White, cottony clumps where the leaf meets the stem, or tucked into new growth, are usually mealybugs. They are small sap-sucking insects that hide in a waxy white coat.
How to confirm
- White fluff in leaf joints, under leaves or on stems, sometimes with a sticky film below.
- Leaves that yellow, curl or drop, and slow growth.
- A cotton-like patch that, when poked, shows a small soft insect.
What to do
- Move the plant away from others. Mealybugs spread.
- Wipe off the insects with a cotton bud or cloth dipped in rubbing alcohol (isopropyl) diluted with an equal amount of water. Test on one leaf first, as some plants are sensitive.
- Spray or wipe the whole plant, including undersides and joints, with a mild soapy solution or a plant-safe insecticidal soap, following the label.
- Repeat every week for at least three to four weeks. Eggs hatch later, so one treatment is not enough.
- Check the soil surface and the pot rim, and neighbouring plants.
- Cut away badly infested leaves and throw them away.
Prevention
Look closely at new plants before bringing them home, and keep them apart for two weeks. Check under leaves when you water.
When to scan
If you are not sure it is mealybugs, take a close-up photo of the white patch in daylight and scan it. Other pests and even harmless white deposits can look similar.