Other Phytophthora species in California’s 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 Phytophthoras in Native Habitats Work Group formed to determine steps needed to protect wildlands and assist the restoration industry. The Work Group is now part of the California Oak Mortality Task Force and serves as an “Other Phytophthoras” committee for that group.

More information on Phytophthora detections in California native plant nurseries and restoration areas can be found below and is summarized in the following:

For more information on Phytophthora species that affect trees, visit the Forest Phytophthoras website.


Nursery Management Resources

Guidelines for Restoration and Fieldwork

Workshop Resources

Resources by species: P. tentaculata and others

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Nursery Management Resources

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Guidelines for Restoration and Fieldwork

These draft guidelines and best management practices (BMPs) aim to prevent and manage Phytophthora species during restoration activities and other field work, including trailwork and construction projects. This guidance is targeted for use in rare plant and other high-value habitats but may be applied to all areas where sustaining natural resources is a priority.

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Workshop resources

If you’ve attended one of our events, or just want to see what was covered, see below for more details and links to resources. Events are listed in reverse chronological order.

Tour of Sanitation Practices at Restoration Nurseries – Placerville. Placerville and Camino, CA; April 19, 2018 – Agenda and Photos

Joint meeting of the CNPS Ad-Hoc Committee and the Phytophthora Work Group. Los Angeles, CA. February 3, 2018 – Meeting summary

Tour of Sanitation Practices at Restoration Nurseries – San Francisco. San Francisco, CA; January 26, 2018  –  Photos

Tour of Sanitation Practices at Restoration Nurseries – South Bay/Peninsula. Palo Alto, CA; May 31, 2017  –  Photos    Pot-washing station video

Phytophthora Species in Restoration Nurseries, Plantings, and Wildlands II. San Jose, CA; May 18, 2017

Implementing Phytophthora Sanitation Guidelines in Restoration Nurseries: A Field Workshop. Richmond, CA; March 1, 2017

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

Managing Phytophthoras in Native Plant Nurseries: A hands-on workshop on prevention and early detection. Albany, CA; June 16, 2015

A systems approach to producing healthy container-grown plants: webinar with Dr. Jennifer Parke, Oregon State University. April 28, 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)

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Phytophthora resources by species

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.

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 Phytophthoras in Native Habitats Work Group

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