Nursery Research Findings and Education Initiatives. Jennifer Parke Oregon State University

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1 Nursery Research Findings and Education Initiatives Jennifer Parke Oregon State University

2 Belowground phase Asymptomatic root infection (Shishkoff, Parke) Persistence in infested potting media (Linderman) Recovery from organic debris in nursery substrate (Dart and Chastagner) Inoculum production from infected roots (Shishkoff) or buried infected leaf disks (Tjosvold)

3 Nina Shishkoff, USDA- ARS Ft. Detrick, MD

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5 Nina Shishkoff, USDA- ARS Ft. Detrick, MD

6 Sporangia and chlamydospore production from leaf disk in flooded conditions (one week, 20 o C, dark) Greenhouse C data 65 C fitted Chlamydospores (mean per leaf disk) C 95% LCL C 95% UCL S data S fitted S 95%LCL S 95% UCL Sporangia (mean per leaf disk) Weeks Steve Tjosvold, UC Extension, Santa Cruz, CA

7 Host susceptibility/resistance Differences in susceptibility among cultivars of rhododendron (Heungens, Grunwald), camellia (Shishkoff), lilac (Shishkoff), and viburnum (Grunwald) Effects of rhododendron cv. on pathogen epidemiology (Grunwald) Testing of rhododendron species for resistance to P. ramorum (Chastagner) Testing of nursery materials for use as diseaseresistant border plantings (Shishkoff)

8 Host susceptibility to P. ramorum Cultivar Experiment 1 Lesion area (%) 10 Vburk VplicMar Vlentago VlantMoh VopSteri VopCompa VdentNBu Vdent VtrilWen VdentChi VburkMoh VdentAut VplicSho VdentBlu VplicSha Vdavidii Identified viburnum and lilac cultivars that are resistant to P. ramorum 0 60 Experiment Lesion area (%) 10 Vburk VplicMar Vlentago VlantMoh VopSteri VopCompa VdentNBu Vdent VtrilWen VdentChi VburkMoh VdentAut VplicSho VdentBlu VplicSha Vdavidii Nik Grünwald 0 Viburnum host USDA-ARS HCRL Corvallis, OR

9 Effect of cultivar Cultivar LA a (%) Sporangia/ lesion Sporangia/ cm 2 lesion IP10 b (days) IP50 c (days) AULEC d Experiment 1 Boursault 17 a 46 a 15 a 1.6 b 2.1 b a Lee 6 b 17 b 12 a 1.8 a 2.6 a b Experiment 2 Boursault 19 a 287 a 68 a 1.6 b 1.8 b a Lee 8 b 139 b 78 a 1.8 a 2.0 a b Experiment 3 Boursault 11 a 83 a 36 a 1.6 b 2.2 b a Lee 4 b 25 b 31 a 1.7 a 2.5 a b Nik Grünwald USDA-ARS HCRL Corvallis, OR

10 Susceptibility of Rhododendron spp. to P. ramorum Cooperative project with the Rhododendron Species Foundation with support from the WSDA Nursery Research Program. Testing 40 species that are native to Yunnan (China), commonly cultivated, and/or commonly used in hybridizing. Preliminary data indicates there is a wide range in susceptibility among the species being tested.

11 Fungicide effectiveness Several fungicides found effective for use on woody ornamentals (Linderman, Tjosvold, Chastagner) Documentation of widespread resistance to metalaxyl in EU (Werres, Heungens)

12 Fungicide efficacy Ongoing project that is supported by the IR-4 program. Screened 13 fungicides for their effectiveness in protecting rhododendron leaves from infection in Some fungicides reduced disease development on wounded as well as nonwounded leaves. On non-wounded leaves, the most effective fungicides were Stature, Maneb, Dithane, NOA , Gavel, Polyram, Captan, and Segway. Some fungicides reduced infection up to 12 weeks after application. Inoc. ck Segway 12 wks

13 Water ecology P. ramorum present in recirculating water in nurseries (Werres) Slow sand filtration and lavagrain filtration effective in eliminating P. ramorum (Werres) Detection of Pr in streams near infested nurseries Abundance of Pr in streams appears to be related to temp and rainfall (Tjosvold) Relationship of waterborne propagules to disease (Werres, Tjosvold)

14 Slow Sand Filtration Supernatant water Filter Cover Filter surface (sand) Underdrain system (lowest level) with drainage for effluent Ufer et al. Federal Biological Research Centre for Agriculture and Forestry Institute for Plant Protection in Horticulture, Braunschweig, Germany

15 Detection of Phytophthora Sand filtration Run off Retention basin Filtrated water Aug Oct 2003 May Aug 2004 Oct May Aug 2005 Oct May Aug Oct 2006 Sampling month Bait leaf pieces with Phytophthora detection (%, n=15 ) Ufer et al. Federal Biological Research Centre for Agriculture and Forestry Institute for Plant Protection in Horticulture, Braunschweig, Germany

16 Stream Infective Propagules Statistical model using rain (4 day prior) and temperature (65 day prior) Steve Tjosvold, UC Extension, Santa Cruz, CA

17 Predicted disease occurrence 7 days before detection (2 day period) max. cfu / l / pear LW 2 o -12 o C Predicted_ #diseased_leaves 95% CI lower 95% CI upper Steve Tjosvold, UC Extension, Santa Cruz, CA

18 Population biology Recognition of 3 clonal lineages in N. American nurseries (NA1, NA2, EU1) Comparisons on biology and epidemiology of clonal lineages is underway (Heungens, Grunwald) Genotyping of isolates from infested nurseries (Grunwald, Chastagner, and others)

19 Genotypes of P. ramorum in Washington state nurseries and streams Cooperative project with WSDA and Nik Grunwald that is supported by the WSDA Nursery Research Program. EU1, NA1 and NA2 detected among 2005, 2006, and 2007 isolates. NA1 most common. Multiple genotypes and lineages commonly found in single nurseries. NA1 and EU1 lineages found on same plant in No evidence of sexual recombination. Sammamish river isolate has rare fingerprint matching single isolate from wholesale landscape supplier located outside of the watershed. Additional isolates from nurseries and two positive streams in WA are currently being genotyped.

20 Biology and epidemiology Characterization of temp and moisture conditions required for infection and/or sporulation (Grunwald, Tooley, Tjosvold) Dispersal in water and air: mock nursery (Heungens) Histological studies of infection (Werres)

21 Sporulation and infection Characterize conditions for sporulation and infection foundation for development of integrated P. ramorum management strategies Nik Grünwald USDA-ARS HCRL Corvallis, OR Sporulation (sporangia cm -2 lesion) Sporulation Minnetonka Boursault Experiment 1 Experiment 2 Experiment

22 Management and detection Disinfestation of nursery substrates with chemicals (Yakabe) and biological agents (Widmer) Effect of N fertilization on disease (Chastagner) Development of rapid, chip-based detection method for field use (Werres) Systems approach for identifying sources of contamination in nurseries (Parke & Grunwald)

23 Influence of N fertility on the susceptibility of rhododendrons to P. ramorum 2008 cooperative project with WSU Horticulturist Rita Hummel that is supported by the WSU Emerging Research Issues grant program. Three cultivars ( Compact P.J.M., Cunningham s White and English Roseum ). Three nitrogen rates. Assess infection, lesion development and sporulation.

24 A Systems Approach for Identifying Sources of Phytophthora Contamination in Nurseries Jennifer Parke and Carrie Lewis, Oregon State University Nik Grunwald, USDA-ARS Horticultural Crops Research Laboratory 4 nurseries, each sampled 6x/year 4 plant hosts ( (Pieris,, Rhododendron, Kalmia, Viburnum) ) at all stages of production year 1 and 2 Broadened to all Phytophthora hosts in year 2 Also sampled potting media and components, substrate, containers for re-use, irrigation pond water Goal is to identify sources of contamination and change management practices to alleviate the problem

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26 Recovery of Phytophthora species from nurseries A B C D Propagation plant substrate Greenhouse plant substrate Can yard plant substrate Potting medium/comp Used containers Irrigation water

27 Phytophthora species identification 183 Phytophthora isolates Most common species: P. cinnamomi (45), P. syringae (21), P. cryptogea (21), P. citrophthora (18), P. citricola (16), P. gonapodyides (16), P. megasperma (1), P. hevea (1), unidentified Phytophthora spp. (44)

28 New Education Initiatives WSU-WSDA WSDA program OSU-ODA ODA program

29 SOD Education: WSU and WSDA Hands on Nursery Training Pilot Study WSDA required all 2007 positive nurseries to attend. Training in BMPs and symptom recognition. 85% of participants report changing mgt. practices. Course handbook available at: Plant storage evaluation Symptom recognition

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35 5 6 B. Sporangia land on wet leaf, stem, or bud surface, and release zoospores which encyst, germinate and penetrate plant tissues A. Sporangia* develop on infected leaf, detach, and are transported via wind or water splash. C. Zoospores towards roots and colonize r 1 Sporangia produced on infected plants or plant debris wind or water splash to uninfected plants. 2 Leaves from infected but asymptomatic plants are us material D. Chlamydospores persist in leafy debris from infected plants and germinate to form new sporangia or hyphae. * not drawn to scale 3 Pathogen spreads from infected plants, leafy debris media via motile spores (zoospores) in ponded or stan 4 Pathogen-infested potting media leads to infection of ro 5 Pathogen is applied to plants via irrigation from co sources (i.e. surface water, recirculated water ponds, e 6 Pathogen is introduced from external sources such as forests. Phytophthora ramorum nursery disease cycle

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