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WSU Puyallup Ornamental Plant Pathology

Crowdfunding to start a forest pathology focused citizen science program in South Africa

See below for information about this exciting new citizen science program


My name is Joey Hulbert and I am a forest pathologist in training. I recently completed a MS at Oregon State University and now I am  prepping to move to South Africa for a PhD with Dr. Micahel Wingfield at FABI.

For the PhD, we plan to survey the indigenous forests of South Africa for Phytopthora species with the help of the public. We want to create a citizen science program that teaches the public about forest pathology and invites them to help sample the trees in their communities and near-by forests. The PhD will be funded but we are trying to raise support for starting the citizen science program. To do this we have launched a crowdfunding campaign.
I am reaching out to you with hope that you will share this project with your social networks and anyone who may see the value in this project. Please help us spread the word!
The below link will take you to the project. There is a 5-minute video that I put together to summarize the scope and value.

Discovering plant destroyers in South Africa


National Elm Trial at WSU Puyallup

National Elm Trial at WSU Puyallup


It is important to maximize the genetic diversity of shade trees within the nation’s urban forests because of the increasing threat of exotic pest and pathogens.

The loss of elms to Dutch Elm Disease (DED) has stimulated research to select and breed DED-resistant cultivars, but the performance (e.g. growth and tolerance to other pests and pathogens) of these cultivars need to be studied further to identify the best fit cultivars for each region.

Therefore, the overall goal of the National Elm Trial is to compare the performance of DED-resistant cultivars across a wide range of growing conditions.

About Elms

Valley Forge cultivar

The American Elm is an example of a species that once dominated urban forests across the US, but has essentially disappeared because of the introduction of Dutch Elm Disease.

Dutch Elm Disease

Elm trees in the United States are threatened by DED. The disease has already killed between 30-50 million elm trees throughout the UK (Brasier). Reports in North America range back to the 1920s, but its presence in Washington was not confirmed until 1978 (Maloy and Inglis 1978).

More information about the history, biology and control of DED is available in the Pacific Northwest Pest Management Handbook.

Pruning Elms

You can find guidelines and recommendations for pruning elms on this page.

Additional pruning guidelines are available in the Pruning instructions for elms (PDF) shared by J. Frank Schmidt & Son Co. 2004

National Elm Trial

The National Elm Trial is a volunteer effort to evaluate and promote the use of Dutch elm disease (DED)-resistant American and hybrid elms.

This nation-wide study has one coordinating and reporting system that is based at Colorado State University. The effort grew out of the NCR-193 Agricultural Experiment Station coordinating committee on insects and diseases of woody ornamentals, a group of researchers and extension specialists from land grant universities around the United States.

The National Elm Trial includes between 15-18 DED-resistant and commercially available elm cultivars planted at seventeen sites in sixteen states. These elm cultivars will be evaluated over a wide range of growing conditions and hardiness zones.

More information about the cultivars used in the National Elm Trial is available in a PDF Table here.

The specific objectives of the National Elm Trial are to:

  1. Determine the growth and horticultural performance of commercially available DED-resistant elm cultivars in various climate regimes in the United States.
  2. Determine the relative disease, insect, and abiotic stress tolerance of these cultivars.
  3. Promote the propagation and use of elms through local, regional, and national reporting of the trial results to wholesale tree propagators and growers, retail nursery and garden center operators, landscaper designers, arborists, and the general public.

More information about the project and all the sites involved is available on the National Elm Trial main site.

Research Outcomes


Resources & Publications

National Elm Trial planting at WSU Puyallup

Influence of Nitrogen Fertility

Nursery research

Influence of Nitrogen Fertility on the Susceptibility of Rhododendrons to Phytophthora ramorumDSC06123 rhody

Rita L. Hummel, Marianne Elliott, Gary Chastagner, Robert E. Riley, Kathy Riley, and Annie DeBauw, Washington State University, Puyallup Research and Extension Center, 2606 W. Pioneer, Puyallup, WA 98371;

Research information demonstrating the effects of various cultural practices on host susceptibility to Phytophthora  ramorum is generally lacking and thus limits the development of an integrated approach to managing diseases caused by this pathogen in irrigated nursery systems.  Rhododendron spp. have accounted for about 78% of the plants associated with P. ramorum-positive nursery finds in Washington State. Nitrogen fertility levels have been reported to influence disease in some Phytophthora disease pathosystems, but data is not available for the P. ramorum-rhododendron pathosystem.

During 2008 we investigated the dynamics between nitrogen application rates and the susceptibility of ‘English Roseum’, ‘Cunningham’s White’ and ‘Compact P.J.M.’ to P. ramorum.  One-gallon plants were potted into 3-gallon containers.  The growing medium was 100% Douglas-fir bark with micromax incorporated at the rate of 1.75 lbs/yd3. Plants were placed on a gravel nursery bed and watered as needed with overhead sprinkler irrigation.  Residual fertilizer in the media was depleted, then ammonium nitrate fertilizer at 100, 300 and 600 ppm N was applied in liquid form twice a week to each of eight plants per cultivar starting on June 2nd.  The same rate of P (potassium phosphate) and K (potassium sulfate), 100 and 200 ppm, respectively, was applied at each fertilization.  Commencing with fertilizer application, the plants were switched to a drip irrigation system.  In early October, plant growth, visual quality and leaf color were measured. At the same time, fully mature, current season leaves from each plant were harvested for determination of leaf tissue nitrogen content and P. ramorum inoculations.

Six detached leaves from each plant were inoculated with suspensions of zoospores from an NA1 lineage rhododendron isolate of P. ramorum by pipetting a 10 ul drop of suspension onto the lower leaf surface. The leaf tissue beneath drops on three leaves was injured using an insect pin, while the tissue beneath each drop on the other leaves was left unwounded. The leaves were then incubated at 19-20 C.

As expected, shoot growth and plant quality indices increased with nitrogen fertility. Based on an overall analysis of lesion size after 10 days, there was a significant difference in the susceptibility of the three cultivars to P. ramorum. “Compact P.J.M.’ had the smallest lesions, while ‘English Roseum’ had the largest. Lesions developed on all the wounded and unwounded inoculation sites on the ‘English Roseum’ and lesion size increased with increasing nitrogen fertility. Nitrogen fertility had no effect on lesion size on the other two cultivars.


Proceedings of the Sudden Oak Death Fourth Science Symposium 2010
Susan J. Frankel, John T. Kliejunas, and Katharine M. Palmieri, tech. coords.

Gen. Tech. Rep. PSW-GTR-229. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. 378 p

Abstract pdf Poster pdf


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

First Detector Workshops

First Detector Workshops

WSU Sudden Oak Death Education
Phytophthora ramorum Educate To Detect Program

Adapted from USDA National PRED Program for WSU Extension

Objective: To provide training on how to recognize symptoms potentially caused by Phytophthora ramorum and how to screen samples to determine if they should be submitted to the WSU Puyallup Plant and Insect Diagnostic Laboratory for P. ramorum testing.

Background: Sudden Oak Death (SOD) and Ramorum Blight are plant diseases caused by the fungal-like organism P. ramorum. This USDA-APHIS regulated pathogen was first identified in 2000 after killing thousands of tan oaks in California and causing a leaf blight on rhododendrons in Europe. Since then it has been found to infect many plants common to Washington’s natural and ornamental landscapes, including rhododendron, viburnum, big leaf maple, madrone, grand fir, and Douglas-fir. P. ramorum has spread to the natural landscape in 14 coastal counties in California, and one county in southwestern Oregon. Since 2003 this pathogen has been detected in western Washington nurseries and was first detected in a stream in 2006. The Washington State Department of Agriculture, in cooperation with the United States Department of Agriculture, is monitoring Washington’s nurseries and implementing eradication efforts to keep this pathogen from spreading to the natural environment or landscapes. This program has been designed to train Master Gardeners and WSU Extension affiliates as first detectors of P. ramorum, in the event that this organism is introduced into Washington’s landscape. Information provided will also be applicable to diagnosis and detection of other plant pathogens.

Program outline

1) Background and history of P. ramorum

2) Current status of P. ramorum in Washington

3) Introduction to WSU Sudden Oak Death Education program

4) Recognizing potential symptoms and determining if samples should be submitted for P. ramorum testing

Funding for this outreach has been provided by the USDA Forest Service, Pacific Southwest Region, Forest Health Protection

For information, please contact:

Marianne Elliott
Puyallup Research and Extension Center
2606 W. Pioneer
Puyallup, WA 98371-4998

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

Nursery research

Nursery research

Effect of Surface Sterilization Treatments on the Detection and Viability of Phytophthora ramorum on Various SubstratesIMG_0007 sm

Katie Coats, Kathy Riley, Gary Chastagner and Marianne Elliott, Washington State University, Puyallup Research and Extension Center, 2606 W. Pioneer, Puyallup, WA 98371;

An accurate evaluation of asymptomatic colonization of plant tissue by Phytophthora ramorum requires the ability to distinguish between the surface contamination or epiphytic growth of the pathogen and the colonization of plant tissues. Growth on selective media, such as CARP, following the surface sterilization of plant tissue is often used to confirm P. ramorum colonization of the tissue. The use of PCR to detect asymptomatic colonization of tissues requires that treatments kill pathogen propagules as well as render residual pathogen DNA on the surface of substrates undetectable. A series of surface sterilization tests were performed with two commonly used laboratory surface sterilants to determine their efficacy in killing epiphytic propagules of P. ramorum and rendering pathogen DNA undetectable in several different P. ramorum experimental scenarios. Substrates tested include detached rhododendron leaves, rhododendron leaf discs, and freshly harvested Douglas-fir wood. Whatman filter paper was included to represent an inert surface.

Results from preliminary tests indicate that the efficacy of a treatment varies by experimental scenario and detection method. Based on post-sterilization growth on CARP media, a 30-second treatment in a 10% solution of household bleach (0.6% sodium hypochlorite) one hour after a spore suspension of P. ramorum was applied to rhododendron leaves and leaf discs was as effective as higher concentrations of bleach and longer treatments in bleach in killing the pathogen on the surface of this host.  When spore suspensions were placed on Douglas-fir wood samples, a 30-second treatment in a 10% solution of bleach was not as effective as a 30-second treatment with 95% ethanol, based on CARP isolation data post-treatment. When spore suspensions were placed on Whatman filter paper and incubated for 2 days, a 10% bleach solution, 95% ethanol, and water each appeared equally as effective in preventing the detection of P. ramorum by isolation on CARP media post-treatment. When post-treatment quantitative PCR was used to detect the pathogen on Whatman filter paper and Douglas-fir, 10% bleach effectively removed DNA evidence of the pathogen while 95% ethanol and water were ineffective, leaving behind DNA at quantities comparable to those on non-treated substrates.

Additional studies are in progress and will be presented at the symposium.


Proceedings of the Sudden Oak Death Fourth Science Symposium 2010
Susan J. Frankel, John T. Kliejunas, and Katharine M. Palmieri, tech. coords.

Gen. Tech. Rep. PSW-GTR-229. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. 378 p

Abstract pdf Poster pdf


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