Are these galls on my pin oak?
I have these gross deformities on the ends of the branches on my 18 ye old, 30' tall pin oak. As best as I can identify them is galls. What should I do about them? Will they harm this tree and others? And why now? The mild winter?
Thanks for your question. Another Master Gardener has identified the cause of these galls as the Gnarled Oak Leaf Midge Gall. Here's a link to an Ohio State article about them, and another one from the Missouri Botanical Garden with the (limited) list of suggestions on how to deal with it. I hope these are helpful. Good luck!