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Washington State University
WSU Puyallup Ornamental Plant Pathology

Bulbs and Cut Flower Research Program

Bulbs and Cut Flower Research Program

Welcome

Welcome to the WSU Puyallup ornamental bulb plant pathology research website. Here you will find information on about our Disease Management Program for ornamental flower bulb crops.

We are currently working with growers of many different varieties, including: daffodil, dahlia, iris, lily, peony, and tulip. Please contact-us for more information or if you’re interested in participating in our Disease Management Program.

Bulbs and cut flowers, tulip festival

Disease Management Program

Research and education on diseases of ornamental flower bulbs has been conducted at WSU Puyallup for over 80 years. As the flower bulb industry has changed with the increasing urbanization of bulb-growing regions and concern over the potential environmental impacts from pesticides, we continue to direct our research toward solutions that enable growers to minimize crop losses from plant diseases and reduce the need for pesticides.

Currently, this internationally-recognized research program focuses on the development of DNA-based assays to quantify inoculum levels of soil-borne pathogens and determine appropriate control methods. We are also evaluating reduced-risk fungicides and alternative approaches to control pre- and post- harvest diseases that affect the economic viability of the flower bulb industry.

Research Outcomes

Bulbs and cut flowers, tulip festival

  • Identification of an effective reduced-risk fungicide to control gray bulb rot.  Use of this material reduces the amount of fungicide currently used by up to 98 percent.
  • Determination that chlorine dioxide (a common, food-grade disinfectant) is as effective as formaldehyde (a more hazardous chemical) in preventing the spread of basal rot during hot water treatment of bulbs.  Gaseous forms of this material also have the potential to replace fungicide bulb dips for control of Penicillium blue mold.
  • Identification of a number of reduced-risk fungicides that provide excellent control of foliar diseases on tulips, iris, and lilies.  In some cases, the use of these materials results in a 60 percent reduction in the amount of fungicides used by growers.
  • Demonstration that peak transmission of tulip break virus by aphids occurs during late April and early May.
  • Determination that the prevalence of viruses on lilies in Washington is moderate (36.3%) and the prevalence of viruses on dahlias in Washington is high (80.9%).

Education

Growers from Washington, Oregon, California, and British Columbia are provided the latest research information at annual Field Days and a Pacific Northwest (PNW) Flower Bulb Conference organized by WSU.

Gary leading educational activity

Partners and Support

  • Northwest Agricultural Research Foundation (NARF)
  • Wally Staatz Endowment
  • USDA Floral and Nursery Crop Research Initiative
  • WSDA Specialty Crop Block Grant
  • IR-4 program
  • Fred C. Gloeckner and Company, Inc.
  • Regional bulb and flower growers
  • Suppliers of professional products

Industry Background

Commercial flower bulb production in the PNW began over 100 years ago, and in the 1920’s, growers also supplied bulbs to greenhouse forcers in other regions of the U.S., Canada and Europe. Today, the production of both ornamental bulbs and cut flowers represents an important high-value specialty crop in the United States with 90% of the domestic production of tulips, daffodils, bulbous iris and Asiatic/oriental lilies occurring in the coastal areas of Washington, Oregon and northwestern California. In 2005, the wholesale value of flower bulb crops in the U.S. totaled over $235 million.

Currently, the majority of Washington’s specialty cut flower production occurs primarily on small farms in four counties: Clark, Lewis, Pierce, and Skagit. A WSU 2012 survey of Washington cut flower growers indicated that 98% of the growers farmed less than 10 acres and 51% of the growers farmed less than an acre.

Another WSU survey estimated there were 160 farmers markets in Washington in 2009 and 93% of these markets offered cut flowers for sale. Flowers from ornamental bulb crops are currently an important staple item at these local markets.

Cut flowers, photo credit: Edee Kulper

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; klriley@wsu.edu

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.

in

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
253-445-4596
melliott2@wsu.edu

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; kpcoats@wsu.edu

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.

in

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

Biology of P. ramorum


Biology of P. ramorum

Phenotypic variation in Phytophthora ramorum: wild type vs non-wild type isolates wt and nwt

M. Elliott, Washington State University, Puyallup Research and Extension Center, Puyallup, WA, USA 98371; melliott2@wsu.edu ; G. Sumampong, S. F. Shamoun, E. Becker, Canadian Forest Service, Pacific Forestry Centre, Victoria, BC, Canada V8Z 1M5; A. Varga, D. James, S. Masri, Sidney Laboratory, Canadian Food Inspection Agency, Sidney, BC, Canada V8L 1H3; and N. J. Grünwald, Horticultural Crops Research Laboratory, USDA ARS, Corvallis, OR, USA 97330

In earlier studies unusual culture morphology and behavior were noticed among some NA1 isolates of Phytophthora ramorum. This “non-wild type” behavior was not observed in our collection of isolates from the EU1 or NA2 lineages, even though the isolates had been in culture for a similar amount of time. It has been suggested that subculturing in vitro cause culture instability and loss of virulence, and passage through the host can revive the isolate back to its original state.  To study this, we compared four less virulent isolates (non-wild type; nwt) with four isolates of normal virulence (wild type; wt) in our culture collection.  One objective of this study was to determine whether wt behavior could be restored to nwt isolates of P. ramorum by successive re-isolation from host material. Detached leaves of rhododendron “Cunningham’s White” were inoculated with each of the isolates, which were re-isolated and tested for pathogenic aggressiveness, growth rate at maximum, optimum, and minimum temperatures, and chlamydospore production in vitro.

In both wt and nwt groups, there were significant differences in lesion size on detached rhododendron leaves between the original culture and the first re-isolation. Successive re-isolations were not different from the original culture and the first re-isolation. After re-isolation from the host, nwt isolates were still less aggressive than wt isolates. Along with lower aggressiveness on rhododendron leaves, nwt isolates produced fewer chlamydospores in V8 agar than did wt isolates.  There was no difference in growth rate between the original culture and the first re-isolation for most isolates.  However, nwt isolates were found to be more sensitive to temperatures below 2°C and above 28°C. The optimum growth temperature was 20°C.

Our preliminary results show that non-wild type isolates were more variable than wild type isolates in all of the characters tested, and were generally lower in aggressiveness, chlamydospore production, and growth rate at all temperatures for both the original culture and when re-isolated from a host. The greater variability suggests that these isolates are unstable or that slightly deleterious mutation(s) have accumulated in accordance with Muller’s ratchet resulting in reduced fitness. Wild type isolates performed better than non-wild type isolates in all of the phenotypic characters examined. Why nwt survives and proliferates is still a mystery. To understand the cause of these phenotypic differences, the role of cytoplasmic elements and differences in mitochondrial and nuclear DNA are being examined.

in

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