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Sudden Oak Death 2010 pilot study results and planning for 2011 monitoring

Notes from 7/29/10 Stream Monitoring For Phytophthora Meeting

About 15 people attended the meeting at the WSU Puyallup Research and Extension Center to get information on the work that was done in 2010 and to discuss improvements that could be made and possibilities for projects in 2011.

Marianne Elliott gave a Power Point presentation of an overview of Phytophthora diseases worldwide and of the sudden oak death (SOD) program at WSU-Puyallup.  She has set up a Facebook group called “Washington Sudden Oak Death” and also a blog (Washington SOD) where news items relevant to SOD in Washington are posted.

Katie Coats, our molecular diagnostician at Puyallup, gave a presentation on the 2010 experimental processes for leaf baiting of the stream sites, isolation from leaf material and the resulting Phytophthora and other fungi findings.  No Phytophthora ramorum, the cause of SOD, was detected from any of the stream baits.  There is a plan to expand the study to 10 sites in 2011.

The most common Phytophthora found in test streams was Phytophthora gonapodyides (“go-na-po-die-dees”), which was present at every location and historically not considered to be an important pathogen.  One of the findings from this year’s test was the discovery of a new “type” of  this phytophthora species,  which we nicknamed P. gonapodyides “A”, that has some unique characteristics that separate it from standard P. gonapodyides isolates, one of which was the presence of chlamydospores in culture.  A small pathogenicity test was conducted on rhododendron leaves, which yielded some very small lesions.  However, Dr. Chastagner noted that P. gonapodyides has been isolated from cankers on noble fir here at Puyallup and in other areas of the Pacific Northwest since the 1980’s, and its true importance as a pathogen is currently being debated.  Can it be pathogenic on economically important hosts, therefore making it more important to understand?

Dale Blum, a professor of microbiology from Pierce College in Puyallup, commented on the value of the educational and research experience for her 1st year biology students in a real life situation. The results of her students’ lab projects were presented.  Groups of students did a test of the effectiveness of the disinfectants commonly used to sterilize shoes as workers leave labs or outdoor areas where SOD is being studied. The assumption has been that these materials (10% bleach, Lysol, Formula 409, Simple Green) were able to kill any lingering Phytophthora spores.  These materials were tested on spore-inoculated soft and hard rubber sole-like materials, plus soft rubber coated in P. ramorum-infested soil.  None of the materials was able to kill all of the spores on the pieces with infested soil.  This reiterated the importance of cleaning soil and/or organic matter off of surfaces as much as possible before applying disinfectants.  There was a proposal made concerning the addition of surfactants to these solutions that might increase the effectiveness of the products.  They would like to possibly repeat this year’s experiment and add this factor to the new experiments.

Lucy Rollins, a newly-graduated Environmental Science major from the University of Washington-Tacoma, gave a presentation on their two Phytophthora projects.  The first was a combined stream monitoring study for the presence both E. coli and and P. ramorum in two urban streams in Tacoma, First Creek (in east Tacoma) and Puget Creek (in north Tacoma). First Creek is a well-exposed waterway in a heavily populated neighborhood as opposed to Puget Creek, which is a “protected urban stream”, complete with restoration projects of trees and shrubs, paths and buffer zones.  (Both streams have sewer lines that parallel them, which made them of interest for the E.coli portion of the work).  The study used leaves from two species of rhododendron, Rhododendron x ‘Nova Zembla’ and our native species, Rhododendron macrophyllum.  Three species of Phytophthora were identified from the leaf baits; P. gonapodyides, P. pseudosyringae and P. syringae, as well as 2 species of Pythium.

Their second project looked at the effect of salt water on the mycelial growth rate of the three genotypes of P. ramorum.  Colonies were able to grow even after exposure to the equivalent of a 100% sea water solution. The NA2 genotype was particularly unaffected by the salt water.  This is the genotype, along with EU1, that has been increasingly found in Washington nurseries and streams while the NA1 has been declining.  There was speculation that any buildup of salinity in potting media at nursery sites might favor the survival of the NA2 genotype.  There is interest in following up this mycelial test with one that studies the effect of salinity on the viability of the different spore types of the three genotypes of P. ramorum.

Dan Omdal from the WA Department of Natural Resources gave a quick review of his P. ramorum stream baiting work for 2010.  Three watercourses that had positives in 2009 were the primary focus this year; Harvey Creek, which drains into the Stillaquammish River near a former nursery site (no P. ramorum was found in 2010), Green River (no P. ramorum was found in 2010) and the Sammamish River which had positive P. ramorum finds in 2010.  Dan discussed the “quirks” of the finds, e.g. water in an ephemeral stream or ditch site would be positive, whereas year-round streams nearby might be negative.  He described how vegetation surveys to detect P. ramorum were done in areas where there were positive water baitings.  After 3-4 years of some stream locations being positive, and their subsequent vegetation surveys, there have been no positives from any of the vegetation surveys.  He has also tested muck/silt from positive streams and never had a positive.

The question was asked if some of the positive sites stay that way year after year because of possible infection on aquatic plants that maintains a “reservoir” of infected material.  Katie Coats also noted that, for some reason, there is now a greater genetic diversity in the more recent isolates.

There were questions about the water rights of the businesses located next to infected streams and the possibility of landscape infections if they used untreated water for irrigation purposes. What is the potential for infection of susceptible plants in the landscape?

A discussion was started concerning the possible projects and improvements that could be made in 2011.

  1. Should other known hosts of P. ramorum be used for the “extra” stream baiting sample in each bag rather than a random selection by the testing team?
  2. Is there additional training that would be helpful, to get new groups going?  The presence of a WSU researcher at the first leaf deployment was said to be very helpful.
  3. Do we need different thermometers?  The swimming pool ones did not always work well.
  4. Could there be more involvement of the volunteers/Master Gardeners with leaf processing in the lab?  “Long term” volunteers could be helpful in making media, transferring cultures and other routine tasks.
  5. We would like to get suggestions from DNR, WSDA and others for the location of new sites in 2011, plus more in Thurston, Clark, and Skagit Counties and Bremerton and Shelton.
  6. Coordinate with the WSDA and DNR and match their needs with volunteers and also check with Evergreen State College and more high schools to determine any interest in participating.
  7. The need to keep searching for funding sources and applying for grants.  Volunteer groups may be eligible for certain types of grants and there is a need for them to be on the lookout for new opportunities AND PROVIDE THAT INFORMATION TO RESEARCHERS.  It is also of vital importance that groups and their members who have participated in the research projects provide letters of support of the value the experience when grant applications are made.

Other ideas for student projects:

  1. UW has the technology for DNA sequencing and it can be done more cheaply at their facility and with faster results, and could provide more students with an opportunity to learn these techniques.
  2. Basic science projects related to the new P. gonapodyides “A” find, e.g. pathogenicity tests, colony growth and morphology studies, etc.  (This could be a subject for a high school or college senior project).
  3. Stream leaf baiting v.s. bottle sampling.  Rather than using leaf baits in streams to identify the species present, some researchers expand on their findings by collecting a 1-liter stream water sample for baiting, filter it, identify any species present, and then quantify the amount of inoculum that is present in the water sample.  Some researchers from Clemson who use this technique will be here next spring to do some tests.
  4. Doing a stream water temperature sequence, i.e. what species are found at various temperatures?  When is the water at the optimum temperature for testing for P. ramorum?
  5. More studies on P. gonapodyides and its potential to cause disease, especially on conifer species.  This could include inoculation of field-grown and potted trees, culture growth studies.  Also, there could be more work on the amount of diversity in streams.
  6. How susceptible are common aquatic plants to Phytophthora species, and particularly P. ramorum?  This could involve identifying aquatic species for testing and lab inoculation studies that could be done by students.
  7. Improvement of subculturing techniques, such as selecting from hyphal tips from different colonies with the use of a microscope.  Some cultures had multiple species and/or possibly multiple isolations of P. gonapodyides, but it was hard to separate them since they could grow on the same selective medium.
  8. Determining the phenotypic variation within the EU1 genotype population, by developing lineage markers.  We have received some grant funding for this project which could provide some experience for a student.

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