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WSU Puyallup Ornamental Plant Pathology

Christmas Tree Research Program


The Pacific Northwest produces close to one third of the Christmas trees sold each year nationally.

The goal of our research program is to provide growers and retailers with research-based information that creates a high-quality Christmas tree products for consumers. We strive to accomplish this goal by conducting applied research focused on reducing the impacts of pests and pathogens and increasing the longevity of trees after they are harvested.


Much of our pest and disease research has focused on:

  • the development and management of Annosus root rot,
  • the development of effective ways to reduce populations of insects on trees that restrict export markets,
  • and the identification of sources of trees with resistance to common diseases and insect pests such as:
    • Phytophthora root rot,
    • current season needle necrosis,
    • Grovesiellia canker,
    • spider mites,
    • and twig aphids.

Our postharvest research has focused on the identification of sources of true firs that have superior needle retention by testing detached branches.

Publications and Reports

  1. A Survey of Phytophthora spp. Associated with Abies in U.S. Christmas Tree Farms. K. M. McKeever and G. A. Chastagner, Plant Disease 2016 100:6, 1161-1169
  2. Postharvest Quality of Noble and Nordmann Fir Christmas Trees. G. A. Chastagner and K. L. Riley, American Society for Horticultural Science, 2003: 38:3.
  3. The Christmas Tree: Traditions, Production, and Diseases. G. A. Chastagner and M. D. Benson, Plant Health Progress 2000 1:1
  4. Christmas Tree Diseases, Insects, and Disorders In The Pacific Northwest: Identification and Management.1997. WSU Extension Publication MISC0186.

Contact: Gary Chastagner, 253-445-4528 | WSU Puyallup Research & Extension Center, 2606 West Pioneer, Puyallup, WA, 98371-4998 USA