Identification of peony diseases in the Pacific Northwest and Alaska

Project Overview

Project Type: Graduate Student
Funds awarded in 2016: $24,979.00
Projected End Date: 01/31/2018
Grant Recipient: Washington State University
Region: Western
State: Washington
Graduate Student:
Principal Investigator:
Gary Chastagner
Washington State University

Annual Reports

Information Products


  • Additional Plants: ornamentals


  • Education and Training: extension, workshop
  • Pest Management: chemical control, cultural control, disease vectors, eradication, field monitoring/scouting, integrated pest management, physical control, prevention, sanitation

    Proposal abstract:

    Little research has been done to diagnose the causal agents of various diseases that affect peony. Modern extension bulletins and growers’ guides rely on nearly 100 year-old research to diagnose disease on this high-value cut flower and landscape crop. Through our current efforts focused on identifying species of Botrytis on peony, it has become increasingly clear that the current literature surrounding peony pathogens is inadequate. Our limited sampling of peony pathogens has identified the existence of two pathogens not previously reported in the United States. These and several species of Botrytis are new to peony or newly discovered. While peonies have historically been a small-acreage crop, a surge of growth in production has been observed in the western United States, especially in Alaska where the cut peony flowers are being produced at a time of year when no other country in the world is able to harvest this crop due to differences in environmental conditions. As a result, peonies are becoming a major economic force in the state of Alaska with over 1,000,000 stems projected to sell in 2015. Alaskan-grown peonies sell for $2 to $6 per stem, making peonies a multi-million dollar industry for Alaska. In 2012, over 100,000 roots were in production in Alaska and those numbers are continually growing. Many Alaskan growers are sourcing this peony rootstock material from farms located in Washington and Oregon; thus, multiple Pacific Northwest farmers are being impacted by Alaska’s increasing production. Through our discussions with farmers, it has become clear that both cut flower and rootstock producers are in need of knowledge and education about the pathogens that cause disease on their crops in order to maintain the vitality of this emerging industry.  We proposed a project to survey for and identify causal agents of various peony diseases throughout the Western region of the United States, as well as in other economically-important and informative peony producing states. A survey of samples, both from our own farm site visits as well as those obtained from peony growers, will elucidate not only the different pathogens infecting peony, but also the frequency at which they occur in each of the peony-producing regions. We propose using the collected information to produce an updated growers’ guide in the form of an extension bulletin for easy-access to growers and to hold hands-on grower education training through many of the pre-established networks we have formed both in Alaska and Washington. Lastly, our project will produce first reports in the journal Plant Disease of these pathogens as they are not only the best way for pathogen existence to become accessible knowledge, but also because first reports on ornamental crops, while seemingly small, have potential for enormous local impact.

    Project objectives from proposal:

    Objective 1. During the spring and summer of 2016 we will conduct surveys to obtain diseased foliage and solicit additional foliage to be collected by peony growers. Collections will focus on at least 30 growers in Alaska, Oregon, and Washington; however, they will extend to other Western states as identified during the course of the study.


    Objective 2. We will attempt to isolate causal organism of disease using traditional fungal and bacterial isolation methods. The isolated organisms will be maintained in-vitro in petri plates containing the appropriate growth media.


    Objective 3. We will use a combination of morphological and molecular methods (PCR and sequencing) to positively identify the suspected causal organisms of disease. If suspected pathogen is viral, samples will be submitted to a commercial virus screening laboratory for identification.


    Objective 4. We will perform Koch’s postulates on live plants and detached peony tissues to determine pathogenicity of the organisms. 


    Objective 5. We will prepare and disseminate information regarding the peony pathogens. Such educational material will include an extension bulletin published through Washington State University and/or the University of Alaska Fairbanks, a workshop conducted in Alaska, and first reports published in peer-reviewed journals. 

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.