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Anthracnose is a fungus disease that causes irregular brown spots on bigleaf hydrangea flowers and leaves. Splashing water spreads fungus spores to the plant. The brown spots often measure more than 1 inch across and may develop dead tissue that gives the spots a bullseye appearance.
In respect to this, how do you get rid of brown spots on hydrangeas?
Leaf spots To control leaf spot, avoid watering your hydrangeas from overhead, and again, remove and destroy diseased plant parts. If summer rains make the problem worse, try a fungicide such as Immunox (always follow label directions).
Likewise, people ask, why do my hydrangeas have brown spots on the flowers?
All hydrangeas will turn brown if they wilt too many times in hot weather. Water these shrubs deeply every few days in the heat of the summer (note that hand watering isn't deep enough) and mulch around plants to hold moisture in the soil longer.
Rust, like leaf spot diseases, is caused by a fungal pathogen. Spores spread via wind or splashing water to hydrangea leaves. Rust appears on foliage as masses of dry, orangish spore pustules primarily on leaf undersides while the upper leaf surface turns yellow or brown. Infected hydrangea leaves may drop early.