Tuesday, March 15, 2011

Looking for Healthy American Elm Trees

Before elm populations were reduced by Dutch elm disease (DED), American elm (Ulmus americana) trees used to be dominant in many of the areas which are now dominated by ash trees. DED-tolerant American elm trees could be a good planting option for areas where ash is currently being impacted by emerald ash borer. There is a small plantation of elms in various stages of testing for DED tolerance. Several genotypes have been shown to tolerate DED, and a large portion of the progeny from crosses among these trees are DED-tolerant as well. The potential of seedlings from DED-tolerant crosses to be used for restoration plantings are currently being tested. It is hoped that large, stately American elm trees will someday grace American floodplain and swamp forests once again.
American elm trees, photo by Joseph O'Brien, USDA Forest Service, Bugwood.org

More DED-tolerant genotypes of American elm are currently needed for testing. The plan is to use them as parent trees for a plantation in order to have enough genetic diversity to use it as a seed orchard for large-scale plantings. Healthy American elm trees larger than 24 inches DBH (diameter at breast height) that are growing in areas that have had DED and that have not been treated with fungicides to prevent DED are needed. If you see a survivor elm that fits this description, please click here to enter its location and DBH at the USDA Forest Service Northern Research Station website.
All of the entries will be compiled in a database, prioritized for sampling, land owners contacted, and then small branches collected from the trees to propagate and test for DED-tolerance. Please forward to anyone who knows how to identify elm trees and might have interest in this project.