Source: WASHINGTON STATE UNIVERSITY submitted to
IDENTIFICATION OF PHYTOPHTHORA RESISTANT TRUE FIRS
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
REVISED
Funding Source
Reporting Frequency
Annual
Accession No.
0189047
Grant No.
(N/A)
Project No.
WNP00388
Proposal No.
(N/A)
Multistate No.
(N/A)
Program Code
(N/A)
Project Start Date
Aug 1, 2012
Project End Date
Jul 31, 2017
Grant Year
(N/A)
Project Director
Chastagner, G. A.
Recipient Organization
WASHINGTON STATE UNIVERSITY
240 FRENCH ADMINISTRATION BLDG
PULLMAN,WA 99164-0001
Performing Department
Puyallup Res & Ext Center
Non Technical Summary
American consumers purchase 28-32 million Christmas trees annually with a retail value of $976 million in 2010. Nationally, about15,000 farms grow Christmas trees on a total of 343,000 acres and employ over100,000 full or part-time workers. In 2006, five states (OR, NC, MI, PA, WA) accounted for 88% of the Christmas trees produced, and growers in the Pacific Northwest (PNW) produced 44% of the U.S. production. Although demand for noble, Fraser, and other true fir Christmas trees is increasing, Phytophthora spp. present a number of disease problems for growers. These include potential quarantines on the movement of trees due to the newly described exotic pathogen, Phytophthora ramorum, which is the cause of sudden oak death and ramorum blight and the difficulty of managing losses due to Phytophthora root rot (PRR). PRR, caused by several species of Phytophthora, is one of the most important diseases of true firs (Abies spp.) in Christmas tree plantations, nurseries, and landscapes. This disease has been associated with significant losses in noble and Fraser fir Christmas tree plantations wherever these species are grown and limits the ability of growers to expand the planting of these and other highly desirable species of Christmas trees. A survey of noble fir Christmas tree plantations in the PNW found that PRR occurred in almost 40% of the plantations sampled and caused up to 30% mortality. In other areas, such as North Carolina, annual losses due to root rot are estimated at $6-7 million. Phytophthora spp. Are fungus-like oomycetes, also known as watermolds, and disease development is favored by saturated soils. More than eight species of Phytophthora have been reported to cause root rot on true firs. Efforts to control this disease in Christmas tree plantations through cultural practices and the use of fungicides have generally been unsuccessful. Christmas tree growers in several major production regions have indicated that improved methods of managing PRR, including the identification of PRR-resistant true firs, is a high research priority. Development of PRR-resistant true firs is limited by the lack of information relating to pathogen variation and the interaction of various firs with the species of Phytophthora causing root rot in different production regions. Some species, such as P. cinnamomi are favored by warm soil temperatures and tend to occur in areas such as the Southern Appalachian Mountains, where rainfall occurs in conjunction with high soil temperature during the summer. In other production regions, such as the Pacific Northwest, high soil moisture levels occur during the fall through early spring when soil temperatures are much cooler. In these areas, a more diverse complex of species, including P. cambivora, P. cactorum, P. cryptogea, and P. citricola have been found to be associated with disease development. Thus, a clearer understanding of host x pathogen interactions is necessary to make knowledgeable recommendations to growers, and as a basic step toward developing resistant planting stock for the Christmas tree and nursery industries.
Animal Health Component
50%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
2120670116050%
2122110116025%
2122120116025%
Goals / Objectives
Phytophthora root rot (PRR), caused by several species of Phytophthora, is one of the most important diseases of true firs (Abies spp.) in Christmas tree plantations, nurseries, and landscapes. This disease has been associated with significant losses in noble and Fraser fir Christmas tree plantations wherever these species are grown and limits the ability of growers to expand the planting of these and other highly desirable species of Christmas trees. Recent studies have shown that there are some true firs that are resistant to some species of Phytophthora. To obtain a better understanding of the mechanism of resistance to PRR, we will: Identify the species of Phytophthora associated with PRR in different production regions in the U.S., investigate interactions between fir species and important species of Phytophthora important across U.S. Christmas tree production regions, and conduct histological studies of the infection and colonization process for representative susceptible and resistant firs to select species of Phytophthora. Understanding the mechanism of resistance to PRR has the potential to increase the use of Phytophthora-resistant true firs, which will reduce losses associated with the production of true fir nursery stock and Christmas trees, improve the economic viability of the industry, reduce the use of pesticides, and allow growers to meet the increasing demand for high quality Christmas trees. In addition, the results of this project will benefit growers beyond Washington and the PNW. It will also benefit a recently funded NCSU/WSU SCRI genomics project to identify molecular markers to assist the selection of Phytophthora-resistant true firs. This project will also result in the training of a Ph.D. student in Plant Pathology. Results of research will be disseminated through technical publications (i.e., refereed journal articles) and presentations at professional and industry conferences and field days, through popular publications, extension circulars, webinars, and subject-specific web pages.
Project Methods
To identify Phytophthora spp. associated with Phytophthora root rot (PRR) in different production regions, we will collect 10 root rot samples or isolates from a minimum of five sites in California, Connecticut, Pennsylvania, Michigan, North Carolina, Oregon, Washington, and Wisconsin. The 400 samples will be sent to WSU Puyallup where isolations will be done onto selective media to obtain a diverse collection of isolates of Phytophthora spp.. Morphological and molecular approaches will be used to identify specific Phytophthora spp.. Morphological assessments will include the characterization of sporangia, hyphal swellings, chlamydospores, production of oospores, mycelial growth rates, and growth at 5 and 35C. Molecular-based identification will be done using the ITS region of ribosomal DNA. Amplification of the ITS region will be performed and the PCR product will then be sequenced and compared to the Genbank database of DNA sequences utilizing a MegaBlast search technique. The DNA sequences will also be compared to several curated databases of known Phytophthora spp. A phylogenetic analysis will be done to determine the genetic variability among isolates of each species. Greenhouse inoculation trials will be conducted to determine variation in pathogen virulence and host susceptibility to the four most common regional Phytophthora spp. Three isolates will be selected for each species. These isolates will be used to inoculate one-year-old plug seedlings of the following eight (8) Abies species: balsam, Canaan, white, Fraser, momi, noble, Nordmann, Trojan, and Turkish fir. Seedlings will be grown during the first year and initial inoculation tests will be conducted during the second year of the project. Additional seedlings will be grown during the second year so that the inoculation trials can be repeated during the third year. Given that optimal temperatures for disease development vary for the different species of Phytophthora, inoculation tests will be conducted at two temperatures (17/20C and27/30C) each year. Using the results from the greenhouse inoculation tests, detailed histological studies will be conducted to obtain an understanding of how host x pathogen interactions vary by Phytophthora spp. The most virulent Phytophthora spp. will be used to conduct controlled inoculations of susceptible and resistant Abies roots and stems under the two temperature regimes used in the greenhouse pathogenicity trials. Using light and transmission electron microscopy and qPCR methods, we will determine differences in host x pathogen interactions and identify potential mechanisms of resistance. These studies will include examination of the attachment of zoospores, germ tube growth and appressorium formation, penetration of hyphae, and tissue colonization. In addition, sporulation of the Phytophthora spp. on susceptible and resistant host roots will be examined. Host structural changes will also be monitored to determine if there are specific types of host defense mechanisms associated with resistance.

Progress 01/01/13 to 09/30/13

Outputs
Target Audience: Plant Pathologists, Forest Managers, Christmas Tree Growers, Nurserymen, Regulators Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Participated in the IUFRO Shoot and Foliage Disease Conference. Brno, Czech Republic. May 20-25, 2013 and the IUFRO International Christmas Tree Research Conference. Truro, Nova Scotia, August 10-15, 2013. How have the results been disseminated to communities of interest? Results were reported to growers at an Integrated Pest Management for Christmas Trees in Aurora, OR, the PNWCTA Summer meeting and farm tour in Portland, OR and La Center, WA. and via two articles in the PNWCTA Lookout magazine and a USDA Forest Service Insect and Disease Leaflet. Results were shared with other scientists at the two IUFRO Conferences listed above. What do you plan to do during the next reporting period to accomplish the goals? During the coming year, the identification of species of Phytophthoras from different regions will be completed. Greenhouse and field trials will be initiated to investigate interactions between fir species and the most common species of Phytophthora. Histological studies of the infection and colonization process of selected species of Phytophthora on representative susceptible and resistant firs will also be initiated.

Impacts
What was accomplished under these goals? The focus of the research on this project this year has been the collection and identification of the species of Phytophthora associated with Phytophthora root rot (PRR) on Christmas trees in different production regions in the U.S. Samples of Christmas trees with PRR were obtained from 10 states (CA, CT, ID, MI, NC, NY, OR, PA, WA and WI). During interactions with growers, information was provided to them on potential PRR-resistant species that they may want to consider growing in sites that are conducive to the development of PRR. Isolates of Phytophthora were obtained from symptomatic tissues and morphological techniques and sequencing of the ITS region are being used to identify isolates. To date, the preliminary data suggests that the Phytophthora spp that cause root rot vary by production region.

Publications

  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Hummel, R.L., M. Elliott, G. A Chastagner, R. Riley, K. Riley, and A. DeBauw. 2013. Influence of Nitrogen Fertility on the Susceptibility of Rhododendrons to Phytophthora ramorum. HortScience 48:601-607.
  • Type: Other Status: Published Year Published: 2013 Citation: Chastagner, G. 2013. Recent Christmas Tree Research Grants Aim to Solve Major Problems for Industry. Lookout 46(1): 25-26.
  • Type: Other Status: Published Year Published: 2013 Citation: Landgren, C. and G. Chastagner. 2013. An update on Turkish/Trojan fir collaborative trial. Lookout 46(1): 27-28.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Chastagner, Gary A., Katie Coats, and Marianne Elliott. 2013. An Overview of Phytophthora ramorum in Washington State. p. 14-15. In: Frankel, S.J.; Kliejunas, J.T.; Palmieri, K.M.; Alexander, J.M. tech. coords. 2013. Proceedings of the Sudden Oak Death Fifth Science Symposium. Gen. Tech. Rep. PSW-GTR-243. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. 169 p.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Elliott, Marianne, Gary Chastagner, Katie Coats, and Gil Dermott. 2013. Determining the Risk of Phytophthora ramorum Spread From Nurseries Via Waterways. p. 55-59. In: Frankel, S.J.; Kliejunas, J.T.; Palmieri, K.M.; Alexander, J.M. tech. coords. 2013. Proceedings of the Sudden Oak Death Fifth Science Symposium. Gen. Tech. Rep. PSW-GTR-243. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. 169 p.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Chastagner, Gary, Kathy Riley, and Marianne Elliott. 2013. Susceptibility of Larch, Hemlock, Sitka Spruce, and Douglas-fir to Phytophthora ramorum. p 77-79. In: Frankel, S.J.; Kliejunas, J.T.; Palmieri, K.M.; Alexander, J.M. tech. coords. 2013. Proceedings of the Sudden Oak Death Fifth Science Symposium. Gen. Tech. Rep. PSW-GTR-243. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. 169 p.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Elliott, Marianne, Gary Chastagner, Simon Shamoun, Grace Sumampong, Ellen Goheen, and Alan Kanaskie. 2013. Biological Control of Tanoak and Bay Laurel Resprouts Using the Fungus, Chondrostereum purpureum. p134-136. In: Frankel, S.J.; Kliejunas, J.T.; Palmieri, K.M.; Alexander, J.M. tech. coords. 2013. Proceedings of the Sudden Oak Death Fifth Science Symposium. Gen. Tech. Rep. PSW-GTR-243. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. 169 p.
  • Type: Books Status: Published Year Published: 2013 Citation: Tjosvold, Steve, David Chambers, Gary Chastagner, and Marianne Elliott. 2013. Effect of Fungicides and Biocontrol Agents on Inoculum Production and Persistence of Phytophthora ramorum on Nursery Hosts. p 136. In: Frankel, S.J.; Kliejunas, J.T.; Palmieri, K.M.; Alexander, J.M. tech. coords. 2013. Proceedings of the Sudden Oak Death Fifth Science Symposium. Gen. Tech. Rep. PSW-GTR-243. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. 169 p.
  • Type: Books Status: Published Year Published: 2013 Citation: Chastagner, G. 2013. Challenges associated with the spread of Phytophthora ramorum in water from nurseries. P.4-5. In: McManus, K. A., and K. W. Gottschalk. 2013. Proceedings, 23rd U.S. Department of Agriculture interagency research forum on invasive species 2012. Gen. Tech. Rep. NRS-P-114. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station. 126 p.
  • Type: Books Status: Published Year Published: 2013 Citation: Elliott, M., Chastagner, G.A., Coats, K.P., DeBauw, A., & Riley, K. 2013. Volunteer stream monitoring for invasive Phytophthora species in Western Washington. P. 8. In: McManus, K. A., and K. W. Gottschalk. 2013. Proceedings, 23rd U.S. Department of Agriculture interagency research forum on invasive species 2012. Gen. Tech. Rep. NRS-P-114. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station. 126 p.
  • Type: Books Status: Published Year Published: 2013 Citation: Chastagner, G. A., and K. Riley. 2012. Effectiveness of a Swiss needle cast disease management program in controlling disease development in U.S. Pacific Northwest Douglas-fir Christmas tree plantations. Phytopathology 102 (Suppl. 6): S6.8.
  • Type: Books Status: Published Year Published: 2013 Citation: Talg�, V., G. Chastagner, A. Dobson, A. Stensvand, and I. M. Thomsen. 2013. Use of shade netting strongly reduces current season needle necrosis (CSNN). IUFRO International Christmas Tree Research Conference. Truro, Nova Scotia, August 10-15, 2013.
  • Type: Books Status: Published Year Published: 2013 Citation: Chastagner, G., A. McReynolds, and K. Riley. 2013. Mid-rotation growth and postharvest needle retention characteristics of balsam fir grown in western Washington. IUFRO International Christmas Tree Research Conference. Truro, Nova Scotia, August 10-15, 2013.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Presentation - Emerging adelgid problem on Nordmann fir, Swiss needle cast, and Phytophthora root rot. Wilbur-Ellis University, Auburn, WA. January 22, 2013.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Presentation - WSU projects at NORS-DUC. NORS-DUC Steering Committee Meeting. San Rafael, CA, March 11, 2013.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Presentation - Tree keepability: Improving the postharvest quality & safety of cut trees. Inland Empire Christmas Tree Assn. Spring Meeting. Spokane, WA. April 6, 2013.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Presentation - Overview of new research projects: Nordmann, Turkish and Trojan firs; adelgid; needle necrosis; needle retention and Phytophthora root rot; and more. Inland Empire Christmas Tree Assn. Spring Meeting. Spokane, WA. April 6, 2013.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Presentation - Risk Phytophthora ramorum poses to North American larch. IUFRO Shoot and Foliage Disease Conference. Brno, Czech Republic. May 20-25, 2013.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Presentation - Identification on needle cast and canker diseases of Christmas trees. Integrated Pest Management for Christmas Trees. OSU North Willamette Research and Experiment Station. Aurora, OR. June 3, 2013.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Presentation - An emerging adelgid problem on Nordmann and Turkish firs and new needle retention and Phytophthora root rot research. PNWCTA Summer Meeting. Portland, OR. June 21, 2013.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Presentation - Diagnosis and management of needle diseases of Christmas trees. PNWCTA Summer Meeting. Portland, OR. June 21-22, 2013.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Presentation - Update on postharvest needle retention research. SCRI Christmas Tree Genomics Project meeting. St. Louis, MO. July 30, 2013.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Presentation - Observations on the inspection of Christmas trees in Hawaii. IUFRO International Christmas Tree Research Conference. Truro, Nova Scotia, August 10-15, 2013.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Presentation - An emerging adelgid pest on Nordmann fir Christmas trees in western Washington. IUFRO International Christmas Tree Research Conference. Truro, Nova Scotia, August 10-15, 2013.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Presentation - Nordmann and Turkish fir: Phytophthora root rot, CSNN, bud break, and postharvest needle retention evaluations. IUFRO International Christmas Tree Research Conference. Truro, Nova Scotia, August 10-15, 2013.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Presentation - Washington State Report. NCERA-224: IPM Strategies for Arthropod Pests and Diseases in Nurseries and Landscapes Annual Meeting. Santa Barbara, CA. October 14-15, 2013.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Presentation - Biology of waterborne pathogens and the spread of Phytophthora ramorum in Washington. Whatcom County 19th Annual Master Gardener Advanced Training Workshop. Bellingham, WA. October 24, 2013.


Progress 01/01/12 to 12/31/12

Outputs
OUTPUTS: A variety of evaluations on trees at six regional replicated genetic trial sites in WA and OR were made in 2012. Each of these sites contained approx. 25 trees from each of 15 to 20 sources of Nordmann and Turkish firs. Bud Break - A bud break was rated on approx.3700 fir trees. Marketability and Value of Trees - Based on grades, the retail value of each tree at three of the sites was determined. Needle loss - Between late October and early November, needle loss testing was conducted on approx. 2800 trees in the six trials. In order to determine which of these trees had the best needle retention, two-year-old branches were harvested and displayed at 20 degrees C for 10 days. Phytophthora susceptibility - Data were collected from two replicated 6-year-old plots. One plot that includes two sources of Nordmann fir from two regions of the Republic of Georgia; Tlugi and Borshomi, and single sources of Fraser and noble fir. The other plot contains Nordmann fir from three different elevation levels of the Tlugi and Borshomi seed sources. In Tlugi, the elevation ranged from low (1230m) to medium (1450m) to high (1600m). In Borshomi, it ranged from low (920m) to medium (1030m) to high (1240m). This plot also contains a single source of Fraser and noble fir. Sudden Oak Death - <i>Phytophthora ramorum</i>, the fungus-like pathogen which causes sudden oak death, is a threat to the Pacific Northwest (PNW) nursery, Christmas tree, and forest industries. An increase has been seen in the NA2 and EU1 lineages from nursery samples in WA in recent years, so a study of the relative fitness of <i>P. ramorum</i> isolates in the Washington State University (WSU) culture collection was undertaken. Eighty-five isolates were screened for sensitivity to the fungicide mefenoxam and for relative pathogenicity on detached rhododendron leaves. The recent determination that <i>P. ramorum</i> is causing bleeding stem cankers on Japanese larch in the United Kingdom and that inoculum from this host appears to have resulted in disease and canker development on other conifers, including western hemlock, Douglas-fir, grand fir, and Sitka spruce, potentially has profound implications for the timber industry and forests in the PNW. A series of experiments were conducted to obtain a clearer understanding of the susceptibility of these conifers to <i>P. ramorum</i>. Industry presentations - Reports on this project were made at the Annual Pacific Northwest Christmas Tree Grower Association annual conference in March and summer meeting in June. A tour of field trials at Puyallup was also organized for the Puget Sound Christmas Tree Association annual meeting in August. A presentation relating to this project was made at the International Union of Forest Research Organization Fir Conference, which was held in Turkey in September 2012. PARTICIPANTS: Individuals who worked on this project include:<br> Katie Coats, Kathy Riley, Annie DeBauw, Andrew McRenolds, Gil Dermot, Katie McKeever and Marianne Elliott; Department of Plant Pathology, Washington State University.<p> Collaborators included:<br> Chal Landgren, Oregon State University,<br> growers and nurseries who provided plant material used in these studies.<p> Funding to support this project was obtained from:<br> Washington State Dept. of Agriculture (WSDA) Specialty Crop Block Grant program,<br> National Institutes of Food and Agriculture (NIFA) Specialty Crop Research program,<br> WSDA Christmas Tree Research program,<br> USDA Forest Service, Pacific Southwest Research Station<br> and the Pacific Northwest Christmas Tree Association. TARGET AUDIENCES: Plant pathologists, forest managers, christmas tree growers, regulators PROJECT MODIFICATIONS: This project was revised during 2012

Impacts
Bud Break - Bud break varied by site and there were also significant differences in the overall bud break rating for the different sources of trees in these trials. In general, the Turkish fir tended to break bud earlier than the Nordmann fir. There was a highly significant correlation in the bud break ranking from site to site, indicating that sources that broke bud earlier at one site also broke bud early at all of the other sites. Marketability and Value of Trees - These data indicated that there are very large family differences at each of the sites. Spearman rank correlation analysis of the data indicates that there is a very high correlation of the family values from one site to the next. Thus, families with the highest values at one site also had the highest values at the other sites. Based on the average family values across all three sites, there was an 89 percent increase in value from the lowest preforming family compared to the best preforming family. At 1,200 trees per acre, this translates to a difference of $7,865 per acre. In addition, two of the top five families were Nordmann fir and three were Turkish fir. Needle loss - Needle loss ratings varied by species, source, and site. The site with the lowest needle loss rating and the highest percentage of trees with needle loss ratings <1 was the Kings Valley site. Regression analysis indicated that there was a highly significant correlation between hours of accumulated temperatures <40 degrees F and the overall needle loss ratings at the sites. Phytophthora susceptibility - The percentage of Tlugi, Borshomi, Fraser, and noble fir trees that have been killed by Phytophthora root rot in the first plot was 0.0, 3, 93, and 100 percent, respectively. None of the Nordmann fir has been killed in the second plot, but 33.3 percent and 55.5 percent of the Fraser and noble fir, respectively have been killed. Isolations indicated that the mortality in these plots is due to <i>P. megasperma</i>. Sudden Oak Death - Most isolates of <i>P. ramorum</i> were sensitive to mefenoxam with the exception of some EU1 isolates from one nursery and its trace-forwards. A strong relationship between phenotypic characteristics such as fungicide sensitivity and pathogenicity, and the originating nursery was seen. Results from the conifer inoculation trials indicate that all of the conifer species tested, except eastern hemlock, exhibited some level of susceptibility to <i>P. ramorum</i>. The highest recovery of <i>P. ramorum</i> and level of symptom severity occurred on the larch species, especially western larch. These experiments also indicate that the NA1, and especially the NA2, genotypes of <i>P. ramorum</i> have as much potential as the EU1 genotype to cause disease on newly emerging growth of larch. Virtually no infection occurred on any of the larch inoculated in the fall. Additional studies are needed to determine the potential sporulation

Publications

  • Elliott M., G.A.Chastagner, G.M.Dermott, A.Kanaskie, R.Sniezko, J.Hamlin 2012. Range-wide genetic variability in Pacific madrone (Arbutus menziesii): examining disease resistance, growth, and survival in a common garden study. Proceedings of the fourth international workshop on the genetics of host-parasite interactions in forest trees. Ed. Sniezko, Richard A.; Yanchuk, Alvin D.; Kliejunas, John T.; Palmieri, Katharine M.; Alexander, Janice M.; Frankel, Susan J. USDA Forest Service, PSWRS. Pages 295-300.
  • Elliott M., G.A.Chastagner, A.DeBauw, G.M.Dermott, A.Kanaskie, R.Sniezko 2012. A first look at genetic variation in resistance to the root pathogen Phytophthora cinnamomi using a range-wide collection of Pacific madrone (Arbutus menziesii).. Proceedings of the fourth international workshop on the genetics of host-parasite interactions in forest trees. Ed. Sniezko, Richard A.; Yanchuk, Alvin D.; Kliejunas, John T.; Palmieri, Katharine M.; Alexander, Janice M.; Frankel, Susan J. USDA Forest Service, PSWRS. Pages 290-294. Report #PSW-GTR-240.
  • Chastagner G.A., G.Dermont, C.Benedict, A.I.Bary 2012. Early-rotation nonchemical weed management in Abies nordmanniana Christmas trees. Proceedings of the 10th International Christmas Tree Research and Extension Conference. Ed. Landgren, C.. 10th International Christmas Tree Researchand Extension Conference. August, 2011. Eichgraben, Austria. IUFRO. Pages 123-127.
  • Talgo V., G.A.Chastagner 2012. Phytophthora on Abies spp. (true firs). JKI Data Sheets, Plant Diseases and Diagnosis.
  • Chastagner G.A., K.Riley, C.Landgren 2012. Variation in the Development of Current Season Needle Necrosis on Noble, Nordmann, and Turkish Fir Christmas Trees in the United States Pacific Northwest. Proceedings of the fourth international workshop on the genetics of host-parasite interactions in forest trees. Ed. Sniezko, Richard A.; Yanchuk, Alvin D.; Kliejunas, John T.; Palmieri, Katharine M.; Alexander, Janice M.; Frankel, Susan J. USDA Forest Service, PSWRS. Pages 278-280. Report #PSW-GTR-240
  • Chastagner G.A., K.Riley, C.Landgren 2012. Variation in the development of current-season needle necrosis on noble, Nordmann, and Turkish fir Christmas trees in the U.S. Pacific Northwest. Proceedings of the 10th International Christmas Tree Research and Extension Conference. Ed. Landgren, C. 10th International Christmas Tree Research and Extension Conference. August, 2011. Eichgraben, Austria. IUFRO. Pages 85-87.
  • Elliott M., S.Shamoun, G.A.Chastagner 2012. An overview of Sudden Oak Death (SOD) disease caused by Phytophthora ramorum: Research results and challenges for the Pacific Northwest of North America. Proceedings International Symposium on Oak Forest Preservation. International Symposium on Oak Forest Preservation. August 2012. Korean Forest Research Institute. Seoul, Korea. Korean Forest Research Institute. Pages 30-45.
  • Chastagner G.A., G.Dermont 2012. Early-rotation growth characteristics of balsam fir grown in western Washington. Proceedings of the 10th International Christmas Tree Research and Extension Conference. Ed. Landgren, C. 10th International Christmas Tree Research and Extension Conference. August, 2011. Eichgraben, Austria. . IUFRO. Pages 1-4.
  • Chastagner G.A., G.Dermont, K.Riley, C.Landgren 2012. Nordmann and Turkish fir production in the U.S. Pacific Northwest: Preliminary budbreak and post-harvest needle retention evaluations. Proceedings of the 10th International Christmas Tree Research and Extension Conference. Ed. Landgren, C. 10th International Christmas Tree Research and Extension Conference. August, 2011. Eichgraben, Austria. IUFRO. Pages 4-11.
  • Hart J., G.A.Chastagner, G.Dermont, C.Landgren 2012. Rotational biomass and nutrient accumulation of four Christmas tree species. Proceedings of the 10th International Christmas Tree Research and Extension Conference. Ed. Landgren, C. 10th International Christmas Tree Research andExtension Conference. August 2011. Eichgraben, Austria. Pages 28-32.
  • Chastagner G.A. 2012. Spread of Phytophthora ramorum inoculum from nurseries to streams: Implications for the Christmas tree and specialty forest industries in the Pacific. Proceedings of the 10th International Christmas Tree Research and Extension Conference. 10th International Christmas Tree Research and Extension Conference. August, 2011. Eichgraben, Austria. IUFRO. Pages 84-85.


Progress 01/01/11 to 12/31/11

Outputs
OUTPUTS: In 2004, a series of replicated provenance/progeny trials were established in Washington and Oregon to identify sources of Nordmann and Turkish firs that are regionally adapted to Pacific Northwest climatic and production conditions and also exhibit superior postharvest needle retention characteristics. Preliminary bud break and needle retention evaluations were conducted on trees in some of these plantings. The results from these studies have been reported to Christmas tree growers in the Pacific Northwest at the annual PNWCTA conference and the Christmas tree scientific community at the Tenth IUFRO International Christmas Tree Research and Extension Conference in Austria. PARTICIPANTS: Individuals who worked on this project include Katie Coats, Kathy Riley, Annie DeBauw, and Gil Dermot; Department of Plant Pathology, Washington State University. Collaborators included growers and nurseries who provided plant material used in these studies. Funding to support this project was obtained from the USDA Forest Service, Pacific Southwest Research Station and the Pacific Northwest Christmas Tree Association. TARGET AUDIENCES: Plant Pathologists, Forest Managers, Christmas Tree Growers, Regulators PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Results of the bud break evaluations indicate that were was significant tree-to-tree variations in bud break, that bud break also varied by site and rating date. In general, the Turkish fir tended to break bud earlier than the Nordmann fir. A Spearman rank order correlation analysis indicated that there was a highly significant correlation in the bud break ranking for the different sources in these trials from site to site. This means that sources that broke bud earlier at one site also broke bud early at all of the other sites. Needle loss ratings varied by species, source, site, and harvest date. Delaying harvest increased needle retention. Overall, when branches were harvested on October 18th, only 19.5% of the trees had needle loss ratings < 1, which is the target value for acceptable needle loss. This increased to 61.6% when branches were harvested one month later. There was also a significant effect of site on needle loss ratings. Only 4.7% of the trees at a grower site had acceptable needle loss compared to over 60% at Puyallup when branches were harvested in mid-November. Additional information on the variation in bud break and postharvest needle retention will be collected from the trees in these plantings during the next two years. In May 2011, we installed environmental monitoring equipment at six of the Washington and Oregon planting sites on which we are focusing our evaluations. The environmental data will be used to obtain a better understanding of the effect of climatic conditions on the yearly variation in bud break and needle retention. We also plan on using these data to develop a degree-day model to predict the risk of needle retention problems.

Publications

  • Chastagner, G.A., M.Elliott, and K.M.McKeever. 2011. Sudden Oak Death. Agriculture Handbook 680, Forest Nursery Pests . USDA Forest Service. http://naldc.nal.usda.gov/download/CAT90930890/PDF
  • Chastagner, G.A., and K.Riley. 2011. First report of Phytophthora ramorum infecting mistletoe in California. Plant Health Progress. doi:10.1094/PHP-2011-0209-02-BR
  • Riley, K., G.A.Chastagner, and C.Blomquist. 2011. First Report of Phythophthora ramorum Infecting Grand fir in California. Plant Health Progress. doi:10.1094/PHP-2011-0401-01-BR


Progress 01/01/10 to 12/31/10

Outputs
OUTPUTS: A study characterizing Douglas-fir tissue colonization by the sudden oak death pathogen, Phytophthora ramorum, was completed during 2010. The results of this study have been disseminated via oral and poster presentations at the 2010 Western International Forest Disease Work Conference and were featured in an abstract in the California Oak Mortality Task Force 2010 December Newsletter. PARTICIPANTS: Individuals who worked on this project include Kathleen McKeever, M.S. Degree graduate student; Marianne Elliott, Katie Coats, Kathy Riley, Annie DeBauw, and Gil Dermot, Department of Plant Pathology, Washington State University. Collaborators included Willus Littke (Weyerhaeuser), and growers and nurseries who provided plant material used in these studies. Funding to support this project was obtained from the USDA Forest Service, Pacific Southwest Research Station and the Washington State University Puyallup Chicona Endowment Fund. TARGET AUDIENCES: Plant pathologists, forest managers, Christmas tree growers, regulators. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Artificial inoculation experiments were carried out to provide a thorough analysis of the colonization of Douglas-fir by P. ramorum. Goals of this research included determining which tissues are colonized by the pathogen, whether woody tissues are able to support sporulation, the likelihood of stem infections occurring on Douglas-fir with intact bark, and the viability of the pathogen in foliage. Methods employed included isolation, ELISA, and histological examination of stem tissues; qPCR and isolation to determine colonization efficacy and viability of the pathogen in needle tissues; and baiting studies to determine the ability of Douglas-fir bark to inhibit colonization of Rhododendron leaves by the pathogen. ELISA results showed that proteins of the pathogen were detectable in the phloem, cambium, and superficial xylem, with infrequent detection in asymptomatic tissues. The pathogen was able to be isolated from all symptomatic woody tissues tested, but not from non-discolored tissues. ELISA and isolation techniques produced results that were highly positively correlated (r2=0.62, p=0.78), and histological observations paralleled information derived from these techniques. Douglas-fir bark reduced infection on Rhododendron leaf baits by up to 83 percent in the presence of inoculum. Results from foliage inoculations indicated that pathogen DNA is detectable using qPCR methods, but there was an inability to isolate the pathogen from needle tissue. Evidence of spore formation in woody stem tissues has not been observed. It was concluded that the pathogen may be able to infect into the shallow xylem tissues of Douglas-fir in the presence of wounding, but there was no evidence of sporulation in tissues. The inability to isolate the pathogen from non-discolored tissues suggests that the proteins detected by ELISA outside of the lesion may be elicitins that are secreted in advance of hyphal colonization. The inability to isolate the pathogen from colonized needles may indicate the presence of chemical inhibitors that render the pathogen non-viable subsequent to initial infection. Finally, the ability of Douglas-fir bark to suppress infection of Rhododendron leaf baits suggests that the bark is inhibitory to P. ramorum and that infection of woody stem tissues through intact bark may be limited. Further research is required to identify the nature of this inhibition. Characterization of P. ramorum colonization of Douglas-fir tissues is relevant to our current understanding of the behavior of the pathogen in different hosts and may enhance our ability to assess risk and create adequate regulations to thwart the spread of this exotic pathogen.

Publications

  • Talgo, V., G.A.Chastagner, I.M.Thomsen, T.Cech, K.Riley, K.Lange, S.S.Klemsdal, and A.Stensvand. 2010. Sydowia polyspora associated with current season needle necrosis (CSNN) on true fir (Abies spp.).. Fungal Biology. 114:545-555.
  • Chastagner, G.A., and K.Riley. 2010. First report of Phytophthora ramorum infecting red fir in California. Plant Disease. 94:1170.


Progress 01/01/09 to 12/31/09

Outputs
OUTPUTS: Phytophthora root rot is a common disease in Christmas tree plantations. A replicated field trial was established in 2004 to determine the susceptibility of 79 sources of 14 Abies spp. to this disease. The trial consists of 100 3m X 3m cells laid out in a checkerboard design. A single seedling from each source was planted in each cell. To encourage disease development, individual cells were flooded for 2 to 3 days during the growing season in 2007, 2008, and 2009. Initial symptoms, wilting and branch flagging, were evident on some trees by early summer 2007. Since then, the incidence of symptomatic trees has increased each year. To obtain preliminary data on the susceptibility of each of the different species and sources of trees in this experiment, all of the trees in 26 of the cells were excavated during late June to early August 2009. Symptoms were recorded for each tree and the root systems were washed and examined for evidence of root rot. Isolations were done from symptomatic roots and stems to determine the Phytophthora species associated with root rot. Over 70% of the Shasta fir and 60% of the noble fir were killed by root rot. White fir (30%) and Fraser fir (23%) were the next most susceptible species. Less than 5% of the Turkish, Nordmann, grand, Nikko, and Canaan fir had evidence of root rot. Isolations indicated that the root rot in this trial was caused by P. cambivora, P. cryptogea, P. citricola, and P. gonapodyides. PARTICIPANTS: Pacific Northwest Christmas Tree Association TARGET AUDIENCES: Commercial Christmas tree growers, nurseries, retailers, and consumers PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
During the past 20 years, there has been a significant increase in the demand for true fir Christmas trees. Noble fir has excellent needle and moisture retention characteristics and now accounts for about 50% of the production in the Pacific Northwest (PNW). The expansion of noble fir plantings is limited by their susceptibility to several diseases, including Phytophthora root rot. Once this disease occurs in a plantation, there are currently no economically effective ways of controlling it. One potential means of reducing the impact of this disease is the identification of true firs (Abies spp.) resistant to this disease that could be grown in Phytophthora conducive sites. Our research has shown that Turkish, Nordmann, grand, Nikko, and Canaan fir have good field resistance to this disease. Of these species, there is considerable interest in growing Nordmann and Turkish fir because of their resistance to several other disease and insect pests in the PNW. One weakness of these species is their variable needle retention. To address this issue, we are screening 20 sources of Nordmann and Turkish fir for needle retention. Preliminary results from this research have identified a number of individual trees and a source of Nordmann fir from Denmark that have superior needle retention. If these results are confirmed with additional studies over the next few years, growers will be able to introduce this source of trees into the nursery trade and eventually provide consumers with high quality Nordmann fir from sites where noble fir can not be grown.

Publications

  • Hollingsworth, R.G., G.A.Chastagner, N.J.Reimer, D.E.Oishi, P.J.Landolt, and R.E.Paull. 2009. Use of shaking treatments and pre-harvest sprays of pyrethroid insecticides to reduce risk of yellowjackets and other insects on Christmas trees imported into Hawaii. Journal of Economic Entomology. 102(1):69-78.
  • Grunwald, N.L., E.M.Gross, K.L.Ivors, M.Garbelotto, F.N.Martin, S.Prospero, E.Hansen, J.M.Bonants, R.C.Hamelin, G.A.Chastagner, S.Werres, D.M.Rizzo, G.Abad, P.Beales, G.Bilodeau, C.Blomquist, C.Brasier, S.Briere, A.Chandelier, J.Davidson, S.Denman, M.Elliott, S.Frankel, E.Goheen, H.de Gruyter, K.Heungens, D.James, A.Kanaskie, M.McWilliams, W.Man in't Veld, E.Moralejo, N.Osterbauer, M.Palm, J.Parke, A.Sierra, S.Shamoun, N.Shishkoff, P.Tolley, A.Vettraino, J.Webber, and T.Widmer. 2009. Standardizing the Nomenclature for Clonal Lineages of the Sudden Oak Death Pathogen, Phytophthora ramorum. Phytopathology. 99(7):792-795.
  • Talgo, V., I.M.Thomsen, G.A.Chastagner, T.Cech, K.Lange, B.Perny, K.Riley, B.Louis, A.Dobsen, and A.Stensvand. 2009. Fungicidforsog mod CSNN pa nordmannsgran i Europa og USA. Naledrys 67:30-35.
  • Gross, E.M., M.Larsen, G.A.Chastagner, D.Givens, and N.L.Grunwald. 2009. Population genetic analysis infers migration pathways of Phytophthora ramorum in US nurseries. PLOS Pathogens 5(9):e1000583.


Progress 01/01/08 to 12/31/08

Outputs
OUTPUTS: In our continuing effort to understand the risk Phytophthora ramorum poses to the Christmas tree and forest product industries a large replicated field trial was established within a regulated area near Los Gatos, CA to determine the ability of this exotic pathogen to colonize the stems of Douglas-fir and grand fir Christmas trees. The stems on approximately 75 trees of each species were inoculated with mycelial plugs just beneath the bark during fall 2007 and late winter 2008. The progression of symptom development has been monitored periodically throughout the year and a subset of the trees has been harvested to allow for examination of the inoculated stems. Four months after inoculation, cankers were evident on a slightly higher percentage of the Douglas-fir trees that were inoculated in the winter (93.8%) compared to the fall (79.7%). Most of the fall and winter inoculated trees exhibited extensive resin flow in July and November. Branch flagging in the area of the cankers was evident on some trees. On the fall-inoculated trees, there was a slight increase in canker length between March and July. The average canker size on the winter-inoculated trees was about half the size of the cankers on the fall-inoculated trees. The longest canker on the fall-inoculated trees was 45.7 cm long and the longest canker on the winter-inoculated trees was 39.4 cm long. The size of cankers on the grand fir was much smaller than the size of those that developed on the Douglas-fir. Four months after inoculation, about twice as many of the trees inoculated in the winter (77.3%) had visible cankers compared to those inoculated in the fall (35.6%). Although some cracking of the bark was observed in the canker area, very little resin flow was observed. On the fall-inoculated trees, the average canker length was still only about 2.0 cm one year after inoculation. On the winter-inoculated trees, the average length of cankers in July was 4.7 cm. Eight months after inoculation (November), canker lengths had increased slightly to 6.1 cm. the largest canker on any of the inoculated trees was 25.1 cm long and 7.6 cm wide. No cankers were observed on any of a subset of trees of either species inoculated during the summer. Isolation and PCR testing is underway to determine what stem tissues are being colonized by the pathogen. Needle loss is a significant problem affecting the marketability of cut Christmas trees. While delaying harvest and proper tree care can help minimize potential needle loss problems, needle loss can still be a significant problem for some species of Christmas trees. During the past 10 years we have used a detached branch test to identify Balsam, Canaan, Douglas, Nordmann, and Turkish fir trees that have genetically superior needle retention characteristics. This research has been done with university and industry cooperators in Oregon, Ohio, Pennsylvania, Michigan, New Hampshire, Nova Scotia, and Denmark. To preserve genetically superior trees, scion wood is collected from trees that have been tested for a minimum of two years and grafted into clonal holding blocks at WSU Puyallup for future testing and distribution to industry partners. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Commercial Christmas tree growers, nurseries, retailers, and consumers PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Current regulations regarding the movement of known conifer host material out of regulated areas infested with Phytophthora ramorum are based on the apparent inability of this pathogen to colonize the woody tissues of stems under natural conditions. There is increasing concern among some trading partners about the ability of this pathogen to colonize conifer woody stem tissues. The stem inoculation studies we are doing will provide information on the potential risk that this pathogen may have on the ability to colonize conifer stem tissues. It will also shed light on factors affecting stem colonization and symptom development. The archiving of tested sources of Christmas trees with superior needle retention characteristics will provide access to material for future testing to better understand the underlying physiological basis that triggers needle shedding and provide industry partners with scion wood for establishment of future seed orchards.

Publications

  • Antonelli, A.D., D. Tapio, J. Stark, and G.Chastagner. 2008. Failure of registered products to control needle midge Lookout 41(3): 26-27.
  • Chastagner, G.A., E. Hinesley, and K. Riley. 2008. Effect of two fire retardants on postharvest drying and flammability of Douglas-fir and Fraser fir Christmas trees. HortScience: A Publication of the American Society for Horticultural Science. 43(1):203-205.
  • Chastagner, G.A. 2008. Potential effect of climate change on the postharvest quality of Christmas trees. Great Lakes Christmas Tree Journal. Winter (2008) Page 6.
  • Bates, R. and G.A. Chastagner. 2008. Joint research project aims to identify superior sources of Canaan fir. American Christmas Tree Journal. 52.5 Pages 12-13.
  • Chastagner, G.A. 2008. Risk of Phytophthora ramorum infection in Christmas trees. An update. American Christmas Tree Journal. 52.5 Pages 18-19.
  • Chastagner, G.A., A. DeBauw, and K. Riley. 2008. Rehydration of noble and Fraser fir Christmas trees: Effect of interval between re-cutting the base of a tree and its placement in water. Christmas Tree Lookout. 41.2 Pages 29-30.
  • Chastagner, G.A., K. Riley, and N.L. Dart. 2008. Phytophthora ramorum isolated from California bay laurel inflorescences and mistletoe: Possible implications relating to disease spread. http://.treesearch.fs.fed.us/pubs/29877
  • Frankel, S. J., J. T. Kliejunas, and K. M. Palmieri, Tech. Coords., 2007. Proceedings of Gen. Tech. Rep. PSW-GTR-214. Albany, CA: USDA Forest Service, Pac. SW Res. Stat. 491 p. The sudden oak death third international science symposium. March, 2007. Santa Rosa, CA. Pages 167-172. http://www.fs.fed.us/psw/publications/documents/psw_gtr214_000_fm_cvr _div.pdf
  • Chastagner, G.A., K. Riley, and N.L. Dart. 2008. Spread and development of Phytophthora ramorum in a California Christmas tree farm. Frankel, S. J., J. T. Kliejunas, and K. M. Palmieri, Tech. Coords., 2007. Proceedings of the sudden oak death third science symposium. Gen. Tech. Rep. PSW-GTR-214. Albany, CA: USDA Forest Service, Pac. SW Res. Stat. 491 p. The sudden oak death third international science symposium. March, 2007. Santa Rosa, CA. Pages 199-200. http://www.fs.fed.us/psw/publications/documents/psw_gtr214_000_fm_cvr _div.pdf
  • Chastagner, G.A., A. DeBauw, K. Riley, and N.L. Dart. 2008. Effectiveness of fungicides in protecting conifers and Rhododendrons from foliar infection by Phytophthora ramorum. Frankel, S. J., J. T. Kliejunas, and K. M. Palmieri, Tech. Coords., Proceedings of the sudden oak death third science symposium. Gen. Tech. Rep. PSW-GTR-214. Albany, CA: USDA Forest Service, Pac. SW Res. Stat. 491 p. The sudden oak death third international science symposium. March 2007. Santa Rosa, CA. Pages 325-334. http://www.fs.fed.us/psw/publications/documents/psw_gtr214_000_fm_cvr _div.pdf
  • Dart, N. L. and G. A. Chastagner. 2008. Estimating the economic impact associated with the destruction of plants owing to Phytophthora ramorum quarantine efforts in Washington State. Pp 341-344. In: Frankel, S. J., J. T. Kliejunas, and K. M. Palmieri, Tech. Coords., Proceedings of the sudden oak death third science symposium. Gen. Tech. Rep. PSW-GTR-214. Albany, CA: USDA Forest Service, Pac. SW Res. Stat. 491 p.
  • Frankel, S. J., J. T. Kliejunas, and K. M. Palmieri, Tech. Coords., Proceedings of the sudden oak death third science symposium. Gen. Tech. Rep. PSW-GTR-214. Albany, CA: USDA Forest Service, Pac. SW Res. Stat. 491 p. The sudden oak death third international science symposium. March, 2007. Santa Rosa, CA. Pages 341-344. http://www.fs.fed.us/psw/publications/documents/psw_gtr214_000_fm_cvr _div.pdf


Progress 01/01/07 to 12/31/07

Outputs
OUTPUTS: To assess the potential risk associated with the movement of P. ramorum via infected Christmas trees, the spread and development of P. ramorum has been monitored since 2005 in a 23-acre U-cut Christmas tree farm within a regulated area near Los Gatos, CA. A series of 6 transects were established in 2005 from the edge of the forest into the Christmas trees in this area to monitor the spread of P. ramorum. The level of infection and extent of shoot dieback was assessed on tagged Douglas-fir and grand fir trees along these transects periodically during the spring and summer. Environmental conditions during spring 2005 were much more favorable to initial shoot tip infections than in 2006 and 2007. In 2005, where grand fir were underneath the canopy of infected California bay laurel, virtually all of the new shoots were infected shortly after bud break. Infection appeared to be related to precipitation events during bud break. The progression of dieback on infected shoots of Douglas-fir and grand fir progressed for about 4 weeks after the initial appearance of symptoms, typically spreading about 5 cm into the previous year's growth. The extent of dieback did not increase between early summer and mid-November. Our data also indicate that distance from infected plants (predominantly California bay laurel) within the forest is an important factor relating to the infection of the Douglas-fir and grand fir Christmas trees. Most of the infected Christmas trees occurred within 2 to 4.4 meters of the edge of the forest. Virtually no infection was evident on Christmas trees that were 5 to 8 meters away from the forest edge. In an effort to identify sources of Nordmann and Turkish fir that perform well as Christmas trees, needle loss was assessed on trees in five replicated regional test plantings. These plantings ranged from Springfield, OR north to Satsop, WA. Each planting contained 25 trees from each of eight sources. These included progeny from 1) a tree in the Peavy Arboretum at OSU (TP), 2) a tree in the Kintigh seed orchard near Eugene (TK), and trees from the Bolu-Kokez provenance in Turkey (TB). In addition there were trees from the following five provenances of Nordmann fir: Ambrolauri (NA), Borshomi (NB), Savsat Yayla (NSY), Savsat-Meydancik (NSM), and Savsat-Velikoy (NSV). A single branch was harvested from the north and south side of each tree during early October and early December to assess differences in postharvest needle retention. Needle loss was highly variable, ranging from branches that did not lose any needles to ones that completely defoliated. Based on the percentage of trees that had < 5% needle loss, the following had a significant effect on needle loss severity: site, source, harvest date (Oct. > Dec.), and needle age (2005 > 2006). Branch location (north vs. south) had no effect on needle loss. The percentage of trees that did not shed any needles ranged from a high of 16 to 20% for the TB and TP sources of Turkish fir to a low of 5% for the NSM source of Nordmann fir. When harvested early, the TB source of Turkish fir had a significantly higher percentage of trees with superior needle retention at all sites. TARGET AUDIENCES: Commercial Christmas tree growers, nurseries producing conifer seedlings, retailers, consumers

Impacts
Our Phytophthora ramorum studies indicate that Christmas tree growers can minimize the risk of infection by this exotic pathogen by avoiding planting trees in close proximity to high inoculum producing hosts like California bay laurel or by removing such hosts along the perimeter of their plantings. Our needle retention studies indicate that growers could significantly improve the postharvest quality of Nordamann and Turkish fir by identifying locally adapted seed sources that exhibit superior needle retention.

Publications

  • Dart, N. L., and Chastagner, G. A. 2007. Estimated economic losses associated with the destruction of plants due to Phytophthora ramorum quarantine efforts in Washington State. Online. Plant Health Progress May doi:10.1094/PHP-2007-0816-01-BR.
  • Chastagner, G.A., and E.Hinesley. 2007. Effectiveness of I-V watering devices in maintaining postharvest freshness and quality of cut Christmas trees. Postharvest Biology and Technology. 43:178-181.
  • Dart, N.L., G.A.Chastagner, and T.Peever. 2007. Spread of Heterobasidion annosum in US Pacific Northwest Christmas tree plantations. Phytopathology. 97(5):511-556.
  • Dart, N.L., G.A.Chastagner, K.Riley, and E.Rugarber. 2007. Quantifying inoculum levels of Phytophthora ramorum and other Phytophthora species in the soil profile of ornamental retail nurseries. Plant Disease. 91:1419-1422.
  • Dart, N. L., and Chastagner, G. A. 2007. High recovery rate of Phytophthora from containerized nursery stock pots at a retail nursery highlights potential for spreading exotic oomycetes. Online. Plant Health Progress August doi:10.1094/PHP-2007-0508-02-RS.


Progress 01/01/06 to 12/31/06

Outputs
Limited information is available regarding the susceptibility of various Abies spp. to Phytophthora root rot under field conditions. A series of 100 "mini plantings" that contain trees from 41 of the families included in the 2004 OSU noble fir test, 19 of the sources included in the 2004 OSU/WSU Nordmann and Turkish fir progeny and provenance test, as well as balsam, Canaan, European silver, Fraser, grand, Korean, Momi, Nikko, Shasta, Veitch, and white fir were established in 2004. Six additional sources of Nordmann fir and one source of King Boris fir were added to each planting in 2006. During summer 2006, 20 mini plantings were inoculated with each of the following Phytophthora spp: P. cinnamomi, P. cactorum, P. cryptogea, and P. cambivora. The remaining 20 plantings were not inoculated and serve as checks. The Phytophthora species selected are those most often associated with tree mortality in PNW Christmas tree plantations. Following inoculation, the plantings were irrigated continuously for several days to create the saturated soil conditions that favor the development of Phytophthora root rot. Mortality data will be collected from this test through next summer to determine if there are differences in the susceptibility of these trees to Phytophthora root rot. Postharvest needle retention studies have shown that for most Abies spp. that are grown as Christmas trees, delaying harvest significantly reduced needle loss problems. Since trees are sometimes harvested early and held in storage piles for various periods of time before they reach the market, a study was conducted to determine if similar changes in needle retention also occurred while trees are in storage. We harvested branches from 20 Fraser fir and 21 Canaan fir trees on October 18, 2005. Three branches from each tree were immediately displayed in a room maintained at 68F and assessed for needle loss. The remaining branches were placed in vented plastic crates, and held outdoors under shade cloth. To determine if changes in needle loss patterns were similar for the branches in storage to freshly harvested branches from the trees, additional sets of three stored branches from each tree were removed from the crates and a set of three freshly harvested branches was tested for needle loss every two weeks through November 29, 2005. After 10 days of display, the extent of needle loss was rated on a scale of 0 to 7, where 0 = no loss and 7 = >75% of the needles lost. On the initial harvest date, the average needle loss rating for the Fraser and Canaan fir was 1.8 and 3.5, respectively. As expected, the severity of needle loss decreased on the branches that were harvested at later dates. For the branches that were harvested on November 29th, the average needle loss ratings had dropped to 0.5 and 0.7 for the Fraser and Canaan fir, respectively. The change in needle loss on the branches in storage was very similar to the changes seen with the freshly harvested branches. There was a comparable improvement in needle retention for both freshly harvested branches and branches that were in storage.

Impacts
There are a number of observational reports that indicate that some types of true firs are tolerant to Phytophthora root rot under field conditions. Since it is not possible to economically control this disease in the field, the identification of tolerant Abies spp. would be a significant step in reducing losses that are caused by this disease. Our needle retention studies have the potential to open up new areas of research that are likely to increase the ability of growers to improve the quality of trees shipped to consumers.

Publications

  • No publications reported this period


Progress 01/01/05 to 12/31/05

Outputs
Annosus root rot (Heterobasidion annosum) has become a major problem in many noble and Fraser fir Christmas tree plantations in the Pacific Northwest, killing up to 40% of the trees prior to harvest. Stump removal before replanting is commonly recommended as one approach to minimize development of this disease. To compare the effectiveness of five different approaches to removing stumps and roots, a field trial was conducted in a recently harvest noble fir plantation. All treatments decreased the dry weight of recovered material compared to the control plots. The total weight of residual material left after grinding was higher than either of the stump extraction treatments and all of the grinding plots tended to leave a greater amount of root pieces than the extraction plots. The mass of residual stumps left in the field following a Evergreen strip grinding treatments was clearly higher than the broadcast grinding treatment with this grinder or when a Fecon grinder was used. In part this resulted from stumps that were off center and were only partly partially ground by the grinder. In all of the grinder plots, only the tops of some of the stumps were ground off, leaving much of the stump and root system below the 8-inch grinding depth largely intact. The use of an excavator to remove stumps, especially one equipped with a brush rake resulted in the least amount of residual stump material. This treatment was clearly the most effective in minimizing the amount of larger, residual stump pieces that remained in the field, which is where Annosus is more likely to survive for extended periods of time. During the past three years, we have been studying the effect of harvest date on the needle retention of 10 true fir species. A single, fully exposed 2-year-old branch was harvested in the upper third of each tree during October, late November/early December and mid January during each year. These branches were displayed in a room maintained at 18 to 20C and needle loss was rated on a 0 to 7 scale. Needle loss was evident on some branches after just 3 days. By day 7, some branches had lost almost all of their needles. Over the 3 years of testing, the average needle loss ratings after 10 days for the branches harvested in October ranged from 0.2 to 5.7 on a 0 to 7 scale. Most species had significant needle loss problems when harvested in October, though some individual trees did not shed any needles. Noble and Korean fir were the least likely to shed needles when harvested in October. Delaying harvest reduced, but did not eliminate needle loss. With some species, such as Shasta, balsam, Fraser, and particularly Canaan fir, the reduction was very dramatic. However, even when branches were harvested in January, some of the Nordmann, Turkish, grand, and particularly white fir trees still had significant needle shedding problems. For some trees, no needle loss was ever observed, regardless of harvest date, over the 3 years of testing. Given the level of tree-to-tree variation seen in this experiment, it is likely that potential needle loss problems for many of these species could be significantly reduced through a genetic selection process.

Impacts
Our Annous stump removal research has provide growers with important information on the relative effectiveness of different types of equipment in removing stumps and roots in an effort to control this disease. For many growers, they will be able to improve their disease control by switching to the use of an excavator to remove stumps from their fields. Our harvest date needle loss research has shown that for most of the species tested, growers can reduce needle loss problem by delaying harvest. It has also shown that Canaan fir would be a good species to use to develop a temperature based harvest model because of the dramatic improvement in needle retention that occurs the later this species is harvested. This research has also increased efforts by growers to identify individual trees that do not shed needle, which would then be used to establish grafted seed orchards. This has the potential to significantly improve the quality of trees available to consumers in the future.

Publications

  • Nielsen, U. B. and G. A. Chastagner. 2005. Variation in postharvest quality among Nordmann fir provenances. HortScience 40(3): 553-557. Nielsen, U. B., and G. A Chastagner. Genetic variation in postharvest needle retention among Nordmann fir families and grafted clones. Scand. J. For. Research 20(4): 304-312.


Progress 01/01/04 to 12/31/04

Outputs
Annosus root rot has increased in Christmas tree plantations since the early 1980's. In noble fir plantations, surveys indicated it was present in <4% of the plantations in the early 1980's, compared to 24% of the plantations in 2000. In addition to noble fir, the disease is also killing Fraser fir (which appears to be very susceptible), grand fir, Nordmann fir and Douglas fir in Christmas tree plantations. In all of these situations, these hosts have been planted into sites where a previous crop of Abies was grown. In most all cases the trees were planted next the stumps from the previous rotation. Fraser fir and Nordmann fir appear to represent new host records for the PNW. Mortality data from 20 sites over the past 4 years indicate that in some plantations over 40% of the trees have been killed prior to harvest. Only the S strain of H. annosum has been isolated from trees. In addition, isolates from individual trees in mortality pockets are genetically distinct, indicating that most of the mortality is probably the result of limited spread of the pathogen from many infected stumps in each plantation. Spore trapping studies have indicated that spores are present throughout November and December when trees are being harvested. In addition to killing trees, the presence of staining on harvested trees that have not yet been killed can decrease the postharvest keepability of trees by limiting the amount of water trees can take up during display. Data from three sites where the stumps were removed from a portion of the fields prior to planting indicate that stump removal significantly reduces losses. In the portions of the fields where seedlings were planted next to the stumps, losses have ranged from 10.6 to 20.7%. Stump removal increased the number of harvested trees by 103 to 228 per acre.

Impacts
Annosus root rot has changed many grower practices. Based on the results or this research program, many growers are now using stump treatments at harvest to protect freshly cut stumps from infection and there has also been an increase in stump removal prior to replanting sites.

Publications

  • Antonelli, A., J. Stark, and G. Chastagner, 2004. Christmas tree pest research: Past, present and future. Christmas Tree Lookout 37(3):12-14.
  • Chastagner, G. 2004. Effect of the harvest date on true fir needle retention. Christmas Tree Lookout 37(2):8-10.
  • Chastagner, G. 2004. Stump removal reduces Annosus root rot. Christmas Tree Lookout 37(1):22-25.
  • Chastagner, G.A., U.B. Nielsen, and K.L. Riley. 2004. Comparison of the postharvest quality of noble fir boughs from the United States and Danish provenances grown in Denmark. HortScience 39(3):580-583.
  • Hinesley, E. and G. Chastagner. 2004. Christmas trees: Postharvest quality maintenance guidelines. USDA Handbook on Handling Horticultural Crops. http://www.ba.ars.usda.gov/hb66/contents. html.
  • Hinesley, L.E. and G.A. Chastagner. 2004. Tree care. Amer. Christmas Tree J. 48(5):20-21.


Progress 01/01/03 to 12/31/03

Outputs
The recent appearance of sudden oak death (Phytophthora ramorum) in the Pacific Northwest (PNW) has the potential to significantly impact the Christmas tree and conifer nursery industries in this region. Inoculation trials indicated that P. ramorum infection of Douglas-fir is limited to a period of time just after bud break. Additional studies showed that 20 of 25 conifer species tested were susceptible to P. ramorum and that most of the true firs (Abies spp.) that are commonly grown as Christmas trees are very susceptible to this pathogen. Based on a series of studies with 20 fungicides, it was shown that several systemic and contact fungicides have the potential to protect Douglas-fir seedlings from this disease. Between 2001 and 2003, data collected in 21 commercial Christmas tree plantations in the PNW indicate that mortality associated with Annosus root rot (Heterobasidion annosum) reached almost 40% in some plantations. Spore dispersal studies demonstrated that significant numbers of airborne spores were present in plantations during harvest, which greatly increases the potential for infection of freshly cut stumps. Stump removal prior to replanting significantly reduced the extent of losses caused by this disease. The "S" strain of H. annosum was the only strain of this pathogen detected on noble fir, Fraser fir, Nordmann fir, grand fir, and Douglas-fir Christmas trees in the PNW. In addition to killing trees prior to harvest, studies showed that the staining of stem tissues associated with Annosus root rot reduced the postharvest keepability of cut noble fir Christmas trees. Results from a regional Swiss needle cast (SNC) management project indicate that aerial applications of Thiolux sulfur provided control of SNC in stands of Douglas-fir forest trees. Moisture and needle retention are important factors affecting the postharvest quality of cut Christmas trees. Data collected during a survey of retail lot in Washington, Oregon, California, Rhode Island, Massachusetts, Hew Hampshire, Illinois, and Wisconsin demonstrated that certain types of retail stores do a poor job of minimizing moisture loss from trees on retail lots. Postharvest studies demonstrated that some sources of Douglas-fir from Texada Island, B.C. have significantly better moisture retention than the traditional sources of Douglas-fir grown in the PNW. Cooperative studies were also initiated with cooperators in Michigan, Pennsylvania, New Hampshire, and Nova Scotia to identify sources of balsam fir with superior needle retention.

Impacts
The work on P. ramorum has provided growers with information relating to the potential susceptibility of various conifers to this pathogen, periods of host susceptibility and identified fungicides that are effective in protecting seedlings from this pathogen. As a result of the Annosus portion of this project, growers are much more aware of the importance of this disease and have modified their planting practices to include stump treatment to prevent infection of freshly cut stumps after harvest and stump removal prior to replanting fields where the disease is present. The preliminary data from the Swiss needle cast sulfur trials indicates that sulfur may provide growers with an effective way of controlling this disease in timber stands. The results of the retail lot surveys are being used to develop program to assist growers in their efforts to educate retailers on ways to minimize moisture loss from cut trees on retail lots. The postharvest needle loss experiments have resulted in the identification of specific trees that have superior needle retention. The industry is using this information to establish grafted seed orchards based on the materials that have been tested at WSU Puyallup.

Publications

  • Chastagner, G. A, and K. L. Riley. 2003. Postharvest Quality of noble and Nordmann fir Christmas Trees. HortScience 38(3): 419-421.
  • Chastagner, G. A. 2003. Late season moisture levels of Christmas trees on retail and wholesale lots in Washington, Oregon and California. American Christmas Tree Journal 47(5): 38-40.


Progress 01/01/02 to 12/31/02

Outputs
Historically, Annosus root rot (Heterobasidion annosum) has seldom been a problem in Pacific Northwest Christmas tree plantations. During the past three years, the prevalence of this disease has increased significantly in 2nd and 3rd rotation noble and Fraser fir plantings. During 2001, 19 field plots were established to obtain a better understanding of the association of this disease with tree mortality. About 31,000 trees were examined for above ground symptoms such as branch flagging, wilting, and death. The percentage of symptomatic trees in these plots ranged from 0.3 to 13.6%. If missing and replanted trees were included, the maximum percentage reached 29.9%. H. annosum was associated with 87.8% of the dead and dying trees. Annosus root rot was detected on noble, Fraser, Nordmann, and grand fir, as well as Douglas-fir. Noble and Fraser fir appears to be very susceptible to this disease. These field plots will be monitored during the next several years to determine the level of mortality due to Annosus root rot until all of the trees are harvested from each field. Additional studies were conducted to determine the potential effectiveness of sulfur in controlling Swiss needle cast on Douglas-fir. The 2002 results confirmed the 2001 findings that high rates of sulfur, particularly the Thiolux formulation, have the potential to provide control of SNC comparable to Daconil. However, the 2002 results also indicate that sulfur application may not be as effective as Daconil in limiting the increase of SNC on older age classes of needles. This study suggests that additional research is needed to determine the effectiveness of sulfur applications in limiting the buildup of SNC on older age classes of needles. A three-year-long study examining tree-to-tree variation in needle retention by cut Canaan fir Christmas trees was completed. Ninety-four trees (clones) were tested and results indicated that: needle loss varied by clone and year; there was a high correlation in needle loss rankings among the clones from year to year; only three clones did not shed needles during these tests; 19 clones had <1 % needle loss; and 72 clones had unacceptable levels of needle loss.

Impacts
When completed, the Annosus work will provide growers with information on the relative susceptibility of different Christmas trees to this disease. It will also provide growers with information on the rate of spread of this disease and it's economic impact. Because of this work, growers have already modified their planting practices to include removal of stumps prior to replanting in an effort to minimize the impact of this disease. If sulfur is shown to be effective in controlling Swiss needle cast, this will provide growers with a viable way of controlling this disease in timber stands. The Canaan fir work has identified clones of this species that consistently have superior needle retention. These clones are being used to establish grafted clonal seed orchards in an effort to improve the quality of Canaan fir Christmas trees.

Publications

  • Chastagner, G. A. 2002. Advanced Research Update. Christmas Tree Lookout 35(2): 26-30.
  • Chastagner, G. A. 2002. Fungicidal management of Swiss needle cast. pp. 65-69. In: G. Filip (Ed.) Swiss Needle Cast Cooperative Annual Report, November 2002, Oregon State University, 86 p.
  • Chastagner, G. A., I. M. Thomsen, J. Hudak, and K. L. Riley. 2002. Heterobasidion annosum associated with mortality of Christmas trees in the Pacific Northwest. Phytopathology 92: S14
  • Chastagner, G. S., and J. Hudak. 2002. Root diseases associated with dead and dying noble fir Christmas trees in the Pacific Northwest. Phytopathology 92: S14.
  • Catal, M., G. C. Adams, and G. A. Chastagner. 2002. Detection, identification and quantification of latent needlecast pathogens and endophytes in symptomless conifer foliage by PCR and Dot-blot assays. pp 164-178. In: Utoila, A. and V. Ahola. (eds.) Shoot and Foliage Diseases in Forest Trees, Finish Forest Research Institute, Research Papers 829, 201 p.
  • Chastagner, G. A. 2002. Christmas tree freshness -Making it a priority. The Real Tree Line 42(4):13, 16.


Progress 01/01/01 to 12/31/01

Outputs
Annosus root rot, caused by Heterobasidion annosum, has become a major problem in some noble and Fraser fir Christmas trees plantations in the Pacific Northwest (PNW). A survey in 2000, showed that this disease now occurs in about 20 percent of the noble fir plantations in Washington and Oregon and is killing up to 30% of the trees in some plantations. A series of 18 field plots were established during 2001 to examine the rate of spread of this disease and assess the effectiveness of stump treatments and stump removal in the management of this disease. Rhabdocline needle cast limits the production of intermountain sources of Douglas-fir Christmas trees in the PNW. These sources of Douglas-fir have better moisture retention and are more tolerant to subfreezing temperatures than the coastal types of Douglas-fir that are currently grown. Identification of intermountain sources of Douglas-fir that are resistant to this disease has the potential to improve the quality of Douglas-fir trees available to consumers, particularly in cold weather markets. Using a planting of intermountain sources of Douglas-fir at WSU Puyallup, we have shown that it is possible to reliably detect, identify and quantify levels of Rhabdocline infection in symptomless foliage of Douglas-fir using DNA-based PCR molecular probes. These studies have also shown that intermountain Douglas-fir from the Clearwater National Forest in Idaho have excellent resistance to Rhabdocline needle cast. Work in Denmark has identified a number of potential sources of fast growing Nordmann fir trees that have improved needle retention. Seed has been obtained from two tested Danish stands and five Danish clones for testing in the PNW. In addition, seed has also been obtained from 9 additional stands of Nordmann fir in Georgia and Turkey and five stands of Turkish fir in Turkey for testing in the PNW.

Impacts
This research will provide growers with information that will allow them to effectively manage diseases that can limit the production of high quality trees. It has also identified sources of high quality Nordmann fir that growers can potentially grow in the PNW.

Publications

  • Chastagner, G. A. 2001. Needle Casts. Pp. 678-682. In: O. C. Maloy and T. D. Murray (Eds.) Encyclopedia of Plant Pathology. John Wiley and Sons, Inc.
  • Chastagner, G. A. 2001. Poplar diseases. Pp. 308-316. In: Diseases of Woody Ornamentals and Trees in Nurseries. R. L. Jones and D. M. Benson (Editors). APS Press, St. Paul, MN.
  • Antonelli, Art, Stark, John, and Chastagner, Gary. 2001. Acetamiprid: Another possibility for controlling Colley Spruce gall adelgids. Christmas Tree Lookout 34(3): 32-35.
  • Antonelli, Art, Stark, John, and Chastagner, Gary. 2001. Now: The never-before-told story of the mysterious mite. Christmas Tree Lookout 34(3): 37
  • Antonelli, Art, Stark, John, and Chastagner, Gary. 2001. So, you believe root aphids are the problem. Maybe not. Christmas Tree Lookout 34(3): 26-29.
  • Catal, M., Adams, G. C., and Chastagner, G. A. 2001. Detection, identification and quantification of Rhabdocline infection in symptomless foliage of Douglas-fir. Phytopathology 91: S13
  • Chastagner, G. A and C. G. Landgren. 2000. A brief overview of previous Western North America Christmas tree research and extension conferences. Pp. 9-10. In: C. J. Christensen (Ed.)Improvements in Christmas tree and greenery quality. Skov & Landskab Report No. 7. Danish Center for forest, Landscape and Planning. Horsholm, DK., 124 pp.
  • Chastagner, G. A and K. L. Riley. 2000. An overview of the postharvest characteristics of different Abies spp grown as Christmas trees. Pp. 74-79. In: C. J. Christensen (Ed.)Improvements in Christmas tree and greenery quality. Skov & Landskab Report No. 7. Danish Center for forest, Landscape and Planning. Horsholm, DK., 124 pp.
  • Chastagner, G. A and K. L. Riley. 2000. Diseases that limit the production of noble fir Christmas trees in the Pacific Northwest. Pp. 13-21. In: C. J. Christensen (Ed.)Improvements in Christmas tree and greenery quality. Skov & Landskab Report No. 7. Danish Center for forest, Landscape and Planning. Horsholm, DK., 124 pp.
  • Chastagner, G. A, and U. B. Nielsen. 2001. Identification of Danish sources of Nordmann and noble fir with superior postharvest Christmas tree chacteristics. USDA FAS/ICD/RESD/SCP Final Research Report for Project DA08, 53 pages.
  • Chastagner, G. A. 2001. Fir Diseases. Pp. 152-156. In: Diseases of Woody Ornamentals and Trees in Nurseries. R. L. Jones and D. M. Benson (Editors). APS Press, St. Paul, MN
  • Chastagner, G. A. 2001. Highlights of the international conference in Denmark. American Christmas Tree Journal 45(2): 39
  • Chastagner, G. A. 2001. Susceptibility of intermountain Douglas-fir to Rhabdocline needle cast when grown in the Pacific Northwest. Online. Plant Health Progress doi:10.1094/PHP-2001-1029-01-RS.
  • Chastagner, G. A. 2001. Susceptibility of intermountain provenances of Douglas fir to Rhabdocline needle cast. Phytopathology 91: S182
  • Chastagner, G. A. and K. Riley. 2001. Water holding capacity of Christmas tree stands. American Christmas Tree Journal 45(5): 26-30.
  • Chastagner, G. A., and K. Riley. 2000. Susceptibility of intermountain provenances of Douglas-fir to Rhabdocline needle cast. Pp. 68-71. In: C. J. Christensen (Ed.)Improvements in Christmas tree and greenery quality. Skov & Landskab Report No. 7. Danish Center for Forest, Landscape and Planning. Horsholm, DK., 124 pp.
  • Chastagner, G. A., and Riley, K. L. 2001. An overview of postharvest characteristics of different Abies spp. grown as Christmas trees. Christmas Tree Lookout 34(2): 18-23.
  • Chastagner, G. A., U. B. Nielsen and K. L. Riley. 2000. The use of detached branches to identify sources of Nordmann fir with superior needle retention characteristics. Pp. 26-32. In: C. J. Christensen (Ed.)Improvements in Christmas tree and greenery quality. Skov & Landskab Report No. 7. Danish Center for Forest, Landscape and Planning. Horsholm, DK., 124 pp.
  • Chastagner, G. and J. Stone. 2001. Fungicidal control of Swiss needle cast in stands of Douglas-fir timber. Pp. 89-95. In: G. Filip, Editor. Swiss Needle Cast Cooperative Annual Report. 98 pp.
  • Nielsen, U. B., C. J. Christensen, and G. A Chastagner. 2001. Efter-host kvalitet: Effekt af traeart, proveniens or godskning i nordmannsgran. Pp 89-95. In: Skov & Landskabskonferencen 2001, Nyborg, DK, 213 pages, Center for Skov, Landskab og Planlaegning, Horsholm, DK
  • Stone, J., P. Reeser, W. Sutton, and G. Chastagner. 2001. Sulfur fungicide studies. Pp. 84-88. In: G. Filip, Editor. Swiss Needle Cast Cooperative Annual Report. 98 pp.