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Sudden Oak Death Agriculture

2015 Monitoring

Information for Master Gardeners


Water management for native plant nurseries

Many growers use water from an adjacent stream or river for irrigation. It is wise to treat this water before use, to prevent infection of crops with P. ramorum and other waterborne diseases. SammR300
Irrigating restoration plantings using stream water is risky if the plants are hosts and the water is contaminated. This is critical for Phytophthora spp. that cause root disease, such as P. lateralis and P. cinnamomi. While P. ramorum is not known to cause root disease, it can colonize the roots asymptomatically. The consequences of this is an area of research that needs further study. DSC02178_3530
Sediment deposited on plants after flooding is one means of transmitting P. ramorum inoculum from water to foliage. 350_sedimented plants
A high water table will create a flooded situation in an in-ground planting, increasing plant stress and potential for Phytophthora infection.


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350_high water table

Contact: Gary Chastagner, 253-445-4528 | WSU Puyallup Research & Extension Center, 2606 West Pioneer, Puyallup, WA, 98371-4998 USA
Last updated January 2, 2013



Pots should not be in contact with the soil, as diseases can both leave and enter through drainage holes. Insulate pots from the soil surface using one or all of these methods:
Weed cloth
300_ground covering 2
Fallen leaves and standing water + inoculum = Phytophthora infection 300_cans
Do not use dirty pots, they may contain inoculum. 300_dirty pots 2
If you re-use pots, be sure to clean residual soil and sanitize, using a dilute disinfectant solution, hot water, or steam.



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300_Pot wash station

Contact: Gary Chastagner, 253-445-4528 | WSU Puyallup Research & Extension Center, 2606 West Pioneer, Puyallup, WA, 98371-4998 USA
Last updated January 2, 2013


Soil and potting mix

This potting mix has been exposed to the elements and contains weeds and possibly diseases. It is important to store potting mixes in an area that is not in contact with the soil or where runoff water will infiltrate. 350_dirt pile 3
Cover the pile with a tarp or plastic to prevent contamination. 350pile covered
Or, even better, purchase clean potting soil from a reliable source.




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350_clean potting soil 2

Contact: Gary Chastagner, 253-445-4528 | WSU Puyallup Research & Extension Center, 2606 West Pioneer, Puyallup, WA, 98371-4998 USA
Last updated January 2, 2013

Symptoms of Phytopthora ramorum and look-alikes

Symptoms of Phytopthora ramorum and look-alikes

There are many diseases and pests that produce symptoms similar to those of Sudden Oak Death. This guide will help you to rule out SOD by identifying some of the more commonly encountered pest problems. In addition, it will help determine whether the plant is potentially infected with P. ramorum and the need for a sample to be collected.

On trees

Currently there are 5 tree species native to western North America that can be killed when they are infected with Phytophthora ramorum. These are tanoak (Lithocarpus densiflorus) and four oak species – Coast live oak (Quercus agrifolia), Canyon live oak (Q. chrysolepis), California black oak (Q. kelloggii), and Shreve oak (Q. parvula var. shrevei). In Europe, P. ramorum has been found to cause stem cankers leading to death of European beech (Fagus sylvatica), European sycamore (Acer pseudoplatanus), Horse chestnut (Aesculus hippocastanum), Northern red oak (Q. rubra), Sessile oak (Q. petraea), Southern beech (Nothofagus obliqua), Southern red oak (Q. falcata), and Turkey oak (Q. cerris). None of these tree species are native to Washington State, although they can be found planted as ornamentals. Some tree diseases that produce symptoms similar to P. ramorum are the following:

Armillaria root disease

Bacterial wetwood

Bleeding stem cankers

Phytophthora root disease and canker

On foliar hosts

Phytophthora ramorum produces leaf blotches, twig cankers, and shoot die-back on many plants. In some cases the shoot dieback may be severe enough to kill the plants (e.g., huckleberry and madrone), but in general they do not usually die as a result of P. ramorum infection. These are the most common hosts in Washington State. More will be added to the list as information becomes available.




Contact: Gary Chastagner, 253-445-4528 | WSU Puyallup Research & Extension Center, 2606 West Pioneer, Puyallup, WA, 98371-4998 USA
Last updated January 2, 2013



Use new containers for high risk host plant material to prevent contamination of plants from potting media and plant debris that may contain pathogens. smIMG_5447
Store used containers that previously had host material separately from those planned for re-use. smIMG_5460
Used containers from host and high risk plants should be recycled if they are not going to be sanitized. Re-using these containers introduces the risk of infection from residual soil and potting media containing disease inoculum. smIMG_5458
Used pots can be steam sterilized for re-use. This steam cabinet was constructed from materials available at most hardware stores and can be scaled to any size needed.The length of exposure to steam depends on the number of pots being sterilized. smIMG_5472
A hot water bath is used to sanitize small containers. Pots are stacked inside the plastic bin, which is lowered into the hot water bath and held for several minutes. Length of time in the bath depends on the number of pots being sanitized. smIMG_5488Back to Managing Phytophthora diseases in the nursery

Contact: Gary Chastagner, 253-445-4528 | WSU Puyallup Research & Extension Center, 2606 West Pioneer, Puyallup, WA, 98371-4998 USA
Last updated January 2, 2013

A Phytophthora tentaculata Pest Alert is now available!

A Phytophthora tentaculata Pest Alert is now available.  To date, P. tentaculata has been found infecting plants at three restoration sites – one in Monterey County and two in Alameda County.  It has not been found in the soil nor detected on adjacent native vegetation.  At the sites, the pathogen has been found on sticky monkey flower (Diplacus [=Mimulus]) and toyon (Heteromeles). Treatment, monitoring, and safeguarding at each location is ongoing to prevent spread.

Phytophthora tentaculata has also been found in five native plant nurseries to date in Butte, Monterey, Placer, and Santa Cruz Cos. on sticky monkey flower (Diplacus aurantiacus), toyon (Heteromeles arbutifolia), coffeeberry (Frangula californica), and Salvia mellifera. All infected plants were destroyed. Nearly 500 samples have been analyzed from native plant nurseries (voluntarily) as well as from additional restoration sites to test for pathogen presence.  In response to this situation, numerous native plant nurseries are now implementing best management practices, helping to insure that the best possible quality of plants are being grown. Surveys continue to determine if the pathogen occurs in undisturbed areas, particularly where the native plant nurseries have collected their propagative materials. These are the first detections of this Phytophthora in the US.  For more information, contact Kathy Kosta, CDFA, at

New Publications

Hansen, E.M. 2015. Phytophthora Species Emerging as Pathogens of Forest Trees. Current Forestry Reports. DOI: 10.1007/s40725-015-0007-7.

Species of Phytophthora are prominent in lists of emerging threats to forest ecosystems. We explore the conditions leading to and the consequences of the emergence of some Phytophthora species from their presumptive coevolved roles in undisturbed forest ecosystems to destructive agents as invasive forest pathogens. Phytophthora species are widespread, relatively abundant, very diverse, and poorly understood in many relatively undisturbed forest ecosystems. Three examples are examined in detail to illustrate the range of pathways to emergence and the varied consequences to forest environments. Phytophthora lateralis causes Port-Orford cedar root disease in western North America and now Europe. Phytophthora ramorum is causing unprecedented mortality in oak and tanoak forests in California, as the cause of sudden oak death, and is killing planted larch in the UK, and Phytophthora cinnamomi kills trees in parts of the world where it has been introduced. Active programs are underway in each case to manage, if not eliminate, their damage. In no case, however, has eradication been achieved. Prevention, by blocking initial introduction, has the highest probability of success.

Roy, B.A.; Alexander, H.M.; Davidson, J.; Campbell, F.T.; Burdon, J.J.; Sniezko, R.; and Brasier, C. 2014. Increasing Forest Loss Worldwide from Invasive Pests Requires New Trade Regulations. Frontiers in Ecology and the Environment. 12(8): 457–465.

Loss of forests due to non-native invasive pests (including insects, nematodes, and pathogens) is a global phenomenon with profound population, community, ecosystem, and economic impacts. We review the magnitude of pest-associated forest loss worldwide and discuss the major ecological and evolutionary causes and consequences of these invasions. After compiling and analyzing a dataset of pest invasions from 21 countries, we show that the number of forest pest invasions recorded for a given country has a significant positive relationship with trade (as indicated by gross domestic product) and is not associated with the amount of forested land within that country. We recommend revisions to existing international protocols for preventing pest entry and proliferation, including prohibiting shipments of non-essential plants and plant products unless quarantined. Because invasions often originate from taxa that are scientifically described only after their introduction, current phytosanitary regulations – which target specific, already named organisms – are ineffective.

Stream monitoring will be expanded in the Northern Olympic Peninsula, WA for Phytophthora ramorum

Northern Olympic Peninsula, WA Phytophthora ramorum stream monitoring will be expanded in spring 2015 in an effort to identify the source of inoculum contaminating the Dungeness River near Sequim, WA.  The river was found positive twice in 2013 and is not in the vicinity of a P. ramorum-positive nursery.  To date, follow-up sampling of streams in the area have not yielded information about the inoculum source.  The Chastagner lab at Washington State University, Puyallup will oversee the additional monitoring through a volunteer program and increase efforts to genotype isolates and DNA samples from waterways to help clarify the inoculum origin.  Several stormwater retention ponds in Pierce County will also be monitored to determine if landscaped areas in new developments may harbor the pathogen.