Downy Mildew on Basil

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Downy mildew on basil was first detected in Florida in 2007.  Beginning in 2008 there were a number of infections reported in the eastern US. It was found in greenhouse, home, and field-grown basil. 

Cornell University has extensive information on this problem.

Below are  photos showing the early symptoms of this fungal disease on the top and bottom sides of basil leaves.

downy mildew on basil

Downy mildew on underside of leaf

downy mildew on basil

Leaf yellowing symptom on basil

downy mildew basil 2

Gray fuzzy growth on leaf bottoms

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.

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