White Spots or Patches on Cannabis
White on cannabis leaves can mean powdery mildew (bad), trichomes (good), mite damage (bad), or calcium spots (bad). The pattern tells you which.
What it looks like
- ●Powdery mildew: white DUSTY or FUZZY patches that wipe off
- ●Trichomes: tiny sparkly crystal hairs (natural, only in flower)
- ●Mite damage: tiny white/yellow pinprick dots (stippling)
- ●Calcium spots: white-centered brown rust spots
Quick diagnostic checks
Measure before you treat
Plant diagnostic essentials
These tools help confirm the cause of white spots before you change nutrients, watering, or the environment.
Carson MicroBrite Pocket Microscope
Inspect leaf undersides for mites, eggs, mildew, and harvest-ready trichomes.
Check price on AmazonGovee Bluetooth Hygrometer
Track temperature and humidity trends instead of guessing from one reading.
Check price on AmazonAC Infinity CLOUDLINE T4
Automate airflow to manage heat, humidity, and mold pressure.
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Causes ranked by likelihood
1. Powdery mildew (most urgent)
Most commonSigns
- ●Dusty patches that wipe off
- ●Spreading fast
- ●High humidity
Fix
- ✓See full powdery mildew guide — act fast
2. Spider mite stippling
CommonSigns
- ●Pinprick-sized dots
- ●Tiny specks moving on undersides
- ●Fine webbing
Fix
- ✓See spider mite guide — neem spray, predatory mites
3. Trichomes (this is normal!)
CommonSigns
- ●Sparkly crystal-like hairs
- ●Only on flower-stage plants
- ●Concentrated on buds and sugar leaves
Fix
- ✓Nothing — trichomes = potency. This is what you want.
⚠️When to worry
PM or mites = urgent action today. Trichomes = relax.
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