Grow It Eat It: Maryland's Food Gardening Network

Downy Mildew of Basil

Look out for downy mildew on your basil plants

Reports of downy mildew on basil are cropping up around the state. This is a relatively new disease for East Coast states. HGIC hort consultant Marian Hengemihle was saddened this week to find it in her home garden. Here are some photos showing the early symptoms of this fungal disease on the top and bottom side of basil leaves.

Leaf yellowing symptom on basil (click to enlarge)

Gray fuzzy growth on leaf bottoms (click to enlarge)

Leaf yellowing is the most noticeable symptom. Infected leaves will then blacken and die. The disease can enter your garden on seeds or transplants. It spreads quickly and widely via fungal spores carried by air currents. Monitor your plants closely for symptoms and be prepared to pull out, bag up, and throw out infected plants. It is safe to eat leaves from infected plants- the disease does not harm people. If you lose plants to downy mildew you can sow fresh seed in containers or in another part of your garden.

Warm, wet, humid weather encourages the spread of downy mildew. Plant basil in full sun locations and don’t crowd your plants. Good air circulation around plants can help reduce the risk of infection.

Cornell University has extensive information on this problem and Adrian Higgins recently reported on it for the Washington Post

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For more information, contact Jon Traunfeld

Last updated: 07/19/2011