how to kill cottonwood roots after tree is gone and stump is ground out
We purchased a vacation home in Sedona (185 Mission Road, Sedona AZ 86336) on May of this year. Our main residence is in Minneapolis. We have just become aware of problems at Mission Rd (roots totally blocking buried down spout extension pipes; suspected invasion of plumbing lines to a small [below ground] pool and/or hot tub, or possible crack in pooland/or hot tub; new suckers popping up everywhere in the yard) with the still viable cottonwood roots from a super large cottonwood tree (that we never saw, but was taken down by the previous owner maybe a year or so ago). We want to permanently kill the roots, but I have been told by 2 Arizona tree services that excavation of the entire yard (to dig out the roots) is my only answer now, because the stump was not left above ground, available to be chemically treated. Please contact me at 612 600-4115 or janedemay@Q.com and I will give you the full story. The big question: is there any way to chemically treat these roots now? I'm hoping for better news from you!!
Thank you for your question for eXtension. I am afraid that I have no encouraging news on the cottonwood suckering problem you are describing. If you allow some of the sprouts to grow, these could be treated with a cut stump application of herbicide, but small stems are not the best because they cannot translocate the quantity of herbicide necessary to kill the large root ball. Some people have used black plastic sheets to exclude sunlight from the sprouts. This may be possible, but it depends on the size and scope of the sprouting area. You might try treating the sprouts this spring with tryclopyr or glyphosate (as outlined in the linked publication). This would be most effective in September or October. Here is the link: http://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1401.pdf. You may contact our offices directly in the future - here is our website: http://extension.arizona.edu/yavapai.