree C). Submerge root ball for 10 to 20 minutes.
Neem oil drench
Mix 1 T of neem oil, 1 t insecticidal soap and 4 cups water. Pour over soil to soak.
Hydrogen peroxide drench
Mix 3% hydrogen peroxide with water in a 1:5 ratio. Apply to plant as a soil drench.
Throw the plant away
Take any healthy cuttings possible. Bag remaining plant material and burn it or place in the trash.
Let’s get started!
What Are Mealybugs?
Mealybugs are a type of pest found on plants in nurseries and greenhouses that cause damage by sucking sap, according to North Carolina State Extension. These insects are very small and oval. Males have wings and long tails, and both males and females are covered with white protective wax.
Mealybugs include several subgroups:
- Rhizoecus (root mealybugs)
Mealybugs are slow-moving insects that prefer to remain hidden. I’ve discovered them on my houseplants before. Since their white bodies contrast dramatically with green leaves, I’ve always found them pretty easy to see and deal with early on:
But that’s not the case with mealybugs in soil.
For one thing, root mealybugs are tiny- only about 1/16 of an inch in length. That’s opposed to common leaf mealybugs that are about 1/5 of an inch long.
Also, you can’t see them when they’ve burrowed below the soil line or into plant roots, so they can go undetected until you start noticing problems with your plant’s health. At that point, they may be so well-established that they can be difficult to get rid of.
How to Spot a Soil Mealybug Infestation
Female mealybugs can lay up to 600 eggs at a time, and within 6-10 weeks, this new generation matures and lays more eggs of their own. So it’s not hard to see why a mealybug problem can quickly grow.
According to the University of Wisconsin Extension, symptoms of a soil mealybug infestation include:
- Stunted growth
- Yellowing leaves
- Leaf drop
- A sticky substance on stems or leaves, called honeydew. This honeydew leads to mold growth which appears as blackened leaves and stems.
In my experience, root mealybugs are most common in potted plants. If you suspect soil mealybugs, flip the pot over and look at the drainage holes- cottony white masses are a strong sign of infestation. You can also take the plant out of the pot to inspect the roots and inner pot walls. Again, look for the telltale fluffy white masses.
This video from The Succulent Greenhouse shows what an infestation of root mealybugs looks like:
It’s less common, but if the plant in question is in the outside garden, gently dig around the plant base to loosen the soil for inspection. It may be harder to find out for certain that you have soil mealybugs without digging up the entire plant. So if you have other confirmatory signs, I recommend proceeding to treatment strategies and not digging the plant up unless needed.
7 Ways to Treat Mealybugs in Soil
After confirming soil mealybugs as best you can, it’s time to treat your plant’s soil and roots for mealybugs.
For potted plants, the first order of business is to isolate the affected plant to prevent the spread of mealybugs and eggs. Take it into another room if possible.
After that, try one or more of these strategies for how to get rid of mealybugs in soil and save your plants:
- Allow the soil to dry out
- Repot the plant in fresh soil
- Mix diatomaceous earth into the soil
- Warm water
- Neem oil drench
- Diluted hydrogen peroxide
- Throw the plant out if treatment is unsuccessful
1. Allow the Soil to Dry Out
Mealybugs love moisture and higher nitrogen in soil, which is often the case for potted plants that get fertilized regularly.
The first method for how to get rid of mealybugs in soil is to stop watering for at least a week. This allows the soil (and hopefully the mealybugs) to dry out.
But keep in mind that this method will only work if the infested plant tolerates dry soil. Fruiting plants and ornamentals like fittonia (nerve plant), peace lily and some ferns need consistent moisture. With these plants, I would try a different strategy to control soil mealybugs.
2. Repot the Plant in Fresh Soil
Spread out a large piece of newspaper or brown paper, and un-pot the affected plant, brushing away as much of the old soil as possible. Let the old soil fall onto the paper and dispose of it in the trash- do not put it in the compost.
Next, rinse the roots under running water to wash away hidden mealybugs eggs in soil pockets. Then repot the plant in a new pot with fresh soil.
Throw out any porous pots, like terra cotta or cement, and thoroughly disinfect non-porous ones, like plastic or glazed ceramic. The University of Minnesota Extension recommends a general-purpose cleaner with 0.1% alkyl dimethyl benzyl ammonium saccharinate (brand name Lysol) or a 10% bleach solution to disinfect pots before use or after an infected plant is identified.
3. Mix Diatomaceous Earth Into Soil
Diatomaceous earth (DE) is an organic, food-safe way to combat mealybugs and other insects. DE is made up of the powdered remains of fossilized animals. The powder crystals have sharp edges that cut the mealybugs’ protective exoskeleton (waxy covering), leading to dehydration and death.
Sprinkle DE around the base of the infested plant and work the powder into the soil. In individual pots or planters, mix DE into fresh potting soil when repotting infested plants.
I don’t recommend DE as a leaf treatment for mealybugs- instead, stick with wiping them away with alcohol. My reason here is that DE is harmful to many insects’ exoskeletons, including garden friends like bees. So use diatomaceous earth carefully and in the soil only.
Also, be careful when working with DE- the fine powder is a respiratory irritant, so make sure to wear a dust mask and don’t use it on a windy day.
4. Warm Water
Mealybugs are sensitive to temperature, and this next method capitalizes on that.
Heat up water to between 100 to 120 degrees Fahrenheit (40 to 50 degrees Celsius). The water should be quite a bit warmer than usual plant water but still feel comfortable to your skin. Then submerge the root ball for 10 to 20 minutes.
I don’t recommend this method for plants that have low heat tolerance, like brassicas and leafy greens. The warm water could be too great of a shock to the plant, and it may cause more harm than good.
5. Neem Oil Soil Drench
I like to keep neem oil on hand for lots of garden uses- it’s an effective and organic insecticide that works against many pests and plant diseases. Neem oil has a strong scent and chemical compounds that interfere with an organism’s reproduction and growth.
Dilute 1 tablespoon of concentrated neem oil and 1 teaspoon of insecticidal soap in 4 cups of water to make an emulsified solution. You could also use a ready-to-use neem oil spray. In either case, use the neem oil to thoroughly saturate the soil, repeating the treatment weekly until the mealybugs are eradicated.
Test the solution on a single leaf first to check for any wilting or damage after 2 hours which indicates the need for more dilution. Neem oil is safe for ornamentals as well as vegetable and fruit plants.
6. Diluted Hydrogen Peroxide
Diluted hydrogen peroxide is great for plants in many ways, and it can be an effective way to kill mealybug eggs in soil and adult insects. But you’ll have to use a much more concentrated hydrogen peroxide solution for pest treatment than you would for routine usage, and I would use it as a last resort if the other treatments failed.
Here’s what to do. Make a 1:5 dilution of 3% hydrogen peroxide and water. For example, add 1/2 cup of 3% hydrogen peroxide to 2.5 cups of water. Mix thoroughly, and use the solution to water the infected plant, giving enough so that excess runs through the pot’s drainage holes. Repeat the treatment weekly if needed.
7. Throw the Plant Out
If caught early, soil mealybug infestations are usually treatable, even though it may take two or more treatments. However, if the plant has too much damage or a serious infestation that doesn’t respond to multiple treatments, the best option may be to throw the plant away.
David Cohen, CEO of the popular U.K. flower-delivery service Flower Station, says these are signs that it’s time to start over with a fresh plant:
- “Large clusters of mealybugs on the plant, with no visible signs of control.
- Severe leaf drops or wilting indicate that the plant cannot recover from the infestation.
- The presence of other pests or diseases in addition to the mealybugs.”
If there is any healthy sections of stem, take cuttings with a clean scissors/pruners for propagating a new plant.
Then place the remaining parts of the plant in a plastic bag and tie it off. Put it in the trash or burn the plant if possible to prevent spreading mealybugs to any other plants. Clean and disinfect non-porous pots (throw porous ones away) and tools used with the affected plant to prevent spread.
How to Prevent Mealybugs in Soil
Mealybugs in soil can be a tough problem to fully address, so preventing an infestation is really the best strategy.
Whenever I’ve found mealybugs on my plants, I always think the same thing- “Where did these even come from??” According to Richa Kedia, garden expert and founder of Simplify Plants, there are a few ways that these little pests can make their way into your home or outdoor plants.
“Mealybugs can be introduced to indoor plants through infested houseplants or infested soil used to pot new plants. They are known to hide in the crevices of pots, so it is important to inspect new plants carefully before bringing them indoors.”
I’ve come to the conclusion that this is how mealybugs have found their way into my home before. So even if you’re buying from a reputable plant seller, take the time to carefully look over every plant before you buy it or as soon as it arrives if you’re buying online.
But that’s the not only way these little pests can get around. Richa continues, “Mealybugs can also spread through contact with infested gardening tools or by pets or people brushing up against infested plants and then carrying the bugs to other plants.”
So vigilance pays off. Be on the lookout for white, cottony masses and egg sacs. Any signs of leaf yellowing or falling leaves calls for immediate intervention, and only use fresh or pasteurized potting soil for planting (instructions from Penn State Extension here). Other mealybug-prevention tips are to regularly clean and disinfect garden tools, avoid overwatering, and ensure proper drainage.
Frequently Asked Questions about Mealybugs in Soil
It’s disheartening to see our beloved plants suffering from pests, and once mealybugs take up residence in the soil, it can be hard to get rid of them completely. But I can tell you from experience that it’s worth trying, and I hope you’ve seen through this post that you’ve got several ways you can fight back.
I’d love to hear from you! Do you have any other questions about dealing with mealybugs in soil, or have you found any other effective treatments? There’s no better way to learn than from each other, so please feel free to share your thoughts in the comments!