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Leaf Spots in the Landscape

Elizabeth Little/Extension Specialist

Department of Plant Pathology, University of Georgia

 

Many areas in Georgia are experiencing warm, humid weather with frequent

thunderstorms this month. This is the perfect weather for fungal leaf spot

development in the landscape. Most leaf spots are benign and will not damage

the plant. Cercospora Leaf Spot of Hydrangea is an example of a leaf spot

disease that commonly occurs during prolonged wet weather or under sprinkler

irrigation. As with most leaf spots in the landscape, chemical treatment is rarely

needed. Some leaf spotting and leaf drop will not the harm the plant.

Management of leaf spot diseases involves removing sources of the disease and

protecting the plant. Start by selecting plants that will thrive where they are sited.

The fungi that cause these diseases mainly survive on the infected leaves that

fall to the ground, so removing and destroying diseased leaves can help lessen

the amount of disease next year. Stressed plants are more susceptible to

disease, so check the cultural conditions and optimize them with fertility

management and mulching. Good air circulation around plants will lower the

humidly and leaf wetness and reduce disease. Avoid wetting the leaves when

irrigating landscape plants.

If the plant is repeatedly defoliated each year or appears to be dying back

because of the disease, prune out the affected stems and use fungicides

preventatively (before the symptoms) to protect new growth.