Brown Growth on Trunks of Gambel Oaks

Asked July 14, 2014, 11:19 AM EDT

I've noticed a section of scrub oak on my 5 acre property that has clumps of some kind of brown growth encircling the trunks and branches. It seems to be killing these trees slowly. I can't find anything on the internet about it, but am attaching photos.

Any advice you can give me about what this is and what I should do about it is appreciated.

Thank you!


El Paso County Colorado

5 Responses


Which county are you located? Just want to be able to route to the most appropriate person....Thanks! Ruth

El Paso. Thank you!

Thank you for your question and pictures.

When I try to magnify the picture it blurrs to the point that I cannot properly identify the culprit. HOWEVER it is a gall.

Gambel oak is native to Colorado and is adapted to most soil conditions in our state. Its typical form is a multi-stemmed shrub but can become tree-like with additional water.

Oaks are generally pest free. Galls, or round protrusions on leaves or stems, are unsightly but do not harm the trees. No control measures are recommended.

If you would like to confirm this is nothing serious, please take a sample into your El Paso County Master Gardener Help Desk and they will put the gall under the microscope and take a closer look. They will need a 16 inch branch with healthy growth and also one that has a gall attached.

They are located at 17 N. Spruce Street, 2nd Floor. Open 9-noon, M-F.

Thank you so much, Kerry!


In doing some additional research, it may be a canker. I would recommend taking a sample into the Help Desk. I am going to research a bit more, but without a clear picture (close up) it is difficult to diagnose.

Thank you again.