Plant and Insect Diagnostic Clinic Update - June 16, 2008

The past few weeks we have been receiving many samples of anthracnose, a group of fungal diseases favored by cool wet conditions. Anthracnose can affect many shade trees, but we have been getting most reports from ash and maple. Anthracnose will cause irregularly shaped and and sized brown spots on the leaves of maple. On ash, anthracnose large brown blotches, and often causes the leaves of ash to fall. The good news is that anthracnose-defoliated trees almost always replace the lost leaves within a few weeks. Anthracnose is not usually harmful to a well established tree, and we do not generally recommend fungicide control. Please see the pamphlet Anthracnose of Shade Trees.

We have received several ash samples with ash rust, it is another disease favored by cool wet weather, but is usually not harmful to a healthy tree. Please see this article from June 14, 2006 HHPN on ash rust.

We are also receiving many samples of trees with problems related to water logged soils. Please see the article in this issue about flooding effects on many plants, fruits and vegetables and the pamphlet Understanding the Effects of Flooding on Trees.

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