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Archived News Release from 2003

For Immediate Release

Ash and Sycamore Trees Hit by Fungus, Most Expected to Recover

Redwood City, CA - May 16, 2003 - Many Ash, Sycamore, and some other species of trees in Redwood City are looking very sickly this spring. These trees are not dead, but are being affected by a leaf, shoot, and twig blight disease called Anthracnose. City staff says that this is the worst occurrence of this disease that they have ever seen. It appears that the majority of the older leaves are infected this year and as a result, many of the trees appear to have few or no leaves.

The City does not spray for Anthracnose control, since fortunately the Ash and Sycamore trees are hearty and can generally withstand the defoliation caused by this disease. The problems associated with the disease are unattractive appearance, reduced growth, branch-tip dieback, and the need for raking additional leaves that have fallen as a result.

There are actually two benefits of the disease: the reduced leaf growth will slow the tree's overall growth and reduce the need for future pruning, and the typical leaf-attacking insect infestations, such as aphids, should be reduced.

The disease is caused by a fungus, and the severity of that fungus is dependent upon the spring weather. This year, the cooler moist spring weather around the time the leaf buds are opening has favored the spread of the fungus throughout the tree. The fungus resides in the older branches and twigs of the tree. Normally, the one-year old twigs that formed and grew in the previous growing season are not infected. However, the rains this spring may have spread the fungus to new growth located in lower parts of the tree. We typically expect the second and sometimes third new sets of leaves to be infected and drop.

Normally by August or September, the weather has remained hot and dry enough that the fungus is reduced and a set of leaves will remain on the trees for the remainder of the growing season. If you observe any other symptoms on your tree, please contact the City's tree maintenance staff for assistance by calling 650-780-7464.

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Bob Mullins
Urban Forestry Specialist

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