Gardening Harmful insects Houseplants

Last Chance Mealybug Save

Ill.: &, montage:

Is a favorite houseplant infested with mealybugs or scale insects? What a disaster!

Treating mealybugs or scale insects with a cotton swab dipped in rubbing alcohol is unlikely to ever work. Photo:

In spite of tales on the Internet of people having controlled either pest with a cotton swab dipped in rubbing alcohol, I don’t think anyone, ever, has gotten rid of them that way. You always miss at least one, then, months later, just when you’re finally basking in the success of your treatment … they’re ba-ack! 

Three white mealybugs.
Just when you think the mealybugs are under control, back they come! Photo:

Mealies and scale are just about impossible to control, so make sure you isolate new plants (almost all of such infestations start with an infected plant brought into the home) after a 40 day quarantaine (quarantine means 40 days: you knew that, right?) and be prepared to toss them if it turns out they’re infected.

Scale insects cover a branch.
Scale insects: mealybugs with a shell. Photo:

I’ve even learned, although it took me years to do so, to simply get rid of any new plant I buy that turns out to have either mealybugs or scale. Without qualms … well, scarcely any. 

So, mealybugs mean … bye-bye plant. Scale insects? Burn, baby, burn! Just get rid of any plant that is infested with either bug. Trust me: I’ve learned the hard way. (Read The 30 Year Mealybug Infestation: A Horror Story.)

The Method of Last Resort

But there is a method of last resort you might want to try to save a plant, one that just might work. If you’re brave enough to try. 

It has worked for me, a handful of times. And, yes, sometimes failed miserably. But here it is:

Sometimes You’ve Gotta Be Cruel to Be Kind

First, this has to be a plant of great valuable, something nearly irreplaceable. Perhaps your great-grandma’s ficus or a one-in-a-million mutation you discovered. Because what you are going to do to the plant is pretty drastic. 

The plant is probably big—and old. Mealies are hiding out in its crevices. Scale insects at its leaf bases. What are you possibly going to do to? 

Potted indoor tree before pruning and after pruning, with all leaves removed.
Cut off and destroy all the green parts, stems and leaves. You’ll only want to keep enough of a structure so the plant can regenerate. Ill.:,, avpng & StikPNG, montage:

The answer is: cut it back, way back. Every leafy branch must go. Both mealybugs and scale insects tend to settle on new growth: soft stems their mouth parts can readily pierce, new leaves, etc. They’ll be very few elsewhere. So, chop, chop, chop, leaving your plant looking like a plucked chicken: only a trunk and shortened branches. Sterilize the pruning shear or saw with rubbing alcohol between each cut. I mean, you’ve always promised you’d follow that rule. Well, this time, really do it!

Helpful Hint: This technique will only work on plants capable of regenerating from their branches, trunk or base … a group that does include the majority of houseplants. Exceptions include palms and conifers, few of which have dormant buds capable of springing into action after hard pruning.

Ideally, you’d do this heavy pruning outdoors and send the trimmings straight into a trash bag … or a roaring fire. 

Pull what’s left of the plant out of its pot. Don’t use the pot again until it has been sterilized. And you won’t have time for that today!

Remove most of the soil. Toss it! Yep, in the trash! Hose the plant down, head to foot. 

Cut back tree being washed in soapy water.
Clearn the entire plant en soapy water. Ill.:, avpng, clipart.png, & StikPNG, montage:

Now, get a pail of soapy water and a sponge or old rag, and soap everything down: stem, trunk, exposed roots, etc. Soap is deadly to most insect pests and certainly to mealybugs and scale. Slosh it into every nook and cranny. 

Next, hose the plant down again. Really blast it! You might just knock that one last mealybug, barely clinging to life, into oblivion!

If the plant will be returning to its usual indoor habitat, clean that up too. Soapy water and old rag again: clean the plant shelf, the floor, the wall, the window pane. Slosh lots of water around, making sure the slightest crack is drenched.

And you could still be contaminated, so now go take a shower. And change your clothes.

The Aftermath

Now, the stub of the plant is clean (hopefully) and you’re clean (assuredly). Time to repot. In fresh soil and a clean or new pot. Water well. Put the plant in the best light possible, but isolated from any other plant. And wait.

And wait.

And wait.

Sometimes, nothing happens. Months go by with no new growth. Try scratching the stem’s outer bark with a thumbnail. If there’s nothing green underneath, it’s dead. Failure!

My own dragon tree (Dracaena draco) never recovered from my attempt to save it. Photo:

That happened to me once with a huge dragon tree (Dracaena draco) I’d grown from seed brought from its native Canary Islands. That big, fat, barren trunk stood there for a full year before I finally gave up and tossed it. Apparently, it had no dormant buds on the lower part of its trunk. Nothing to grow back from. Who knew? 

Illustration of potted tree cut back severely and now resprouting.

Nine times out of ten, though, the plant regenerates. Abundantly. Surprisingly. Fresh new leaves galore. Soon new stems too. And often within only weeks.

Ill.:,, avpng, clipart.png, & StikPNG, montage:

And about half the time, though, after about 6 months the dreaded pest is back. I’ve never been able to save a Solandra, for example, nor a bay laurel (Laurus nobilis) or oleander (Nerium oleander), for example. The pest always returns.

My jacaranda turned out to be the Typhoid Mary of scale insect carriers. I should have destroyed this plant the first time the treatment failed! Photo:

I tried 5 times to save a jacaranda (Jacaranda mimosifolia), a cherished souvenir of my first trip to Los Angeles nearly 40 years ago. I should have ditched that one 20 years ago: it was the Typhoid Mary of scale insect carriers, infecting plant after plant after plant. What an idiot I was to hold onto it!

Old beaucarnea with thick trunk and multiple taps
To be honest, I’ve had to treat my ancient beaucarnea (Beaucarnea recurvata) twice, but after that, it turned out to be a success story: it’s been mealybug free for a decade now. Photo:

But then there are first-time successes, still going strong. Citrus, ficus, dracenas: my indoor garden wouldn’t be what it is without them and I’m glad I made the extra effort. Although I hope never to have to again.

Tough Love

New plants don’t get that kind of extra care. If I bought a plant recently and mealies or scale show up, first the salesperson gets an earful (and I get a reimbursement: I can be pretty convincing). And I figure if I got it not too long ago, it’s still bound to be readily available somewhere … so I look and find one-from another source. And try again. 

My battles with mealies and scale are legion, legendary even. Yet, they’re pretty much in the past. I’ve gotten so much more careful with isolating plants that few creepy crawlers get past me. None have in years. But there are still some houseplants I’ve owned for ages that I’d still fight tooth and nail to save if ever they became infested!

So take that, mealies! Kapowy, scale insects! I’m out to win!

Garden writer and blogger, author of 65 gardening books, lecturer and communicator, the Laidback Gardener, Larry Hodgson, passed away in October 2022. Known for his great generosity, his thoroughness and his sense of humor, he reached several generations of amateur and professional gardeners over his 40-year career. Thanks to his son, Mathieu Hodgson, and a team of contributors, will continue its mission of demystifying gardening and making it more accessible to all.

4 comments on “Last Chance Mealybug Save

  1. Surprising. I had a scale infestation on my office plants (it killed some). When I realized what’s happening I sprayed all of them with undiluted isopropanol maybe 3 times within 2 weeks (outdoors). Yup 99.9% not the 70% you get from drugstore. The scale were gone and haven’t showed up for 1.5 year now. I didn’t even know that they are supposed to be difficult… Some plants did not like it, but honestly only ficus showed some burned leaves and philodendron unfurling leaf died, but the whole plants were ok. Still better than loosing all of them to trash. I do this in the case of every pest I see and not one pest survived so far… ZZ, monstera, hoya, ferns, calatheas, pothos, orhids, succulents, ivy, pilea, dracena, shefflera, coffee plant, palms, peperomia, spathyfilium, and unfurled philodendron leaves take 100% isopropanol with no problem. For ficuses I swipe them now, not spray, and have no burned leaves either. I haven’t also see any stunted growth after treatment, but usually removal of pests leads to the explosion of new growth so I might have missed the stunting effect if it happened.

  2. I never even tried to get rid of scale on my Ficus benjamina. I just put them outside at the end of winter, and bring them back in before summer gets too warm. Predatory insects seem to control them better outside, even though it is not far from where they live inside. Well, it never got rid of the scale, but it controlled it enough that the sticky honeydew was tolerably minor for another year. By the time it got bad again, it was time to put the trees out again.

  3. I agree that mealybugs and scale are next to impossible to eliminate. There is an exception (mostly only available to your USA readers) and that is Imidacloprid. Two years ago almost all of my 50 cacti were heavily infested with mealybugs and I had been struggling with scale on a 40 year old ficus. Using properly diluted Imidacloprid, over the course of one summer I eliminated them all. It’s been 2 years and not a sign of them anywhere. For obvious reasons I would only consider this for potted houseplants.

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