White Spots / Powdery Mildew
White powdery patches on leaves are typically caused by powdery mildew, a common fungal issue. Other white spots may be mineral deposits or pest related.
Causes possibles
Powdery Mildew Fungus
Why: Thrives in warm, humid conditions with poor air circulation. Spreads via airborne spores.
Signs to check: White powdery coating on leaf surfaces, starts in patches and spreads, leaves may distort.
Hard Water Deposits
Why: Mineral-rich tap water can leave white crusty spots on leaves after misting or overhead watering.
Signs to check: Spots are crusty rather than powdery, appear where water droplets dried, can be wiped off.
Mealybug Residue
Why: Mealybugs produce white, cottony masses that can be mistaken for mildew.
Signs to check: White fluff concentrated at leaf joints and stem bases, sticky residue present.
Quoi verifier
- 1Try wiping the white substance — does it come off easily?
- 2Check if the coating is powdery (mildew) or crusty (mineral)
- 3Inspect for cottony clusters and sticky residue (mealybugs)
- 4Assess air circulation around the plant
Que faire
- Improve air circulation by spacing plants apart or using a fan
- Remove heavily affected leaves and dispose of them
- Avoid overhead watering and misting affected plants
- Apply a baking soda solution (1 tsp per quart of water) as a mild fungicide
- Use filtered water for misting to prevent mineral deposits
Quand chercher de l'aide
- Mildew is spreading rapidly to other plants
- Leaves are yellowing, distorting, or dying beneath the coating
- Plant is losing vigor despite treatment
Point cle
Distinguish between fungal mildew, mineral deposits, and pests before treating. Improved air circulation is the best preventive measure.
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Sources: Missouri Botanical Garden, RHS. Contenu compile a partir de references horticoles accessibles au public a des fins educatives. Les organisations sources sont listees pour la transparence uniquement et n'impliquent pas d'approbation.