Powdery Mildew
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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
- Complete Bonsai Tree Selection & Development Roadmap for Beginners | Phase-by-Phase Management Strategy from Year 1 to Year 5
- Bonsai Aged Wood Techniques | Creating Branch Aging Expression and Tree Age Aesthetics
- How to Prevent Fertilizer Burn in Bonsai | Determining the Right Fertilizer Amount and Concentration
- A Guide to Giving Bonsai as Gifts | Appropriate Species and Etiquette for Longevity Celebrations and Business Opening Celebrations
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)