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Do you have any idea what this is on my oak tree? We are in the middle of a drought in Central Illinois and I've been seeing this on the back of my leaves.

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Sue Saddest Farewell TGO GL
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Kyle
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1 Answers1

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It'a a gall of some kind, though I couldn't tell you which species; I'd guess some species of the gall wasp Andricus.

Ed Staub
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