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National Elm Trial Ornamental Plant Pathology

National Elm Trial at WSU Puyallup

Introduction

The National Elm Trial is a volunteer effort to evaluate and promote the use of Dutch elm disease (DED)-resistant American and hybrid elms.

This nation-wide study has one coordinating and reporting system that is based at Colorado State University. The effort grew out of the NCR-193 Agricultural Experiment Station coordinating committee on insects and diseases of woody ornamentals, a group of researchers and extension specialists from land grant universities around the United States.

The National Elm Trial includes between 15-18 DED-resistant and commercially available elm cultivars planted at seventeen sites in sixteen states. These elm cultivars will be evaluated over a wide range of growing conditions and hardiness zones.

National Elm Trial

It is important to maximize the genetic diversity of shade trees within the nation’s urban forests because of the increasing threat of exotic pest and pathogens.

The American Elm is an example of a species that once dominated urban forests across the US, but has essentially disappeared because of the introduction of Dutch elm disease. This loss has stimulated research to select and breed DED-resistant cultivars, but the performance (e.g. growth and tolerance to other pests and pathogens) of these cultivars need to be studied further to identify the best fit cultivars for each region.

Therefore, the overall goal of the National Elm Trial is to compare the performance of DED-resistant cultivars across a wide range of growing conditions.

More specific objectives of the study are to:

  1. Determine the growth and horticultural performance of commercially available DED-resistant elm cultivars in various climate regimes in the United States.
  2. Determine the relative disease, insect, and abiotic stress tolerance of these cultivars.
  3. Promote the propagation and use of elms through local, regional, and national reporting of the trial results to wholesale tree propagators and growers, retail nursery and garden center operators, landscaper designers, arborists, and the general public.

More information about the project and all the sites involved is available on the National Elm Trial main site.

Research Outcomes

National Elm Trial planting at WSU Puyallup