Read on for resources grouped in the following categories: Best Management Practices for Nurseries; Guidelines for Restoration and Fieldwork; Resources from workshops, meetings, and mailings; and Resources by species: P. tentaculata and others.
Best Management Practices for Nurseries
- Guidelines to Minimize Phytophthora Pathogens in Restoration Nurseries (AKA “Nursery BMPs”) – The Phytophthoras in Native Habitats Work Group 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 March 2021)
- A sampling and diagnostic guide is under development; until a more formal publication is available, Phytosphere Research’s “leachate baiting” protocol may be useful to test for Phytophthora species in nursery container stock. Also see the updated How to construct a zoospore collection vessel (ZCV) – version 2 posted by Phytosphere.
- Frequently Asked Questions about the BMPs (updated August 2023)
- Buying healthy plants: What to look for at a nursery – guidelines created for the California Native Plant Society but useful to anyone wanting to work with plant growers on producing and purchasing healthy nursery stock. (Latest draft updated December 2017)
- Understanding results from the CDFA lab – a handout for nurseries
- Affordable Soil Heat Treating System: An example from The Watershed Nursery (video)
- Nursery Container Cleaning Instructions: An example from The Watershed Nursery (video)
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.
- “Restoration guidance” covers restoration site preparation and construction; guidelines for planting at field sites; procedures for sanitizing tools, surfaces, and footwear; and clean water specifications. (Also in Spanish)
- “Best Management Practices for Preventing Phytophthora Introduction and Spread: Trail Work, Construction, Soil Import” by Tedmund Swiecki and Elizabeth Bernhardt, Phytosphere Research, was written for the Golden Gate National Park Conservancy (January 2018). In 73 pages, it provides an introduction to Phytophthoras, a risk assessment model to determine which BMPs are needed under various conditions, as well as trail work, construction and soil import BMPs for use in sensitive habitat, known infested areas and park lands.
- “Guidance for contaminated or sensitive sites” is for restoration sites that has been confirmed to contain an Phytophthora infestation or are an especially sensitive habitat. (Also in Spanish)
- Guidelines for general construction in Spanish
- “Holding nursery guidance” presents a set of practices to avoid contamination of nursery stock being held for planting at restoration sites.
- “Guidance to reduce the risk of Phytophthora and other plant pathogen introductions to mitigation sites” (aka “Guidance for environmental regulators to reduce the risk of Phytophthoras and other plant pathogen introductions to restoration sites”) – this document is intended for professionals involved in regulating mitigation and restoration.
- “Start clean and stay clean when visiting native plant habitats” – this two-page handout provides guidance on how to reduce contaminated mud and plant materials from being transported to native plant habitats.
- “Come Clean Leave Clean” – This 3:11 minute video video from the California Invasive Plant Council was created in 2023 in collaboration with the Oakland Civicorps and Hip Hop for Change about site hygiene to reduce the spread of weed seeds and pathogens.
Resources from workshops, meetings & mailings
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. Also included are updates sent to our mailing list.
November 2023 vitrual CalPhytos meeting
Native Plant Buy-in Seminar. November 15, 2021 – Recording & Follow up Q&A
COMTF Virtual Annual Meeting, Day 3: CalPhytos meeting with presentations concerning Phytophthoras in restoration and natural areas (2 hrs). September 23, 2021 – Recording
Healthy Plants Forever After: the online meeting of the Phytophthoras in Native Habitats Work Group. June 30, 2020 – Recording
Tour of Sanitation Practices at Restoration Nurseries – Placerville. Placerville and Camino, CA; April 19, 2018 – Agenda
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 and Pot-washing station video
Phytophthora Species in Restoration Nurseries, Plantings, and Wildlands II. San Jose, CA; May 18, 2017
- Plant pathogen movement: updates from around the world – Susan Frankel, USDA-Forest Service, Pacific Southwest Research Station
- An update on Phytophthora species in California native plant nurseries – Suzanne Rooney Latham, CA Department of Food & Agriculture
- Phytophthora species in the field: life cycle, distribution, dispersal, impacts in California – Ted Swiecki, Phytosphere Research
- Managing Plant Pathogen Introductions in Large Scale Restoration Sites – Mia Ingolia, San Francisco Public Utilities Commission
- Santa Clara Valley Water District Case Study – Janell Hillman, Santa Clara Valley Water District
- Incorporating BMPs at a restoration nursery – Diana Benner, The Watershed Nursery
- The state of Phytophthora science: A view from the lab – Tyler Bourret, UC Davis
- The state of Phytophthora management: A view from the nursery – Jennifer Parke, Oregon State University
Implementing Phytophthora Sanitation Guidelines in Restoration Nurseries: A Field Workshop. Richmond, CA; March 1, 2017
- Guidelines to minimize Phytophthora species pathogens in restoration nurseries: rationale and review
- Nursery Case Study: Implementing the Guidelines to Minimize Phytophthora in Restoration Nurseries
- Field station photos
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
- Workshop agenda and speaker information
- The horticulture behind Phytophthora management
- Hands-on Irrigation Training
- Determining container physical properties worksheet
- Recognizing disease symptoms and sampling plants for the lab
- Examination & sampling for rotten roots and stems root diagram
- CDFA Protocol for Baiting the Root Ball in a Pot for Phytophthora spp.
- CDFA Flow Through Protocol for Baiting of potted plants to detect presence of Phytophthora spp.
- Video overview of hand-on stations
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)
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 aurantiacuss ubsp. 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. 01-2014Â Phytophthora tentaculata, November 2014
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)
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.
General Pathology Resources
Threats to oaks and other native plants from root-rotting Phytophthora species (handout by Dr. Tedmund J. Sweicki for the University of California Oak Health Virtual Workshop, April 2020)
Reid, A. (2006), Sampling and testing for plant pathogens. Department of Agriculture and Food, Western Australia, Perth. Bulletin 4683.
Resources for Regulators
Sample text from Santa Clara Valley Water District for General Project Conditions for Phytophthora and Phytophthoras and Nursery Stock. Posted January 2023.
