Sick Sycamores

The leaves of many trees and shrubs turned brown and black this spring as a result of frost damage. In addition to suffering from this environmental stress, sycamores trees have also been troubled by fungi this spring. Anthracnose is a common fungal disease of sycamore trees and also causes browning of the leaf tissue. With freezing temperatures and fungi, sycamores still look quite bare. The only positive side of this situation is that the interesting bark characteristics of sycamores are easily viewed.

The browning of leaf tissue caused by the anthracnose fungus typically follows leaf veins, often forming a V-shaped brown lesion or dead spot. The fungus can also kill shoots, twigs, and branches. Year after year of shoot death can result in tufts of dead twigs forming throughout the tree.

Unfortunately, the fungus that causes anthracnose survives from year to year in specialized structures in the diseased twigs and shoots. When cool spring rains occur, the spores are released from these structures and are blown to newly forming leaves and shoots. Anthracnose does not typically kill trees. With the onset of hot and dry summer conditions, new leaves emerge and trees begin to fill out with foliage.

Fungicides are available to protect trees from the disease, but they are not usually economical or warranted in a home landscape situation. For further information on anthracnose diseases of shade trees and control measures, refer to the Iowa State University publication PM 1280 Anthracnose of Shade Trees. This bulletin is available through your Iowa State University county extension office or through the Iowa State University Extension Distribution Center by calling 515-294-5247.

Sycamore Leaf with Anthracnose

Sycamore leaf with anthracnose.
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