Powdery Mildew
🔎 Find by symptom
About this condition
Powdery mildew is a fungal disease caused mainly by the order Erysiphales, producing a white powdery coating on leaves and new shoots. It is commonly seen on bonsai such as ume, cherry, maple, and rose, and can affect appearance and vigor.
Common symptoms
- White powdery coating spreads across leaf surfaces
- Affected areas become distorted and curled
- Symptoms tend to originate on new shoots and young leaves
- Severe cases may cause premature leaf drop
Common causes
- Poor air circulation combined with high humidity
- Overly dense foliage trapping stagnant air
- Excess nitrogen fertilization producing overly soft new growth
- Large day-to-night temperature fluctuations in spring and autumn
Prevention (growing conditions & routine care)
Position trees in locations with good air flow and thin out overcrowded foliage through formative pruning. Avoid excess nitrogen fertilization and choose drier placement for susceptible species.
Related guide
→ Browse the species guide for this animalWhen to see a vet
Monitor; consult a specialist if it worsensWhat can a nursery or grower do?
Specialist bonsai nurseries can advise on management approaches tailored to the tree species and severity, including adjustments to pruning practices and fertilization balance.
Related columns
- How to Choose a Bonsai Pot | The Basics of Matching Pots to Tree Species and Shape
- Leaf Pruning of Deciduous Bonsai (Hagari) — A Summer Technique to Promote Smaller Leaves and Finer Branching
- Beginner Bonsai: Year-One Growing Schedule by Species
- Bonsai Root Growth and Healthy Root System Development: Root Establishment Management and Repotting Timing
Other problems with this plant
Root RotConsider acting within a few daysSooty MoldConsider acting within a few daysAphidsMonitor; consult a specialist if it worsensScale InsectsConsider acting within a few daysSpider MitesMonitor; consult a specialist if it worsensLeaf Scorch / Water StressMonitor; consult a specialist if it worsensBorer (Longhorn Beetle Larva)Act promptly (isolate, remove the cause)