Stippled Cannabis Leaves: Spider Mites or Mildew?
The situation
A vigorous outdoor Purple Pomegranate in a large coco container developed irregular pale marks on older fan leaves. Conditions were 67F and 62% RH, with dense foliage that could hold moisture through cool mornings.
The flowers remained healthy, resinous, and actively growing. There were no dead brown centers, fuzzy mold, burned tips, or other signs of bud rot, but one marked leaf showed fine stippling and a thin strand.
The diagnosis
The marks were stippled rather than clearly powdery. Powdery mildew usually forms distinct flour-like colonies that wipe away and return. These photos were too soft to confirm that coating, while the fine dots and possible strand made spider mites the stronger lead.
The damage was concentrated on older leaves, but it did not resemble a mobile nutrient shortage. There was no vein-related chlorosis, edge burn, or progressive whole-plant decline. Persistent localized speckling after pH and feeding corrections also made residual uptake damage less likely.
The solution
- After morning dew dries, inspect the undersides of 10 stippled fan leaves with a bright flashlight.
- Tap each inspected leaf over white paper. Crawling dots strongly support mites or another sap-feeding pest.
- Take one sharp close-up of a damaged leaf underside within 48 hours.
- Do not spray the flowers until the cause is confirmed. Look for moving dots, fresh webbing, or white powder that wipes off and returns.
- Keep the rain cover open on every side, keep flowers dry, and remove only dead leaves, staying below 10% of total foliage.
- Water only when the upper 2-3 inches have dried enough to confirm the large container is ready.
How to avoid this
- Check older fan-leaf undersides weekly because mites often establish there before reaching flowers.
- Keep dense canopies open enough for air to pass through without heavy mid-flower defoliation.
- Prevent dew, irrigation, and condensation from sitting on flowers.
- Quarantine new plants and inspect outdoor clothing or tools before working near the canopy.
- Treat confirmed pests early, before webbing appears and while flowers are easier to protect.
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