White cottony or waxy clumps in leaf axils and stems
Clumps in protected spots (node junctions, under leaves) that grow slowly; honeydew follows..
- Also called
- white fluff on stems
- cotton balls on plant
- white waxy bugs
- mealybugs
Likely causes, most likely first
Ranked for this sign on its own. Your stage, medium and readings change the order, so run the checker for your plant.
PossibleMealybugs
Fix: Remove colonies with a cotton bud dipped in 70% isopropyl alcohol (veg only, test a leaf first); release mealybug predators (e.g. Cryptolaemus beetles) or parasitoids; quarantine new stock; discard heavily infested plants.
Recovery: No new cottony clusters after 2 weeks.
How to confirm it
- Magnifier check of leaf undersides and new growth. Use a 10-20x loupe for spider mites, thrips, aphids and whiteflies, and a 30-60x lens or clip-on phone macro for broad and russet mites. Check the undersides of 10 affected leaves across several plants and the newest shoot tips, in white light. Look for moving dots, eggs, shed skins, webbing, slender insects with black specks, and glassy specks on new growth.
Look for
Waxy white clusters that, when prodded, contain oval segmented insects..
The full guide: Mealybugs and root mealybugs on cannabis: ID, life cycle in numbers and IPM
Guidance, not a guarantee. The checker weighs common causes against what you tell it; confirm with the tests before you treat, change one thing at a time and watch the new growth.
