Welcome to CalPhytos.org – Phytophthoras in Native Habitats

Photo by Janell Hillman, Santa Clara Valley Water District


Several first-in-the-USA detections and newly identified species of Phytophthora in both native plant nurseries and restoration areas have occurred in recent years. Many of these Phytophthora species appear to have wide host ranges, capable of causing disease on plants across many families and in many different habitats. The Working Group for Phytophthoras in Native Habitats has formed to determine steps needed to protect wildlands and assist the restoration industry.

Read more in “In BriefPhytophthora plant pathogens in California native plant nurseries and habitats. Why the concern?” (May 2015) and in the links below.


Nursery Management Resources

Guidelines for Restoration Activities

Resources by species: P. tentaculata and others

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Working Group for Phytophthoras in Native Habitats

Calendar of Events

12/6 – 12/8 – 7th Western Native Plant Conference; Vancouver, WA

Jennifer Parke and Marianne Elliott will be presenting “Phytophthora diseases in native plant production: why should I care and what can I do about it?”

For more information and to register online, go to: http://westernforestry.org/upcoming-conferences/seventh-western-native-plant-conference.

12/14 – Preventing Phytophthora Contamination in Native Plant Nurseries; North Willamette Research and Extension Center (NWREC); Aurora, Oregon; 9am – 1pm; Register online at: https://www.bentonswcd.org/activities/calendar/annual-events/phytophthora-workshop/; For more information contact (541) 753-7208.

See the entire calendar of Phytophthora-related events.


CNPS is supporting clean nursery practices – see the article in the CNPS Bulletin, volume 46, issue 2 (April-June 2016).

UK nurseries are getting involved in a “Keep It Clean” campaign for Phytophthoras, as described in a recent Horticulture Week article.

Nursery Management Resources

Guidelines to Minimize Phytophthora Pathogens in Restoration Nurseries – The Working Group for Phytophthoras in Native Habitats complied these guidelines to help design and maintain a nursery system that excludes Phytophthora and other plant pathogens to the best extent possible. These are intended for professional nursery growers that supply plants to wildland restoration projects. (Latest draft updated September 22, 2016)

Understanding results from the CDFA lab – a handout for nurseries

A systems approach to producing healthy container-grown plants: webinar with Dr. Jennifer Parke, Oregon State University. April 28, 2015. See all online resources and view a recording at http://uc-d.adobeconnect.com/r91g3to9726/.

Resources from the “Managing Phytophthoras in Native Plant Nurseries: A hands-on workshop on prevention and early detection,” June 16, 2015

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Guidelines for Restoration Activities

These draft guidelines were developed to prevent and manage Phytophthoras during various aspects of restoration. This guidance is targeted for use in rare plant and other high-value habitats.

  • Restoration guidance” covers General Construction; Guidelines for Planting at Field Sites; Procedures for sanitizing tools, surfaces, and footwear; and Clean water specifications.
  • Contaminated site guidance” is for restoration sites that has been confirmed to contain an Phytophthora infestation.
  • Holding nursery guidance” presents a set of practices to avoid contamination of nursery stock being held for planting at restoration sites.

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Phytophthora resources by species

General information

Concerns Over Plant Pathogen Introductions in Native Plant Nurseries and Restoration Sites. California Department of Fish & Wildlife Conservation Lecture, April 2016

Presentations from the Do No Harm Restoration workshop, Palm Desert, November 2015

Exotic Phytophthora Species in Native Plant Nurseries, Restoration Plantings, and Wildlands, video recording. Courtesy of the Central California Native Plant Nursery Network, December 2, 2014

  • Plant pathogen movement: around the world on planting stock – Susan Frankel, USDA-Forest Service, Pacific Southwest Research Station (http://youtu.be/KZAlexLWNGY)
  •  Phytophthora species: life cycle, distribution, dispersal, impacts in California – Ted Swiecki, Phytosphere Research (http://youtu.be/lMw4NpDgCTs)
  • P. tentaculata: History, Host Range, and Status in California Nurseries – Suzanne Rooney Latham, CDFA (http://youtu.be/HK4-NMsDbm8)
  •  Best Management Practices to minimize the risk of Phytophthora and other pests and pathogen introductions into nurseries – Kathy Kosta, CDFA (http://youtu.be/oKEQqDBU3vw)
  •  Systems approach to Phytophthoras in nurseries – Karen Suslow, NORS-DUC (http://youtu.be/CuPYc9lcCcc)
  •  Phytophthora Effects on Native Habitat Restoration – Greg Lyman, SF Public Utilities Commission (http://youtu.be/ypRe4nX6fSo)
  •  Case Study: Incorporating CDFA BMPs at a restoration nursery – Diana Benner, The Watershed Nursery (http://youtu.be/7AEnZp2-_14)
Phytophthora tentaculata

Phytophthora tentaculata was initially detected in a native plant nursery causing a severe root and crown rot in sticky monkey flower, Diplacus aurantiacus subsp. aurantiacus (Scrophulariaceae) in 2012. Since then it has been detected in several nurseries and a few restoration sites where outplanted stock was found to be infected.
CDFA Plant host list for Phytophthora tentaculata, February 2016

USDA Phytophthora tentaculata Pest Alert, February 2015

CDFA Nursery Advisory No. 01-2014 Phytophthora tentaculata, November 2014

2010 APHIS New Pest Response Guidelines, “Phytophthora species in the Environment and Nursery Settings.” Includes Phytophthora tentaculata literature review and pictures of the pathogen in culture.

Rooney-Latham, Suzanne; Cheryl Blomquist; Ted Swiecki; Elizabeth Bernhardt. 2015. Phytophthora tentaculata. Forest Phytophthoras 5(1). doi10.5399/osu/fp.5.1.3727. A compendium of information on Phytophthora tentaculata that includes photographs of field symptoms, a table of known hosts and more, geared to a technical audience and containing many photomicrographs. (PDF for download) http://journals.library.oregonstate.edu/index.php/ForestPhytophthora/article/view/3760/3652

Rooney-Latham, S., C. L. Blomquist, T. Swiecki, E. Bernhardt, and S. J. Frankel. 2015. First detection in the US: new plant pathogen, Phytophthora tentaculata, in native plant nurseries and restoration sites in California. Native Plants Journal 16:(1) 23-27. Abstract: Phytophthora tentaculata Kröber & Marwitz (Pythiaceae) has been detected in several native plant nurseries in 4 California counties and in restoration sites on orange sticky monkey flower (Diplacus aurantiacus (W. Curtis) Jeps. subsp. aurantiacus [Scrophulariaceae]), toyon (Heteromeles arbutifolia (Lindl.) M. Roem. [Rosaceae]), coffeeberry (Frangula californica (Eschsch.) A. Gray [Rhamnaceae]), and sage (Salvia spp. L. [Lamiaceae]). These findings are the first detections of P. tentaculata in the US and the first ever on these host plants. Phytophthora species are a known problem in horticultural nurseries, but little attention has been placed on native plant or restoration nurseries. The potential for plant pathogens to be outplanted along with native plant nursery stock is very high, posing a threat to neighboring forests. http://npj.uwpress.org/content/16/1/23.abstract.

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The Working Group for Phytophthoras in Native Habitats

Mission Statement (draft as of November 2015)

Working Group Organizational Chart (draft as of January 2016)

Contact Janice Alexander for more details on how you can be involved with the Working Group.