Copper Spots on Hydrangeas

Identification

• Hydrangea plants are susceptible to rusts, which are infections caused by numerous fungi. Untreated rusts cause severe branch dieback and are likely to kill the entire plant.

Damage

• Rust infections are characterized by the appearance of dry, reddish yellow, orange or copper masses and pustules of fungal spores on infected foliage. The fungal growth is more pronounced on foliage undersides. Affected leaves gradually yellow, brown and drop prematurely. Tissue swellings or galls and cankers appear on the trunk. Foliage is frequently distorted, discolored and dwarfed.

Control

• The use of overhead irrigation keeps moisture on plants for extended periods. This excessive moisture favors fungal growth. Remove all infected leaves from under the plants and prune out infected branches. Apply fungicides in spring to reduce chances of infection later.