Control of Phytophthora, Pythium and Other Root Health Problems Affecting Floral Crops
Agreement # 58-1907-0-0035
ADODR: Wraight, Stephen - Ithaca, New York, Plant Protection Research
Principal Investigator: Daughtrey, M. - Cornell University
Objectives: The objectives of this cooperative research project are to: 1) Identify the major Phytophthora spp. affecting floriculture production and determine which aspects of Phytophthora's life history contribute significantly to control failure; 2) Determine the role of environment in the disease cycles of Botrytis and Sphaceloma and investigate environmental manipulation as a viable disease management tool; 3) Develop durable production strategies for preventing and eliminating disease caused by Phytophthora, Botrytis, and Sphaceloma spp. on floriculture hosts; 4) Screen novel agents for their potential as management tools for control of Phytophthora, Botrytis, and Sphaceloma spp.; 5) Isolate, identify and screen natural plant extracts for deer and rabbit repellency; and 6) Develop effective, persistent, non-phytotoxic formulations of these repellents for treatment of ornamental plants.
Approach: Project objectives will be achieved through a teamwork approach, bringing together skills of plant and insect pathologists, a plant physiologist and entomologists. Phytophthora and Pythium populations will be sampled in diverse greenhouse systems, and morphological, cultural and other methods will be used to define populations in the greenhouse environment and in flower crops. Effective control measures will be sought for water mold populations in general, and for fungicide-resistant populations in particular, utilizing multiple strategies to reduce survival and spread of the pathogens within a greenhouse. Research on physiological disease prevention in lilies will focus on determining the etiology of leaf scorch in Oriental hybrid lilies and establishing a cultural system for its prevention, as well as determining postharvest conditions preventing poor performance of bulb crops.
Major Accomplishments over the life of the project: Pathogen Identification and Tracking: A number of molecular methods, including PCR/RFLP, AFLP, inter simple sequence repeats (ISSR), fatty acid methyl ester (FAME) analysis, and ribosomal DNA sequencing, were developed for identification of oomycete pathogens of greenhouse and nursery crops, and efficiencies of the various methods were compared. The PCR/RFLP method was found to be labor intensive, and was abandoned in favor of other methods. This research has provided the methods that are now being used for rapid identification and tracking of pathogen populations in floriculture research and commercial production facilities.
Genetic markers, including the DNA sequence of the ITS region of ribosomal DNA (rDNA), were established to identify Pythium species from infected crops and various areas within greenhouses. ITS-1 and -2 region ribosomal DNA and ras-related protein gene sequences of many of the Pythium species encountered in this work were deposited in the National Center for Biotechnology Information (NCBI) database (GenBank; http://www.ncbi.nlm.nih.gov/BLAST/) and are thus available to all researchers for use in the identification of Pythium species.
The three most frequently encountered Pythium species causing crop losses in the greenhouse were found to be Pythium irregulare, P. ultimum, and P. aphanidermatum. Isolates of P. aphanidermatum were discovered to have extremely few DNA sequence differences, regardless of their geographic origin. DNA fingerprinting techniques (AFLP) and fatty acid methyl ester (FAME) analysis (previously used for identifying bacteria) were developed for rapid identification of important Phytophthora species collected from greenhouses and nurseries (Phytophthora cactorum, P. cinnamomi, P citricola, P. citrophthora, P. cryptogea and P. nicotianae).
Fungicide Resistance Detection and Characterization: Fungicide-resistant pathogen populations were identified in greenhouses. This included the first report of resistance to propamocarb and multiple resistance to propamocarb and mefenoxam in an Oomycete. Identification of a high level of mefenoxam/metalaxyl resistance in flower crop greenhouse Pythium populations has underscored the need for grower education to reduce over-reliance on this chemistry and for trials of alternative products and methods to improve disease management. Highly mefenoxam‑resistant strains of Pythium were detected in greenhouse water-holding tanks, suggesting that irrigation system holding tanks could provide a reservoir of resistant strains.
Phytophthora drechsleri has been identified as an emerging problem on poinsettias. Good control of P. drechsleri on poinsettia was demonstrated for Biophos, BAS 500, Heritage 50WDG, Ardent 50WP, EXP 10623, Aliette 80WDG, Truban 30WP, and Banol FL. SubdueMAXX was not as effective, possibly due to mefenoxam resistance in the P. drechsleri strain tested. Mefenoxam resistance in Phytophthora nicotianae was reported for the first time from woody ornamental crops in the Eastern United States.
Upper Leaf Necrosis (ULN) Cause and Control: ULN is a physiological disorder of a specific group of lilies, the so-called "oriental hybrid" types. Data were generated supporting the hypothesis that this disorder is one of calcium deficiency that develops in young leaves as they expand. Studies of leaf calcium content, exacerbation of symptoms by growing plants in the absence of calcium, and reduction of symptoms by cultural conditions that increase calcium movement to young leaves are three major pieces of evidence that have linked calcium to this problem. These studies have stimulated several lines of research aimed at providing practical solutions to this disease problem.
Alternatives to Foramaldehyde for Disease Control: Chlorine dioxide had been demonstrated to be a useful alternative to formaldehyde for control of flower bulb diseases.
Science and/or technologies transferred:
Chastagner: Organized two half-day programs for ornamental bulb crop growers during the Western Washington Horticulture Association Conference in Seattle, Washington on January 9-10, 2003. Information relating to the potential use of chlorine dioxide and new reduced risk fungicides to manage soilborne diseases and postharvest bulb diseases was presented to 25-30 growers in attendance at this meeting.
Chastagner: Organized a WSU Bulb Grower's Field Day at Puyallup, Washington on May 14, 2003. Approximately 30 growers from Washington, Oregon and British Columbia attended this event. Growers were able to see a number of field and greenhouse trials relating to the use of chlorine dioxide and reduced risk fungicides to control bulb and soilborne diseases of ornamental bulb crops.
Sensenbach, Hoebeke, Sanderson, Wraight: The habits and identifying characteristics of the hunter fly, Coenosia attenuata, have been published in the scientific literature (paper listed in report for CRIS project 1907-22000-016-00D and related to growers at greenhouse pest management workshops to promote establishment and conservation of this beneficial predator.
Chastagner: Continued to work with a company that is developing controlled release technologies for the delivery of chlorine dioxide gas as a commercially available product that will allow growers to expose ornamental bulbs to specified concentrations of chlorine dioxide gas during storage. The commercial development of this product will depend in large part on the result of our ongoing research.
Chastagner, Daughtrey: Data relating to the effectiveness of various reduced risk fungicides in controlling bulb and soilborne diseases is being used by the IR-4 program and various chemical companies to support the registration of some of these new products for use on flower bulb and flowering potted plant crops.
ITS-1 and -2 region ribosomal DNA and ras-related protein gene sequences of many of the Pythium species encountered in this work have been deposited in the National Center for Biotechnology Information (CBI) database (GenBank; http://www.ncbi.nlm.nih.gov/BLAST/) and are thus available to all researchers for use in the identification of Pythium species.
Information on the effectiveness of chlorine dioxide in preventing the spread of Fusarium basal rot during the hot water treatment of bulbs and the effects of chlorine dioxide gas on the germination of pathogen spores has been exchanged with three commercial companies (two in the United States and one in South Africa) that supply chlorine dioxide treatment equipment, as well as to other scientists and numerous growers. One of the U.S. companies has used this information to convert a formaldehyde-based hot water treatment facility at one grower's farm to a chlorine dioxide based system. This past spring, the South Africa company established a series of on-farm trials with several growers in the Netherlands to determine the potential benefits of this technology in managing bulb diseases under Dutch production systems.
A company that develops controlled release technologies for the delivery of chlorine dioxide gas is using the Washington State data to continue work on the development of a product that will allow growers to expose ornamental bulbs to specified concentrations of chlorine dioxide gas during storage. The commercial development of this product will depend, in large part, on the result of our ongoing research.
Washington State and Cornell data on the effectiveness of various reduced risk fungicides in controlling bulb and soilborne diseases on flower bulb crops, as well as diseases of greenhouse grown potted plants is being used by various chemical companies to support the registration of some of these new products. Some of the data is being used by the IR-4 program as well.
In the past year, a number of formal and informal research "open houses" have been held at the Cornell research lab and greenhouse facility where work on lily leaf necrosis is conducted. Scientists and extension personnel, greenhouse producers, U.S. bulb distributors, off-shore bulb producers and bulb exporters have all attended these field days, with an estimated 250+ people taking part. Portions of the information developed can be applied immediately on a trial basis in the greenhouse industry.
A number of the findings reported here have already been incorporated into specific recommendations for greenhouse and nursery crop disease management. For example, identification of emerging fungicide resistance problems has led to refinements of Phytophthora control recommendations (especially with regard to selection and rotation of fungicides used against P. nicotianae in nurseries producing woody ornamentals) and to specific warnings regarding the potentially disastrous consequences of failing to diligently clean irrigation water systems.
Publications in the Popular Press:
Becktell, M., Daughtrey, M., Fry, W.E. Beware of late blight on petunias and tomatoes. Greenhouse Business. 2003 v. 9(6). p. 31-32.
Burns, J., Daughtrey, M. Diseases that occur during early stages of poinsettia production. Northeast Greenhouse IPM Notes. 2002. v. 8(12). p. 1-2.
Daughtrey, M., Rathbone, M. Petunia Late Blight, an Emerging Disease? Long Island Horticultural News. 2002. November. p. 1.
Daughtrey, M., Rathbone, M. Scary New Phytophthoras. GrowerTalks. 2002. v. 66(5). p. 90-92.
Presentations to Growers:
Becktell, M., Daughtrey, M., Fry, W. Petunia late blight: serious disease or Typhoid Mary? Ohio Florists Association International Short Course, Columbus, Ohio. 2003.
Chastagner, G. Management of soil borne fungal disease in ornamental bulb crops and the potential use of chlorine dioxide gas to control bulb diseases. Western Washington Horticulture Association Conference. Seattle, WA. January, 2003.
-Summary of results from chlorine dioxide research. Western Ornamentals & Turf Disease Conference. Portland, OR. January, 2003.
-Effects of chlorine dioxide gas on germination of pathogen inocula. Annual Meeting, American Phytopathological Society, Pacific Division. Kona, Hawaii. June, 2003.
Daughtrey, M. Research on diseases of greenhouse crops. Long Island Horticultural Research & Extension Center Open House, Riverhead, NY, September, 2002.
-Sudden oak death and other Phytophthora threats. Long Island Agricultural Forum. January, 2003.
Eisenmann, J., Jeffers, S. Phytophthora species: Pathogens of herbaceous ornamental crops. South Carolina Horticulture Industry Seminars and Trade Show. Myrtle Beach, SC; February, 2003.
-Phytophthora nicotianae: A pathogen of herbaceous ornamental plants. Southern Nursery Association Research Conference. 2003.
Jeffers, S. Fungicides for commercial ornamental crops. Southeast Greenhouse Conference and Trade Show. Greenville, SC. June, 2003.
-Fungus diseases on the foliage of greenhouse crops: diagnosis and management. Southeast Greenhouse Conference and Trade Show. Greenville, SC. June 2003.
Moorman, G. Powdery mildew and Pythium, two major problems in greenhouse production. 2002 Somerset Fall Greenhouse Meeting. Berlin, PA.
-Disease identification and management in the greenhouse. Greenhouse Management Short Course. Altoona, PA.
-Powdery mildew and Pythium root rots in the greenhouse. Tri-County Vegetable/Greenhouse Meeting. Shippensburg, PA.
Sensenbach, E., Wraight, S., Sanderson, J. The "hunter fly", a new greenhouse predator. Cornell Greenhouse Open House & Field Day, Ithaca, NY. August, 2003.
Presentations to Scientists:
Becktell, M., Daughtrey, M., Fry, W. Temperature and moisture requirements for establishment, incubation period, latent period and sporulation of Phytophthora infestans on petunia. American Phytopathological Society annual meeting, Charlotte, NC. August, 2003.
Daughtrey, M., Jeffers, S. Phytophthora research studies. Floral and Nursery Research Initiative Workshop, Raleigh, NC. March, 2003.
Eisenmann, J., Jeffers, S. Phytophthora nicotianae: A pathogen of herbaceous ornamental plants. Southern Nursery Association Research Conference, Atlanta, GA. July, 2003.
Eisenmann, J., Schnabel, G., Jeffers, S. Characterization of two papillate species of Phytophthora from ornamental plants. American Phytopathological Society Annual Meeting, Charlotte, NC. August, 2003.
Garzon, C., Geiger, D., Moorman, G. AFLP as a tool for identification and characterization of Pythium species. Invited presentation. Eastern Regional Conference on the Ecology of Root-Infecting Microorganisms, Williamsburg, VA. 2002.
Garzon, C., Geiger, D., Moorman, G. AFLP as tools for characterization of Pythium species. Invited presentation. Cornell University Dept. Plant Pathology, Geneva, NY. 2002.
Garzon, C., Geiger, D., Moorman, G. Species identification and population analysis of Pythium species using AFLP markers. Fungal Genetics Meeting, Asilomar, CA. 2003.
Jeffers, S. Fungicides for managing Phytophthora species in nurseries. American Phytopathological Society: Sudden Oak Death-How Concerned Should You Be? An International Online Symposium. http://sod.apsnet.org/Papers/Jeffers/default.htm. 21 April - 12 May, 2003.
-Isolation & detection of Phytophthora spp. 13th Ornamental Workshop on Diseases and Insects, Crossnore, NC. October, 2002.
-Phytophthora species: Pathogens of trees and shrubs. Southeast Forest Pathology Workshop: --Diseases and Symbiotic Fungi of the Forest Ecosystem in the Southern Appalachian Mountains. Biological Research Station, Highlands, NC. October, 2002.
Moorman, G. Propamocarb resistance in species of Pythium. American Phytopathological Society annual national meeting. Milwaukee, WI. 2002.
Pulas, C., Jeffers, S. Morphological variation in Phytophthora citricola-a plant pathogenic fungus.1st SC LIFE Colloquium of Undergraduate Research. Benedict College, Columbia, SC. April, 2003.
Ramon, M., Moorman, G. Effects of fertilizer, pH, and biological control on Pythium root rot. American Phytopathological Society, Northeastern Division. Bromont, Quebec, Canada. 2002.
Sensenbach, E., Wraight, S., Sanderson, J. Coenosia attenuata as a predator of fungus gnats. USDA/ARS Floriculture & Nursery Research Initiative Researchers Meeting, Raleigh, NC. March, 2003.
Publications in the Popular Press/Extension Articles:
Daughtrey, M. Managing diseases on bedding plant crops. Country Folks Grower. 2002. v. 11(3). p. 22-23.
Daughtrey, M. Studying Phytophthora foes of floral crops. Greenhouse Product News. 2002. v. 12(6). p. 44-45.
Moorman, G.W., Daughtrey, M.L. Don't expect Pythium root rot to always act the same. Greenhouse Product News. 2002. v. 12. p. 36-38.
Moorman, G.W., Daughtrey, M.L. 2001. Pythium on the rise. GrowerTalks. 2001. v. 65. p. 104-108.
Presentations to Organizations:
Chang, Y-C. Upper leaf necrosis. Fred C. Gloeckner Foundation Board of Directors, Ithaca, NY, May 2002.
Chastagner, G. Potential use of chlorine dioxide to control diseases in ornamental plant production systems. Invited presentation at the Western Region International Plant Propagators' Society Annual Meeting. Seattle, WA. September, 2001.
Chastagner, G. Effects of chlorine dioxide gas on the germination of fungal spores. Northwest Bulb and Cut Flower Conference. Seattle, WA. November 2001.
Chastagner, G. Management of soil borne fungal disease in ornamental bulb crops. Northwest Bulb and Cut Flower Conference. Seattle, WA. November 2001.
Chastagner, G. The effectiveness of chlorine dioxide gas in killing spores of several plant pathogens. Ornamental and Turf Disease Conference. Portland, OR. January 2002.
Chastagner, G. Update on research utilizing chlorine dioxide gas to control diseases on ornamental bulb crops. WSU Bulb Grower's Field Day. Mount Vernon, WA. May 2002.
Daughtrey, M. Controlling Diseases of Greenhouse Flower Crops. Kansas Greenhouse Growers. Manhattan, KS. October 2002.
Daughtrey, M. Diseases of Bedding Plant Crops. Albany Bedding Plant School. Latham, NY. January 2002.
Daughtrey, M. New and Emerging Diseases. Society of American Florists' Pest Management Conference. San Diego, CA. February 2002.
Daughtrey, M. National Floriculture Research Sponsored by the Floriculture & Nursery Research Initiative. Society of American Florists. Washington, DC. March 2002.
Daughtrey, M. Diseases of Greenhouse Crops. Alberta Horticulture Congress. Edmonton, AB, Canada. November 2001.
Jeffers, S.N. Potential use of fatty acid methyl ester (FAME) analysis for identifying species of Phytophthora from ornamental crops. Eastern Regional Conference on the Ecology of Root-Infecting Microorganisms (ERCERIM). Williamsburg, VA. March 2002.
Miller, W.B. Research Update. North American Flowerbulb Wholesaler's Association. Ithaca, NY. March 2002.
Miller, W.B. Combating Upper Leaf Necrosis. Ohio Florist's Association Shortcourse. Columbus, OH. July 2002.
Moorman, G.W. Pythium identification. Mid-Atlantic Fruit and Vegetable Convention. Hershey, PA. 2001.
Moorman, G.W. Where pathogens come from in greenhouse production. Southeast Greenhouse Conference. Greenville, SC. 2001.
Moorman, G.W. Managing Botrytis and Pythium fungicide resistance in the greenhouse. Southeast Greenhouse Conference. Greenville, SC. 2001.
Knoedler, J., Daughtrey, M. The presence and distribution of Pythium and Phytophthora in greenhouses. 2000 Annual Report, Long Island Horticultural Research & Extension Center, Cornell University. Riverhead, New York. 2000. p. 16.
Daughtrey, M., Knoedler, J. Instances of fungicide resistance in Pythium and Phytophthora in greenhouses. 2000 Annual Report, Long Island Horticultural Research & Extension Center, Cornell University. Riverhead, New York. 2000. p. 20.
Moorman, G.W. Biology of Pythium root rot. American Floral Endowment Special Research Report #103: Disease Management. 2000. 2 p.
"Disease Management of Flowering Annuals" presented by M. Daughtrey. ProGreen Expo. Denver, Colorado. January 3, 2001.
"Best Management Practices for Disease Control in Nurseries" presented by M. Daughtrey. Long Island Horticulture Conference. Ronkonkoma, New York. February 7, 2001.
"Managing Soil Fungi that Cause Root Disease" presented by M. Daughtrey. Nassau-Suffolk Landscape Gardeners Association Conference. Huntington, New York. March 7, 2001.
"Disease Management in Perennial Production" presented by M. Daughtrey. Ohio Florists Short Course. Columbus, Ohio. July 18, 2001.