pin oak tree disease - Knowledgebase Question

Saint Louis, Mi
Question by mcaewing
April 23, 2010
My pin oak tree has these brown cocoon like thing on the branches. They are are hard like a nut. the leaves are dying on the tree. What is this.

Answer from NGA
April 23, 2010


It sounds like a gall to me. Galls are abnormal growths or swellings on leaves, twigs, or branches. These deformities are caused by a tiny, non-stinging, wasp which produces a chemical that stimulates the plant to produce large, woody twig galls. Most galls are not pretty, but normally cause little damage to tree. If leaves are dying on the branch it might be that the gall has girdled the branch and the vascular system is clogged. If the leaves are not getting their share of moisture, they will die. For positive identification, why not cut off a stem or small branch with a gall attached and take it to your local cooperative extension? Helpful staff there can diagnose the problem and suggest control measures. Here's the address: St. Louis Extension Service, 724 North Union, St. Louis, MO 63108, phone 314-367-2585.

Best wishes with your pin oak!

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