Diagnostic Guide
Why is there white powder on my plant leaves?
Confirm that the coating sits on the leaf surface before treating it like a nutrient issue.
Last reviewed: August 6, 2026 · Sources: University of California IPM
Quick Diagnosis
Start with the visible pattern
| What you see | Most likely cause | Check first |
|---|---|---|
| White coating with crowded foliage | Powdery mildew | Check airflow and plant spacing |
Field Check
Compare shaded and crowded plants to more open ones. Mildew often shows up first where airflow is limited.
Do This First
Simple checks before you buy anything
Most garden problems have more than one possible cause. Start with the simplest explanation.
- Remove heavily affected leaves first.
- Reduce crowding before buying treatments.
- Avoid wetting foliage late in the day.
Likely Causes
Most likely causes to check first
Powdery mildew
Confidence: 95%Powdery mildew creates a white, dusty coating on leaves and spreads more easily where airflow is poor.
- Look for a dusty white coating on leaf surfaces.
- Check whether crowded growth is limiting airflow.
- Remove a leaf and compare symptoms across several plants.
Sources
Reference material used on this page
University of California IPM
Powdery mildew identification and control
Publication date: 2025
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