Question of the Week #1: August 25, 2016
It’s pretty disgusting looking, but to the plant it’s even worse than that. This is crown gall of roses.
“Neil, what is this ugly growth on my rose bush? What should I do?”
Most people who garden a good bit will eventually encounter a plant with crown gall. It’s the result of a bacterium that has either been with the plant since it was in the nursery, or that has entered through a wound.
The short answer is that there is no prevention or cure. Infected plants should be removed carefully, taking pains not to touch the infected plant and then healthy plants in that order, either with tools or with your hands. You should do your best to remove all the roots of the infected plant. Do not replant in that same area with the same type of plant or any other susceptible species for several years.
Here is another photo of crown gall from the Plant Pathology website of Iowa State University. Photo was by Bob Dodds.
Here are two very good write-ups on crown gall, first from Iowa State and then from the Texas Plant Disease Handbook from Texas A&M.