Ash Anthracnose Outbreak Affects Siouxland Trees

Ash trees around Siouxland are dropping their leaves. The leaf drop is likely due to anthracnose.  Anthracnose is a common fungal disease of trees in Iowa.  Woodbury County Extension office has received numerous calls this week from all over Siouxland about the problem. 
Anthracnose may occur on ash, sycamore, maple, oak, walnut and other deciduous trees. Cool, rainy weather in spring favors anthracnose development. Symptoms of anthracnose vary with the tree species. On ash, brown or black blotches typically appear on the leaflets. Affected leaflets often become distorted (they tend to curl toward the blighted areas) and fall from trees.
Fortunately, anthracnose does not cause serious harm to healthy, well established trees.  Cultural methods are the best way to control the disease. It is recommended to rake up and dispose of the fallen leaves, do not compost them.  Keep the tree healthy by making sure it gets the equivalent of one inch of rain or moisture by watering from a hose around the drip line of the tree.   
Since the problem is occurring early, the trees will have time to re-grow new leaves and recover.  Leaves that develop later in spring usually are not affected, as weather conditions are less favorable for anthracnose development. There is no need to apply a fungicide to affected trees.
For additional information, please contact ISU Extension-Woodbury County at (712) 276-2157.

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