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Caption: Mycosphaerella leaf spot, www.forestryimages.org
Photo by: B.J. Jacobsen, NCSU
  
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Hydrangea : Fungal leaf spots
(revision date: 4/23/2014)


Biology
Several fungal diseases cause spotting of leaves on hydrangeas. Symptoms may include brown, black, or gray spots or angular blotches. These may be surrounded by a reddish or purple halo. Spotting may range from mild to severe and severely affected leaves may turn yellow and drop from the plant. Leaf spot diseases are usually noticed in midsummer to early fall. Cercospora leaf spot typically causes small necrotic spots beginning on the lower leaves and progressing upward on the plant. Anthracnose may cause large, round or angular blotches which can appear all over the plant, including the flower heads. Both of these diseases can be spread by splashing water and diseased plant materials including fallen leaves.
Management Options

Non-Chemical Management
  • Avoid overhead watering.
  • Space plants and prune to improve air circulation.
  • Use good sanitation. Remove and destroy or dispose of diseased plant materials. Clean up fallen leaves and debris beneath plants. Do not compost diseased materials.
  • Maintain plant health with proper nutrition and irrigation. Healthy plants are more disease-resistant and more tolerant of minor damage.
  • Avoid overfertilizing, which encourages lush, tender growth that is more susceptible to disease. If fertilization is necessary, use a slow-release or lower-nitrogen formula to maintain moderate growth.
Select non-chemical management options as your first choice!

Chemical Management


None recommended. Leaf spot diseases on hydrangea are seldom severe enough in the home landscape to warrant chemical control.

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Caption: Mycosphaerella leaf spot, www.forestryimages.org
Photo by: B.J. Jacobsen, NCSU