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Northern Research Station
11 Campus Blvd., Suite 200
Newtown Square, PA 19073
(610) 557-4017
(610) 557-4132 TTY/TDD

Dutch Elm Disease

Restoration of the American Elm in Ohio and the Eastern United States

Research Issue

[photo] At the Mohican Memorial State Forest, American elms at the time of planting in 2003.The Northern Research Station (NRS) initiated the American Elm Restoration Project (AERP) in 2003 to restore the American elm in Ohio.  American elm tree strains with high levels of tolerance to Dutch elm disease (DED) were established in areas where the trees can naturally regenerate and spread.  The process of regeneration will allow the American elm to co-evolve with the DED fungal pathogen, ensuring that this valuable tree species will not be lost from the landscape.  This effort is being carried out in partnership with the Ohio Department of Natural Resources Division of Forestry, Franklin County Metro Parks, and The Wilds.  The NRS expanded this project in 2005 to sites in Iowa, Wisconsin, and Minnesota in partnership with Northeastern Area State and Private Forestry, Luther College (Iowa), the U.S. Army Corps of Engineers, and the Carpenter St. Croix Valley Nature Center (Minnesota).  In 2007, a site was established at Dago Slough near Cassville (Wiconsin) in partnership with the U.S. Fish & Wildlife Service, and a test planting was established at the Bad River Indian Reservation (Wisconsin) to assess tree cold hardiness.  Three additional sites were established in Vermont in 2010 in partnership with The Nature Conservancy.

Our Research

History of the American elm

[photo] Mohican Memorial State Forest American elm restoration site in 2006.The American elm was once widely distributed throughout the eastern United States and was preferred for planting along city streets and in the yards of many homeowners. The Dutch elm disease fungal pathogen Ophiostoma ulmi was introduced into the United States in 1930 and in the subsequent years has destroyed millions of American elm trees all over the United States and Canada. By 1976 only 34 million of the estimated 77 million elms present in urban locations before introduction of the DED pathogen remained, and far fewer are still present today. The American elm’s height and vase-like shape provides for a uniquely graceful tree. The crowns of mature elms would span roadways, houses, and park recreation areas and provide the benefits of cleaner air and cooler temperatures. The American elm is one of few trees capable of growing relatively well within the harsh urban environment of high summer temperatures, air pollution, and road salt present in northern latitudes. Research on the American elm since the 1970s has focused on identifying American elms that could withstand the DED pathogen. Over 100,000 American elm trees were tested for resistance to Dutch elm disease. No resistent trees were found. However, a few exhibited good levels of tolerance to the disease. A resistant tree shows no DED symptoms after injection of the fungus, whereas a tolerant tree shows disease symptoms the year of inoculation but no symptoms the next year. Some branches die after fungal injection but are replaced after a couple of years. Only five trees were identified that exhibit the necessary levels of DED tolerance to withstand the disease and they are used for the restoration effort.

Retention of the American elm into the future

[photo] Mohican Memorial State Forest American elm at restoration site in 2010; it has grown taller than a 24 foot pole.The identification of DED-tolerant American elms allows for the reintroduction of the American elm into urban areas. However, no effort is currently underway to restore these elms into forested landscapes. In addition, and most importantly, only two individual American elm selections are being used to reintroduce the elm into urban landscapes. Unfortunately, if the DED fungus mutates to a form that can overcome the tolerance mechanism in these two elm selections, the disease will once again kill American elms. It’s not a matter of whether this will occur but when, since the DED fungus will continue to evolve while street trees will not since they do not propagate themselves. The American elm forest restoration project will allow the most DED-tolerant American elm trees identified to date to propagate, evolve, and develop mechanisms that can withstand new forms of the DED fungus. This project will ensure the retention of the American elm in forested landscapes and provide future trees that are tolerant to new forms of DED. In addition, as new DED tolerant elm selections are identified, they will be added to the existing restoration sites to increase genetic diversity.

Establishment of American elm restoration Sites:

The AERP sites in Ohio were established in 2003, 2004, and 2009. The sites at Luther College, Stoddard Islands, and the Carpenter St. Croix Valley Nature Center were established in June 2005; the Dago Slough site in May 2007; the test planting at the Bad River Indian Reservation in May 2007, and the Vermont sites in June 2010.

Research Results

Slavicek, James M. 2007. Expansion of the American elm restoration effort to the upper Midwest. In: Gottschalk, K. W., ed. Proceedings, 17th U.S. Department of Agriculture interagency research forum on gypsy moth and other invasive species, 2006.; Gen. Tech. Rep. NRS-P-10. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station: 90.

Slavicek, James M.; Boose, Andrew; Balser, Dan; Cavender, Nicole 2005. Restoration of the American Elm in Forested Landscapes. In: Gottschalk, K. W., ed. Proceedings, 16th U.S. Department of Agriculture interagency research forum on gypsy moth and other invasive species, 2005. Gen. Tech. Rep. NE-337. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northeastern Research Station: 74.

Research Participants

Principal Investigator

  • James Slavicek, Research Biologist, U.S. Forest Service, Northern Research Station

Research Partners

  • Linda Haugen, Plant Pathologist, U.S. Forest Service, Northeastern Area State and Private Forestry Dan Balser, Ohio Division of Natural Resources, Division of Forestry
  • Andrew Boose, Metro Parks, Westerville, Ohio
  • Nicole Cavender, The Wilds, Cumberland, Ohio
  • Rich Tenneson, Luther College, Decorah, Iowa
  • Randy Urich and John Sobiech, U.S. Army Corps of Engineers, Natural Resource Project, LaCrescent, Minnesota
  • John McPherson, Horticulturist, Carpenter St. Croix Valley Nature Center, Hastings, Minnesota
  • Richard Kittelson, Northeast Iowa Resource Conservation and Development Inc, Postville, Iowa
  • Tim Yager, U.S. Fish and Wildlife Service
  • Christian Marks, The Nature Conservancy, Connecticut River Program
  • Scott Brown, Parks Department, Worthington, Ohio

Last Modified: 10/14/2010