Downy mildew guide image
Plant disease guide

Downy mildew

Symptoms: Yellow patches on upper leaf surfaces with gray, white, or purple fuzzy growth underneath.

Symptoms: Yellow patches on upper leaf surfaces with gray, white, or purple fuzzy growth underneath.Prevention note: Keep foliage dry overnight and avoid crowding in humid conditions.

Quick facts

Symptoms: Yellow patches on upper leaf surfaces with gray, white, or purple fuzzy growth underneath.

Organic treatment / management:

Prevention note: Keep foliage dry overnight and avoid crowding in humid conditions.

  • Remove infected leaves.
  • Improve airflow.
  • Water in the morning at soil level.
  • Use copper products preventively if appropriate.

What to do next

  • Remove the worst infected or damaged tissue when appropriate.
  • Improve airflow, spacing, sanitation, and watering habits.
  • Avoid overhead watering when leaf disease is suspected.
  • Use organic fungicide or copper products only when the label fits the plant and disease.
  • Discard confirmed viral infections rather than propagating from them.

Watch-outs

Do not compost severe disease material unless your compost system gets hot enough to destroy pathogens.

FAQ

How do I use this plant disease guide?

Start with the light, soil, water, symptom, or purpose notes on this page, then make one careful change at a time.

What is the biggest mistake with Downy mildew?

Do not compost severe disease material unless your compost system gets hot enough to destroy pathogens.

When should I get more help?

Get local help if the plant is valuable, symptoms are spreading quickly, or outdoor disease and pest problems may affect nearby plants.