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.

More information can be found in the following:



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

May 18, 2017 – Phytophthora Species in Restoration Nurseries, Plantings, and Wildlands II, San Jose, CA. May 18 Symposium flyer; Register now!

May 31, 2017 – The nursery management tour continues, this time to the South Bay/Peninsula. More details coming soon!

See the entire calendar of Phytophthora-related events.


SB 287 – proposed CA legislation on Phytophthora pathogens in habitat restoration: Read the bill language and a fact sheet

Nursery Management Resources

  • Resources from “Implementing Phytophthora Sanitation Guidelines in Restoration Nurseries: A Field Workshop,” March 1, 2017


  • Affordable Soil Heat Treating System: An example from The Watershed Nursery (video)
  • Nursery Container Cleaning Instructions: An example from The Watershed Nursery (video)


  • 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 Phytophthora species 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
  • 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.

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

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