Testing and breeding DED-tolerant American elm

Researchers at the Northern Research Station would like to expand current efforts to screen American elm trees that may be tolerant or resistant to Dutch elm disease (DED). To facilitate this effort we are asking for the help of state foresters, park employees, and the interested public to identify large American elm trees on their landscapes.

Submit an American elm tree

Research Issue

Forestry Technician Stuart Mattix fastening a pollination bag on an American elm.

American elm trees, Ulmus americana, were widely distributed throughout the eastern United States before the arrival of Dutch elm disease (DED), caused by the fungal pathogens Ophiostoma ulmi and O. novo-ulmi. American elm was an important floodplain species and was commonly planted along city streets and boulevards because of its graceful form. Scientists have identified and bred fewer than a dozen American elm varieties that are tolerant enough of DED to survive to maturity after planting in forests and cities. Because the fungi that cause DED evolve genetically over time, additional DED-tolerant varieties of American elm are needed to ensure long-term survival of DED-tolerant elms.

Our Research

Our goal is to develop three separate genetically-diverse populations of DED-tolerant American elm trees that are adapted to growing conditions in New England, the lower mid-west, and the upper mid-west. We will use these trees to restore American elms in forests, towns and cities across the rural to urban gradient. To accomplish this, we are:

  1. Identifying large (2’+ diameter) survivor elms with strong natural tolerance to DED.
  2. Crossing these large survivors with other DED-tolerant American elm varieties in hopes that some of their offspring have multiple mechanisms for DED tolerance.

We test both the survivor elms and their offspring for tolerance to DED by injecting the DED fungus into the trees’ tissues. Trees that are not tolerant to the fungus will experience dieback in the crown (weak growth of leaves and eventual death of the twigs near the top of the tree) and will be removed from the program. Trees that show very low levels of crown dieback will be further tested for DED tolerance, and those with highest levels of tolerance will be kept in the breeding program.

Expected Outcomes

We are developing a generation of genetically diverse American elms that have strong tolerance to Dutch elm disease.

Research Results

Flower, Charles E.; Slavicek, James M.; Lesser, Dale; Eshita, Steven; Pinchot, Cornelia C. 2017. Canopy decline assessment in American elm after inoculation with different doses of Ophiostoma ulmi and O. novo-ulmi. In: Pinchot, Cornelia C.; Knight, Kathleen S.; Haugen, Linda M.; Flower, Charles E.; Slavicek, James M., eds. Proceedings of the American elm restoration workshop 2016; 2016 October 25-27; Lewis Center, OH. Gen. Tech. Rep. NRS-P-174. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station: 24-29.

Pinchot, C.C.; Flower, C.E.; Knight, K.S.; Marks, C.; Minocha, R.; Lesser, D.; Woeste, K.; Schaberg, P.G.; Baldwin, B.; Delatte, D.M.; Fox, T.D.; Hayes-Plazolles, N.; Held, B.; Lehtoma, K.; Long, S.; Mattix, S.; Sipes, A.; Slavicek, J.M. 2017. Development of new Dutch Elm disease-tolerant selections for restoration of the American Elm in urban and forested landscapes. In: Sniezko, Richard A.; Man, Gary; Hipkins, Valerie; Woeste, Keith; Gwaze, David; Kliejunas, John T.; McTeague, Brianna A., tech. cords. 2017. Gene conservation of tree species—banking on the future. Proceedings of a workshop. Gen. Tech. Rep. PNW-GTR-963. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station: 53-63.

Research Participants

Principal Investigators

Research Partners


  • Last modified: May 6, 2019