Disease can be transmitted in a nursery via used containers, which may harbor spores in potting media and plant debris. It is important to use clean containers for high risk host material, such as Rhododendron, Camellia, and Viburnum, to prevent infection of new plants.

• Recycle old containers and use new ones

  • “Plastic Nursery Pots – Greening Up The Darkest Side of Gardening” by Joe Lamp’l. Joe Gardener, May 2018.

  • “Pick your pot” Find out if container alternatives are right for your growing operation. Nursery Management March 2015
• Steam sterilization
  • “Hotter than ever” by Chris Guntermann. Digger Feb. 2009.
  • “Steam treating for weed control” by Whitney Rideout. American Nurseryman April 2012.
  • “Using a Steamroom to Sterilize Pallets of Styroblock™ Seedling Containers” by Andy Trent, Robert L. James,Clarke Fleege, and Gary Hileman. In: Riley, L. E.; Dumroese, R. K.; Landis, T. D., tech. coords. 2007. National proceedings: Forest and Conservation Nursery Associations—2006. Proc. RMRS-P-50. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. Online: http://www.rngr.net/nurseries/publications/proceedings
• Chemical sanitation – USDA approved methods
• Photos – Some ideas for container sanitation methods.
• Let us know if you have other ideas.

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Keep diseases out of your nursery by purchasing clean nursery stock from a trusted supplier. Monitoring incoming plant material is especially important in Washington since most is grown out of state.

Click here to see photos of situations involving plant material in nurseries.

Check plant material for disease symptoms before integrating it into the rest of the nursery stock using this guide to symptoms of Phytophthora ramorum and look-alikes on important PNW host plants.

High risk hosts in Washington are Rhododendron, Camellia, Viburnum, Pieris, and Kalmia species. Recently Vaccinium and Gaultheria spp. have been found with P. ramorum. These hosts are sold and planted in large quantities and have been connected to outbreaks of P. ramorum.

If you suspect P. ramorum on plant material, isolate it from other host plants. This key will help you determine the likelihood of P. ramorum infection. You can submit a sample to the WSU plant clinic for analysis.

Symptom ID and Scouting -Presentation from the Best Management Practices workshops in 2014

Click here to view the most recent APHIS list of regulated and associated hosts for P. ramorum.

Lists of certified shipping nurseries for the Pacific Northwest:

• Washington
• Oregon and California

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Many Phytophthora diseases, including P. ramorum, can survive and be transmitted in soil, potting media, and leaf litter. Good sanitation is important in reducing the amount of disease in the soil. Once the soil becomes infested with Phytophthora, it is very difficult to eradicate.

Photos – Management of soil and potting media, as well as sanitation techniques.

Sanitation for Nurseries -Presentation from the Best Management Practices workshops in 2014

USDA-APHIS approved methods for treatment and disinfection in nurseries (Appendix 8, Confirmed Nursery Protocol 2007)

Biosecurity measures for nurseries (Appendix 9, Confirmed Nursery Protocol 2007)

Articles

Shishkoff, N. 2007. Persistence of Phytophthora ramorum in soil mix and roots of nursery ornamentals. Plant Disease 91: 1245-1249.

Tjosvold, S. A., D. L. Chambers, E. J. Fichtner, S. T. Koike, S. R. Mori. 2009. Disease Risk of Potting Media Infested with Phytophthora ramorum Under Nursery Conditions. Plant Disease 93:4, 371-376

Steam boilers and soil steam sterilization systems. MSD AG (Möschle-Seifert-Dämpftechnik).

Steam Treating for Weed Control. Whitney Ridout, American Nurseryman 2012

Using heat to eradicate soil-borne plant pathogens from nursery potting media (“soil sterilization”). Elizabeth Bernhardt and Ted Swiecki, Phytosphere Research

Soil environmental factors and their relation to avocado root rot by John A. Menge and Lawrence J. Marais, Citrus Research Board

Back to Managing Phytophthora diseases in the nursery

Since Phytophthora diseases are waterborne, good water management practices are key in preventing plant losses.

Water management photos  – Examples of water management situations in nurseries in the Pacific Northwest.

Water Management for Nurseries -Presentation from the Best Management Practices workshops in 2014

Water Sampling Protocol (Appendix 7, Confirmed Nursery Protocol 2007)

The Water Education Alliance for Horticulture at the University of Florida has a comprehensive website on water management, mainly chemical and other treatments for water.

 Irrigation Pathogens and Water Quality – Learn how to recycle water without recycling pathogens at this Virginia Tech site.

A Short Introduction to Water Recycling for Plant Nurseries – this presentation provides a good summary of water treatments for nurseries, to prevent disease spread and reduce pollutant runoff.

Facts and Myths About Irrigation Water An overview of irrigation water treatments and uses in nurseries.

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