Plant care guide

String of Pearls Mealybugs: Alcohol, Soap or a Systemic?

Updated

Why does my String of pearls have mealybugs systemic?

White, cottony tufts tucked between the pearls, at stem joints or at the soil line are usually mealybugs. Extension sources treat systemic soil insecticides as a last resort indoors: they are less reliable against mealybugs and carry risks in homes with pets or children.

What to do first

Isolate the plant, remove what you can see, and dab or spray mealybugs with diluted rubbing alcohol after a test patch. Repeat weekly. For a heavy or root infestation, take clean cuttings and discard the rest before reaching for a systemic product.

Mealybugs love the tight tangle of a string of pearls. They tuck in where pearls meet the stem and at the crown, where they are easy to miss until the plant is already weak. Finding them early makes a big difference, because each female can lay a large batch of eggs.

The good news is that you rarely need a systemic insecticide. Extension guides put alcohol, soap and cuttings first, and treat systemics as a careful last step.

Confirm it is mealybugs

Clemson HGIC describes mealybugs as small, pale insects about 3–6 mm (⅛–¼ in) long, covered in white, waxy material that makes them look cottony. On string of pearls, check:

  • Between pearls and where they attach to the stem.
  • The crown, where stems leave the soil.
  • Leaf joints and the rim of the pot.
  • The roots, if the plant is declining with no visible insects. Clemson notes that one mealybug species feeds on roots.

Other signs, per UC IPM: sticky honeydew, black sooty mold growing on it, white cottony egg masses, and ants visiting the plant. UC IPM adds that ants protect mealybugs from their natural enemies, so keep ants away.

Step 1: isolate and remove

Move the plant away from others now. Clemson advises keeping it separate until the pest is completely controlled. Iowa State University Extension recommends scouting often and dealing with pests right away.

Pick off visible clusters with a cotton swab or a toothpick. Snip out badly infested strands; on string of pearls, the stems are easy to replace.

Step 2: alcohol, then soap or oil

UC IPM gives the clearest method for houseplants:

  1. Test first. Dab a little alcohol on a few pearls one to two days before treating, and check for leaf burn.
  2. Spot-treat. Dab mealybugs with a 70% (or weaker) isopropyl alcohol solution on a cotton swab.
  3. Spray for larger outbreaks. UC IPM describes a 10–25% isopropyl alcohol solution in a spray bottle, repeated every week until the infestation is gone.
  4. Add soap or oil if needed. UC IPM says insecticidal soaps, horticultural oils and neem oil applied directly to mealybugs give some suppression, especially of young nymphs. Test for damage first.

UC IPM notes that the waxy coat of adults and their habit of hiding make contact products less effective, and that no product will kill every individual. Keep checking and retreat as needed.

Step 3: take clean cuttings

When an old plant is heavily infested, starting over is often easier than rescuing it. UC IPM suggests considering discarding houseplants rather than repeatedly treating them. Clemson and Iowa State also mention discarding plants with severe infestations.

NC State Extension notes that string of pearls tends to die back after several years and is easily renewed from 7.5–12.5 cm (3–5 in) stem cuttings with a few nodes covered in mix.

  1. Choose strands you have inspected closely and found clean.
  2. Rinse them and check again.
  3. Root them in fresh cactus mix in a clean pot.
  4. Bag and discard the old plant and its soil.

If you find mealybugs on the roots, do this rather than treating the soil. UC IPM says root-feeding mealybugs are even harder to control than those above ground.

What about systemic insecticides?

Systemic products are taken up by the plant, usually from granules or spikes in the soil. Here is what the extension sources say:

  • UC IPM: spikes or granules containing imidacloprid may reduce mealybug crawler numbers on houseplants. They are less reliable against mealybugs than against other sap-feeding insects, and their use should be avoided when possible.
  • Clemson HGIC: imidacloprid granules for soil application are sold for houseplants. Only a few pesticides are labeled for indoor use on houseplants.
  • Iowa State (2024): granular soil insecticides are available but pose risks in homes with pets or children.
  • Iowa State (2004): use of a granular soil-applied systemic was discouraged because of toxicity concerns.

If you still choose one, Clemson’s guidance on indoor pesticides applies: the product must be labeled for indoor houseplants, the plant type must be on the label, and the label directions are the law. Keep children and pets away from treated plants, and test on a small area first. Do not use garden or outdoor-only products indoors.

Keep it from coming back

  • Inspect new plants before they join the others. Iowa State suggests a 7–10 day quarantine.
  • Recheck the crown and pearl joints weekly for a month after treatment.
  • Avoid overfeeding. UC IPM notes that too much nitrogen fertilizer stimulates new growth, where mealybugs prefer to lay eggs.

String of pearls itself is a concern around pets. NC State lists it as a problem for cats, dogs and children, with vomiting and diarrhea after ingestion and sap that can irritate skin.

See the string of pearls hub for other guides.

Other string of pearls problems we cover: sunburn, underwatering.

References

How this guide was put together: UC Statewide IPM Program, Clemson HGIC, Iowa State University Extension and NC State Extension guidance.

Other String Of Pearls problems

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Knowledge record: GR-10020