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Maple Leaf Blister: Black Leaves on Maple Explained
This article was published originally on 6/3/2009
A foliar disease called leaf blister has been common on silver and red maples and their hybrids during the past few weeks. The causal agent is the fungus Taphrina carveri. The disease may go unnoticed until a large number of leaves are severely infected and begin to fall from the tree. Symptoms include grayish brown-to-black irregularly-shaped, slightly-raised but not always obvious blisters on the leaves. The leaf blisters turn black, often lighter-colored in the center. (Fig. 1) Multiple infections will cause the leaf to become distorted. (Fig. 2) The rounded shape of the spots and blistering distinguish this disease from maple anthracnose, which produces irregularly shaped brown spots or blotches that follow the veins of leaves and is caused by a different fungus. Leaf blister and anthracnose can occur on the same tree and even on the same leaf.