eXtension

oak tree mystery blob

Asked June 19, 2018, 6:07 PM EDT

A few days ago I noticed what looked like animal droppings. After noticing a lot more after the storm O looked up and noticed my two oak trees had these brown/black blob things on the braches. Today I went to Pahl's and brought one in and thought maybe caterpillars but they had no idea. I also cleaned up a target bag full from the yard. The trees seem to be in good condition. Hoping you can help diagnose and treat. I attached photos. Thank you!

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Dakota County Minnesota oak galls horticulture gouty oak gall

4 Responses

We can't be sure by viewing the photos, but we think the growths might be galls caused by a tiny wasp. Go here to learn more and see what you think:




Thank you for the quick response. One thing I question is that I’m not seeing any wasp around? Would they leave after hatching?
I would be open to having someone stop out to help me figure out a treatment

Most of the references we consulted indicate that there isn't a reliable control for the gall wasps. The wasps are tiny so you'd be unlikely to notice them. They lay their eggs in spring when the leaves are developing.

Learn about controlling the wasps here:


If the link to control information doesn't work properly, try copying the URL and pasting it into your browser.