What Causes Brown Spots on Hydrangea Leaves?

mrhayata/CC-BY-SA 2.0

Brown spots on the leaves of hydrangea shrubs are mainly caused by leaf spot diseases, which can either be fungal or bacterial in nature. Cercospora leaf spot and anthracnose are common fungal infections that affect hydrangeas, while bacterial leaf spot is commonly caused by the pathogen Xanthomonas campestris.

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