Large spots and leaf discoloration on hydrangea macrophylla - Ask Extension
Hoping to assign this to Jill Pollok. I have four established macrophylla hydrangea that have large spots and leaf discoloration, deep inside the shru...
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Large spots and leaf discoloration on hydrangea macrophylla #870288
Asked May 27, 2024, 3:03 PM EDT
Hoping to assign this to Jill Pollok. I have four established macrophylla hydrangea that have large spots and leaf discoloration, deep inside the shrub is where I am seeing them, some of the leaves are almost all white. I am familiar with Cercospora leaf spot and these hydrangeas will exhibit that disease but usually later in the season. This looks different. I would say perhaps 5-10% of each shrub is affected. The 3 shrubs are sporting healthy young blossoms. There is no overhead irrigation.
Sussex County Delaware
Expert Response
The spots definitely look like fungal leaf spots, it's possible this is anthracnose and not Cercospora leaf spot. Anthracnose (caused by Colletotrichum spp.) can cause larger leaf spots and eventually leaf blight if wet weather persists. As for the white leaves, has the soil been tested for nutrient levels and pH? If the plant looks healthy otherwise, I would try pruning to increase airflow and maybe applying a preventive fungicide.
