Mealybugs on houseplants: how to identify and get rid of them

Mealybugs are small, soft insects covered with white wax that cluster in leaf axils, along stems and sometimes on the roots, sucking sap and leaving sticky honeydew. To get rid of them, dab every visible bug with 70 % isopropyl alcohol on a cotton swab, then spray insecticidal soap or horticultural oil every 7–10 days for 4–6 weeks; heavily infested plants are often better discarded.

What mealybugs look like

Adults are oval, segmented insects about 1/8 to 1/4 inch long, coated in powdery white wax, according to Clemson HGIC. They move slowly and cluster where they're protected: leaf axils, the crown of a rosette, branch forks, under leaves and on stems near the soil.

UC IPM lists the signs of an infestation:

• white, cottony egg masses on the plant
• waxy white residue on stems and leaves
• sticky honeydew on leaves, furniture or the floor
• black sooty mold growing on that honeydew
• ants visiting the plant to feed on honeydew

The most common mealybug on indoor ornamentals is the citrus mealybug (Planococcus citri), with short, even wax filaments around the body. The longtailed mealybug has two tail filaments longer than its body and gives birth to live young instead of laying egg sacs.

Early signs of mealybugs

Before you see the cotton, you may notice slower growth, a few yellowing leaves, a faint stickiness on the leaves below an axil, or a single white speck in a spot you can't quite reach. Squash a suspect speck on a tissue: a mealybug leaves a yellowish or reddish smear; a fleck of perlite or mineral deposit doesn't.

Mealybugs vs. look-alikes

Where mealybugs come from and how they spread

Mealybugs don't come from the soil, overwatering or "dirty" air. Colorado State Extension notes that infestations of scale, mealybugs and whiteflies are almost always started by an infested plant recently bought or received as a gift, and recommends quarantining new plants for at least three weeks.

Females lay 100–200 or more eggs in cottony sacs over 10–20 days, and many species reproduce without mating (UC IPM). The newly hatched crawlers are yellow to pink, wax-free and mobile; they walk to new feeding sites or neighboring plants and then settle and cover themselves with wax. Indoors there is no winter break, so all stages are present year round.

Plants that get hit most: succulents and cactus, jade plant, hoya, African violet, croton, orchid, hibiscus, citrus such as Meyer lemon, and pothos.

How to get rid of mealybugs on indoor plants

1. Isolate and inspect

Move the plant away from other pots. Look in every leaf axil, under each leaf, along stems, under the pot rim and in the drainage holes. Check neighbors that were touching it.

2. Remove what you can see

• Alcohol swabs: UC IPM recommends dabbing with a solution of 70 % (or less) isopropyl alcohol for houseplants, testing a small area first because alcohol can burn some leaves. Clemson calls cotton swabs dipped in rubbing alcohol effective for light infestations.
• Prune heavily infested shoots and bag them before they go in the trash.
• Rinse larger plants with a strong stream of water to knock off exposed colonies.

3. Spray the whole plant

Use insecticidal soap or horticultural/neem oil. UC IPM notes that the waxy coating and hiding habit make contact sprays less effective on adults, but they kill exposed crawlers and young nymphs. Wet all surfaces, including leaf undersides and stems. Don't substitute dish soap: Colorado State points out that household detergents aren't tested for plants and can injure them.

4. Repeat on a schedule

The plant can go back with the others after three consecutive weekly checks with nothing found.

5. Systemic option for stubborn cases

On non-edible plants, imidacloprid granules labeled for houseplants are taken up by roots and reach mealybugs in places sprays miss, including the roots. They are slow (1–3 weeks) and must never be used on herbs or fruiting plants. Details and cautions are in our systemic insecticide guide.

Root mealybugs

Some species live in the soil. UC IPM lists ground mealybugs (Rhizoecus) as damaging mostly to potted plants such as African violets. Suspect them when a plant wilts or stalls despite correct watering and you find nothing above ground.

Slide the plant out of its pot: root mealybugs look like white waxy specks or patches on roots and on the inside of the pot wall, sometimes mistaken for perlite or mold. To treat:

1. Remove old soil completely and rinse the roots.
2. Trim damaged roots.
3. Discard the soil and scrub the pot, or use a new pot.
4. Repot into fresh mix (see repotting).
5. Recheck in 3–4 weeks; on ornamentals a labeled systemic soil treatment is the follow-up if they return.

When to throw the plant out

UC IPM and Clemson both say a severely infested houseplant may be best discarded. That is often the right call when mealybugs are in every axil, on the roots, and the plant is inexpensive or easily replaced. For a favorite plant, take a cutting from the cleanest tip, swab and rinse it, root it in quarantine and discard the rest.

What doesn't work

• Single treatment. Egg sacs and hidden crawlers guarantee a comeback in 2–3 weeks.
• Spraying only the tops of leaves. Mealybugs sit in axils and under leaves.
• Heavy feeding to help the plant recover. UC IPM notes that excess nitrogen pushes soft new growth that mealybugs prefer.
• Releasing ladybugs indoors. Common garden ladybugs leave or die; the mealybug destroyer beetle needs warm, large plantings, as Colorado State notes.

Prevention

• Quarantine every new plant for three weeks and inspect axils and roots before it joins the others.
• Look under the pot rim and in drainage holes when buying.
• Check plants every time you water; a single tuft is easy, a colony isn't.
• Keep plants from touching.
• Wash pots and tools after handling an infested plant.

For other pests that cause sticky leaves, see scale insects and whiteflies, or the overview of common houseplant pests.