Root mealybugs. Some species, like the one above, lack eyes.

You thought that no houseplant pest could be worse than the common mealybug? That just goes to show that you haven’t yet had to deal with its underground cousin, the root mealybug (Rhizoecus spp.), also called soil mealybug. Though the average one is only about 1/16th of an inch (1.5 mm) long, that is, about one-third the size of a mature common mealybug, it packs quite a punch… and to make things worse, it lives underground, out of sight. In other words, it is even harder to spot than the common mealybug that lives on stems and leaves, because how many times a year do you take your plant out of its pot to examine its roots?

Favorite Plants

Root mealybugs can be found on almost any houseplant (pelargoniums, ferns, fuchsias, etc.), but they seem to be especially fond of African violets (Saintpaulia) and succulents, including cacti.

These insects are essentially houseplant pests in most areas and I’m treating them as such here. However, in tropical and subtropical climates, they can attack outdoor plants as well.

Life Cycle

Root mealybugs are active all year round, but their life cycle speeds up in summer (about 1 month from egg to mature adult) and slows down in winter (up to 4 months from egg to mature adult).

Root mealybugs feed by piercing a tiny hole in the plant’s root with their buccal parts and suck up the sap that flows out.  This weakens the plant and can eventually kill it.

Females deposit an egg sac covered in white powder here and there in the soil, often towards the outside of the rootball. The eggs hatch into crawlers, tiny nymphs essentially  identical to the mother except for their smaller size. They are the most mobile stage and can easily spread to other plants. Crawlers seem especially active when you water plants and it is often when you are watering that they are washed out of one pot and move to neighboring plants. Crawlers also wander about on their own, mostly at night.

Unlike scale insects (another close cousin) that settle down when they reach adulthood, never to move again, root mealybugs remain mobile all their life. Root mealybugs are more likely to infest plants that share a tray than plants grown in individual saucers, as a saucer, though small, still remains somewhat of a barrier to insect movement.

Recognizing Them

Root mealybugs are often said to resemble a grain of rice and, as with all mealybugs, are covered with a waxy white cottony substance, giving them the “mealy” appearance their common name implies. Some species have no eyes (you may know those under the name blind mealybugs) and in fact, it’s hard to tell the front from the back!

Here you see the results of a root mealybug infestation: a few adults, lots of dead white skin, egg sacs and “mealybug powder”.

At the beginning of a root mealybug infestation, there is no visible symptom unless you examine the soil. When the number of insects increases, the plant starts to show symptoms of general decline: nothing too specific, but it stops growing, becomes pale, stops blooming or loses leaves. Often plant owners figure the plant needs more light or fertilizer or is suffering from rot, but any improvements made to growing conditions have no effect. Only in the most advanced cases can you actually see root mealies above the soil line, as they sometimes congregate at the very base of the plant when the root system is completely infested.

Sometimes, when the root system is severely infested,  you can see tiny bits “white fluff” in the saucer when you water, usually egg sacs or remains of egg sacs. That’s a sure sign an infestation is in progress.

Even when you unpot an infected plant to examine its root system, mealybugs are not that easy to spot, especially when the potting mix contains perlite (particles of expanded white rock), because the two are easily confused. However, if you look carefully, its cottony appearance and more symmetrical shape help the mealybug to stand out from irregular particle of perlite. Or squeeze the suspicious particle between your thumb and forefinger: it goes “crunch”, you’ll know it was perlite, if it goes “squish”… well, it used to be a mealybug!

Besides root mealies themselves, you’ll discover they are rather messy insects and leave clusters of pure white cottony wax here and there, white egg sacs and also powdery white wax on roots. Often you’ll see signs of their presence rather than the pests themselves.

White markings with a bluish tinge to them show this pot is hosting soil mealybugs.

The pot will have traces of them as well, in the form of small bluish-white spots on the inner wall. The marks on the pots, in fact, are often what give their presence away.


First, isolate the infested plant… and check immediately any other plant nearby. These mealybugs do get around!

Next, think seriously about tossing the plant: that remains the easiest and most effective treatment.

You can save your plant by taking a cutting. Here a cactus cutting is being allowed to callus over before being potted up.

The second easiest treatment? Take cuttings from the aerial part of the plant (root mealybugs live strictly underground, so plant stems are therefore free of them)… then throw away the infested mother plant.

You can theoretically kill root mealies by slowly pouring an insecticide solution into the soil until saturation, but personally I’d be concerned that a few would survive and start a new infestation. After all, the soil will still be full of little white specks. How will you know the pest isn’t still alive and proliferating? Or that a few egg sacs haven’t survived?

Another possibility is to unpot the plant, thoroughly rinsing the roots to remove all soil. While you’re at it, prune off any dead roots. Now soak the roots that remain in a diluted solution of the insecticide of your choice for 15 minutes. Afterwards, repot in fresh potting soil and a clean pot. Consider adding diatomaceous earth, a biological insecticide, to the potting soil at a rate of about 1 tablespoon per liter of mix as a way to keeping them from coming back.

Under laboratory conditions, scientists have controlled root mealies by soaking the roots in hot water (120?F/49°C) for 10 minutes, but it’s difficult to maintain a steady temperature under home conditions. If the temperature drops too much, some scale insects will survive; if it becomes too hot, that can kill the roots.


Make sure you inspect the root ball before you buy a plant.

Before buying a plant (especially a succulent or cacti, as there seem to be a lot of root mealybug-infested succulents on the market these days!), ask the clerk to remove the plant from its pot so that you can examine the plant’s rootball… and the inside of its pot.

When you get home, put the new plant in quarantine for at least two months and even then, remove it from its pot and carefully examine its roots before placing it among your other houseplants.

True enough, root mealybugs can be sneaky, but at least you now know what to look for… forewarned is forearmed!

15 comments on “Root Mealybugs: Death From Below

  1. Terra T.

    I just discovered root mealy bugs in an overcrowded pot of Haworthia truncata I’ve had for maybe 15 years! The infestation isn’t too bad and I’ve taken the kids out of the pot and pruned off the dead roots and removed all the mealybugs I’ve seen with soapy Q-tips. In the past I used to water my succulents with water that had a little bit of dish soap in it, which seemed to take care of the problem for the most part. Now I’m going to spray the cuttings with dish soap water as explained above and then add diatomaceous earth to the soil I pot them up in! Hopefully that will work! Thank you Laid-back Gardener for your post and suggestions on this subject!

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  6. Rob Blomquist

    I have never had a big infestation, just patches. I treat just like above the ground mealies, a sprayer of alcohol and water. It kills them the same. But this was years ago. today I try to keep the vitality of my plants high and I get no mealies at all. I cross my fingers.

    • I don’t think vitality has that much to do with it: both healthy and weak plants can be infested.

    • What type of alcohol you were using

    • I’ve unfortunately had Mealy bugs for about a year. It is on our New Zealand Tea tree plant which we’ve had for over 8 years. I think this problem started by overwatering the tree. We live in San Francisco and we’ve been told you could water a tree as much as you want because we have sand. Wrong! Tried these remedies per internet recommendations: Neem Oil, Insecticide, spraying rubbing alcohol, coffee grinds around base, baking soda, peroxide. I know, how could the tree still be alive? I think they are coming from the roots. The tree still has nice blooms, and there I find sometimes 5 to 10 of these daily. They are most likely hiding in the bark. We can’t pull the tree up to see what is happening in the roots. Any recommendations are appreciated.

      • You could dig into the ground near the tree and examine its roots to see. But root mealybugs and stem mealybugs are two different if related insects. Sure, a plant could have both, but it doesn’t follow that that would be the case. Stem mealybugs alone could be doing the damage and they’re very hard to eradicate. Here are some of my thoughts on them: https://laidbackgardener.blog/2018/12/14/when-mealybugs-attack/

      • Giving an update. I believe I don’t have the root mealy and they are just on the bark of the tree we have. I’ve been able to curb the number of mealy bugs to just a few every couple days. I spray 70 or 90% rubbing alcohol and not diluted. Initially I was worried about killing the tree but it looks fine and spraying alcohol is very easy and they die instantly.

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  8. I am dealing with soil mealies right now and am ding research on developing an ‘integrated pest management’ schedule to be rid of them. Basically it involves treating multiple times with insecticides that have different modes of action so that resistance doesn’t develop. The treatment schedule should be based on their life cycle to prohibit any immature ones from reaching adulthood AND to continue treating new larvae that hatch after your initial treatment. Not done yet.

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