Progress 10/01/06 to 09/30/09
Outputs
OUTPUTS: Experiments directed at improving control methodology for downy mildew and powdery mildew diseases of greenhouse flower crops were conducted at the Long Island Horticultural Research and Extension Center (LIHREC) over a three-year period. In two greenhouse trials, cultivars of verbena were compared for susceptibility to the powdery mildew Podosphaera xanthiii, which causes losses of sales for verbenas grown as spring bedding plant crops and also attacks squash transplants. In year one, 23 cultivars were compared and in year two, 33 cultivars were observed. These replicated and statistically analyzed trials allowed comparison of verbenas from five different propagation companies rated under uniform environmental conditions. Powdery mildew disease control trials with experimental and registered fungicides and biofungicides were undertaken for three years, focusing at various times on the management of diseases of gerbera, verbena, dahlia and poinsettia. A greenhouse experiment tested biological and biorational control treatments in various rotations for their ability to protect rosemary plants from powdery mildew during greenhouse production. This herb is difficult to produce because of its vulnerability to powdery mildew and the scarcity of powdery mildew control materials registered for use on herbs in the greenhouse. For poinsettias, also very vulnerable to a powdery mildew (Oidium sp.), a biological control program was evaluated in comparison to a fungicide program using new reduced-risk fungicides. Control of coleus downy mildew, a relatively new disease that causes leaf spotting and curling as well as leaf drop of coleus plants in greenhouse production and in garden beds, was studied in three replicated experiments that evaluated experimental and registered fungicides, including reduced-risk materials. To look for evidence of seed transmission of the Peronospora sp. causing the disease, seeds of 23 coleus cultivars were planted and grown under conditions suitable for downy mildew development. Another coleus trial tested 49 cultivars for resistance to downy mildew by observing summer landscape performance of plants inoculated with downy mildew during spring in the greenhouse. These research studies have been highlighted annually in presentations at the LIHREC Plant Science Day, as well as in talks given at regional, state and national conferences attended by greenhouse growers and the allied tradespeople. Disease management recommendations for downy mildew and powdery mildew are frequently provided to growers on an individual basis, along with diagnoses. Information developed has also been disseminated via web sites, podcasts, trade journal articles, and scholarly publications. PARTICIPANTS: Margery Daughtrey. co-principal investigator, has supervised and done on-site planning of the experimentation at Cornell's Long Island Horticultural Research and Extension Center in Riverhead, NY. George Hudler, co-principal investigator, has helped to plan some of the studies and provided commentary on their analysis. Technical expertise for experimental establishment, maintenance, data collection and analysis has been provided by research technician Maria Tobiasz. Research support specialists Jadwiga Komorowska-Jedrys and Genevieve Giroux have also helped with the experiments. Studies on powdery mildew and downy mildew have been done in collaboration with Mary Hausbeck, Michigan State University, with joint funding provided by the American Floral Endowment. Chemical companies have contributed material and sometimes financial support, including Natural Industries, Valent, OHP, Syngenta, BASF, and Bioworks. Plant propagation companies and local growers have supplied plant materials, including Dummen USA, Ball Horticultural, Paul Ecke Ranch, Syngenta Plants, Kurt Weiss, Inc., Ivy Acres, Inc., and Van Bourgondien Greenhouses, Inc. Training has also been provided through the New York State Nursery and Landscape Association's Certified Nursery and Landscape Professional Program and through the New York State Master Gardener Program on the topics of this research. TARGET AUDIENCES: The primary target audience for this research is the commercial producers of greenhouse flower crops in the United States. This group includes specialist propagators concerned with developing and maintaining clean stock for plant propagation, rooting stations, and growers who finish the crops for sale, many of them small businesses. Retail garden centers, botanical gardens, public gardeners for municipalities, landscapers, Master Gardeners and other private gardeners have also been given information. Dozens of presentations have been made annually to these groups, at venues including the OFA Conference, the New England Greenhouse Conference, the Society of American Florists Pest Management Conference, the Cornell Floriculture Conference, Connecticut Perennials Conference, the Long Island Floriculture Conference, Long Island Agricultural Forum, Capital District Bedding Plant School, Hudson Valley Greenhouse and Nursery Conference, Long Island Chrysanthemum Field Day, Master Gardener Training, Certified Nursery and Landscaper Training, and the Long Island Horticultural Research and Extension Center Plant Science Day. Articles have appeared in industry trade magazines including Greenhouse Product News and GrowerTalks, and podcasts have been presented through the Greenhouse Grower Floricast website. Articles have also been published in Plant Disease and presented at plant pathology society meetings to deliver information to the scientific community. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
New information discovered through our powdery mildew research has been valuable to verbena propagators and growers. Disease outbreaks have been observed to be less common in the past two years; if this trend continues it might indicate that heightened awareness of the disease and more careful cultivar choices at all levels of production have reduced the powdery mildew problem in the industry. Less prevalent powdery mildew means that growers can scout for the disease rather than using fungicides preventively. At least one verbena cultivar that we identified as highly susceptible to powdery mildew has been taken off the market. Growers surveyed have indicated that they have made decisions about which cultivars to grow based on our data. Extremely low susceptibility to powdery mildew was identified in some Superbena cultivars (Coral, Dark Blue, Large Lilac Blue, Pink Shades and Purple), Lanai cultivars (Blue 08, Deep Purple, Purple Star, and Red 07), Aztecs (Dark Red and Violet), Rapunzel Lilac and Lascar White. Thus growers wishing to produce verbenas without fungicides now have good choices. It is hoped that plant breeders will use this data to develop new disease-resistant cultivars. Our studies on coleus downy mildew have shown that cultivars are almost all susceptible, but that symptom intensity varies. Some showed such strong leaf curling and spotting that landscapers will not want to use them in gardens. We have not obtained evidence of seedborne downy mildew in our experiments, but because grower experience suggests that this occurs, further studies are needed. Data developed on fungicide performance is being used by growers when making their management decisions, as well as by the agrichemical companies as they refine product formulations and rates for safe and effective performance on greenhouse crops. Fungicide use during coleus production is needed for downy mildew control: studies have shown strong efficacy of Stature SC (at the high labeled rate), SubdueMAXX, Fenstop and Dithane, and some benefit of strobilurins including Heritage and Disarm, but little benefit from Aliette. Although Phyton 27 was effective against downy mildew, treated coleus showed some foliar injury. For control of powdery mildew on gerberas, the standard fungicide Terraguard and the newly registered Pageant were shown to be very effective at 8 oz per 100 gal. For poinsettias, Insignia and Phyton 27 have both shown ability to protect against powdery mildew, while Endorse showed similar effectiveness but high residue. Insignia has shown good effectiveness on dahlia powdery mildew as well. The biofungicide Actinovate SP was shown to have utility for powdery mildew management in poinsettias, but results indicate that it will need to be integrated into a program with other fungicides if disease pressure is high. For rosemary powdery mildew control, organic programs using Milstop at 3 lb per 100 gal or UltraFine oil at 0.5 percent were effective at a 7-day interval alone or in programs alternating with Cease at 6 qts per 100 gal.
Publications
- Chase, A. R. and Daughtrey, M. 2009. This month in diseases: poinsettias. Greenhouse Product News 19 (8): 14.
- Chase, A. R and Daughtrey, M. 2009. This month in diseases: pansies. Greenhouse Product News 19 (9): 12.
- Chase, A. R. and Daughtrey, M. 2009. This month in diseases: crucifers. Greenhouse Product News 19 (10): 14.
- Daughtrey, M. 2009. Finding powdery mildew in the greenhouse. Floricast. Greenhouse Grower, Meister Publishing. http://www.greenhousegower.com/ggtv/cid=2
- Daughtrey, M. and Tobiasz, M. 2009. Comparison of verbena cultivars for susceptibility to powdery mildew, 2008. 2008 Annual Report, L. I. Horticultural Research & Extension Center, Cornell University, Riverhead, NY, p. 39.
- Daughtrey, M. and Tobiasz, M. 2009. Tests of V10161, Fenstop and Stature DM for control of downy mildew on coleus. 2008 Annual Report, L. I. Horticultural Research & Extension Center, Cornell University, Riverhead, NY, p. 42.
- Daughtrey, M. and Tobiasz, M. 2009. Downy mildew trials on coleus-using experimental fungicides, Heritage and Stature DM. 2008 Annual Report, L. I. Horticultural Research & Extension Center, Cornell University, Riverhead, NY, p. 42-43.
- Daughtrey, M. and Tobiasz, M. 2009. Fungicides for control of powdery mildew on gerbera. 2008 Annual Report, L. I. Horticultural Research & Extension Center, Cornell University, Riverhead, NY, p. 43-44.
- Daughtrey, M., Tobiasz, M., Komorowska-Jedrys, J. and Giroux, G. 2009. Diagnosis of diseases on greenhouse flower crops in 2008. 2008 Annual Report, L. I. Horticultural Research & Extension Center, Cornell University, Riverhead, NY, p. 87.
- Jancovics, T., Kiss, L., Niks, R. E. and Daughtrey, M. L. 2009. First report of powdery mildew (Oidium sp.) on pincushion flower (Scabiosa columbaria) in New York. Plant Disease 93:316.
- Gleason, M., Daughtrey, M., Chase, A., Moorman, G. and Mueller, D. 2009. Diseases of Herbaceous Perennials. APS Press, St. Paul, 300 pp.
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Progress 10/01/07 to 09/30/08
Outputs
OUTPUTS: Activities in this reporting period focused on the prevention of powdery mildew and downy mildew diseases affecting commercial flower crops. One experiment compared twenty-three cultivars of verbena for susceptibility to the powdery mildew Podosphaera xanthii, which is commonly very problematic for bedding plant growers. The percentage of foliage covered with powdery mildew was evaluated three times during July. Another replicated trial was conducted to evaluate experimental and registered fungicides for control of a relatively new downy mildew, Peronospora sp., that causes leaf spotting, leaf curl, and leaf drop on coleus. Management of powdery mildews was investigated in three separate experiments addressing these diseases on gerbera, verbena and poinsettia in the greenhouse. Each of these powdery mildew diseases causes significant crop losses every year. Data collected in these trials were statistically analyzed. New knowledge was generated by the experimentation and immediately shared with those who would benefit from the information. Events such as the Plant Science Day for commercial growers held at the Long Island Horticultural Research and Extension Center (LIHREC) and cooperative extension sponsored meetings for floriculturists across New York provided venues in which the results of these experiments were communicated in presentations to growers. Experimental results assisted growers in their pest management decisions. Plant companies producing verbena were contacted directly with the results of the cultivar comparison trial, in order that information on disease susceptibility could be incorporated into plant breeding and marketing decisions. Manufacturers of plant protection materials were provided with data on performance, residue, and phytotoxicity to aid in the development or refinement of product labels. Dissemination of information at the national level to guide growers in skillful pest management for downy and powdery mildews was achieved through articles in greenhouse trade magazines describing research results. Summaries of experimental results were also posted at the LIHREC website to provide growers and other scientists worldwide access to the information. Results have also been published to provide a permanent record in the scientific literature. PARTICIPANTS: The Principal investigators, Margery Daughtrey and George Hudler, planned the objectives and the experimentation and directed the work. Maria Tobiasz, research technician, provided technical expertise for treatment application and data collection and analysis. Partner organizations included companies that provided plant materials: Ball FloraPlant, Dummen USA, Proven Winners, and Syngenta. Levente Kiss of the Plant Protection Institute of the Hungarian Academy of Science, Budapest has collaborated on the identification of powdery mildews. Master Gardener volunteers in Suffolk, Nassau and Dutchess Counties in NY received some training through viewing the results of this project. TARGET AUDIENCES: The target audience for this project includes greenhouse growers, horticultural industry salespeople and technical representatives, plant breeders, cooperative extension educators, as well as horticulturists and plant pathologists. These are all reached through extension education. Racial and ethnic minorities are represented in each of the audiences targeted. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
New knowledge was obtained through the activities funded by this project, resulting in information that is being used to train greenhouse growers in better disease management skills. Extremely low verbena powdery mildew susceptibility was identified in a number of Superbena cultivars (Dark Blue, Large Lilac Blue, Pink Shades and Purple), Lanai cultivars (Blue 08, Deep Purple, Purple Star, and Red 07) and one Aztec cultivar (Violet). Greenhouse growers will thus be able to grow these cultivars with minimal or no fungicide inputs. Growers will now know that verbenas Babylon Neon Rose and Babylon White, in contrast, will need to be scouted regularly for powdery mildew symptoms, and that repeated applications of appropriate fungicides will be essential on these susceptible cultivars in the presence of the pathogen. Not only can growers use this information to guide which cultivars they choose to grow, but also plant breeders can use this data to develop more disease-resistant plants that will be offered to the plant industry in the future. Our coleus downy mildew susceptibility studies have increased growers' confidence in previous data indicating superior control with Stature DM fungicide and poor control with a number of materials that work well against other downy mildews: only Stature DM of the materials tested protected against stunting from the downy mildew in the 2008 trial. The standard fungicide Terraguard and the newly registered fungicide Pageant may be used with confidence at 8 oz per 100 gal by growers who wish to protect gerberas against powdery mildew. According to our tests, both Insignia and Phyton 27 may be used by growers to protect poinsettias against powdery mildew if this disease is detected in their greenhouses, while a new biochemical-like fungicide (Endorse) shows similar activity but high residue. This fungicide performance information will help growers avoid pesticide applications that are ineffective or potentially harmful to the saleability of their crops.
Publications
- Daughtrey, M. 2008. Alternatives for Disease Control in the Greenhouse. Northeast Greenhouse IPM Notes, 18(4):2-3.
- Daughtrey, M. 2008. Diseases That Fool You. GrowerTalks 72:80-82,
- Daughtrey, Margery. 2008. Propagation Pathology: The Basics. The International Plant Propagators Society Combined Proceedings 2007. 57:293-295.
- Daughtrey, M. 2008. Disinfecting Diseases. Greenhouse Product News 18:58-62.
- Daughtrey, M.L., and M. Tobiasz. 2008. Comparison of verbena cultivars for susceptibility to powdery mildew, 2007. Plant Dis. Management Reports 2:OT013.
- Daughtrey, M., and M. Tobiasz. 2008. Poinsettia powdery mildew control with fungicides. Long Island Horticultural Research & Extension Center 2007 Annual Report, p. 34.
- Daughtrey, M. and M. Tobiasz. 2008. Test of phytotoxicity of some new fungicides to poinsettia. Long Island Horticultural Research & Extension Center 2007 Annual Report, p. 35.
- Daughtrey, M., and M. Tobiasz. 2008. Powdery mildew control on gerbera. Long Island Horticultural Research & Extension Center 2007 Annual Report, p. 35.
- Daughtrey, M., and M. Tobiasz. 2008. Powdery mildew control on dahlia. Long Island Horticultural Research & Extension Center 2007 Annual Report, p. 36.
- Daughtrey, M., and M. Tobiasz. 2008. Verbena powdery mildew cultivar comparisons. Long Island Horticultural Research & Extension Center 2007 Annual Report, p. 36-37.
- Daughtrey, M., and M. Tobiasz. 2008. Coleus evaluation for downy mildew susceptibility. Long Island Horticultural Research & Extension Center 2007 Annual Report, p. 37.
- Daughtrey, M., and M. Tobiasz. 2008. Evaluating lilac resistance to powdery mildew. Long Island Horticultural Research & Extension Center 2007 Annual Report, p. 55.
- Kiss, L., T. Jankovics, G.M. Kovacs, and M.L. Daughtrey. 2008. Oidium longipes, a new powdery mildew fungus on petunia in the USA: a potential threat to ornamental and vegetable solanaceous crops. Plant Dis. 92:818-825.
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Progress 10/01/06 to 09/30/07
Outputs
OUTPUTS: Powdery mildew and downy mildew diseases of importance to the greenhouse flower industry were the focus of research during 2007. Thirty-three cultivars of verbena from five different propagation companies were rated for susceptibility to the powdery mildew Podosphaera xanthii in a greenhouse trial. The percentage of foliage covered with powdery mildew was evaluated 7 times over the trial period from 28 March to 29 June, allowing identification of both highly resistant and highly susceptible cultivars. Some cultivars showed only 0-1 percent powdery mildew coverage, while others showed over 50 percent of the upper foliage surface colonized by the fungus. A coleus trial tested 49 cultivars for resistance to downy mildew caused by a species of Peronospora: all developed sporulation and were therefore clearly hosts, but most cultivars retained their foliage after outplanting to the field. Seed of 23 coleus cultivars was planted and grown under conditions suitable for downy mildew
development, but no evidence of seed transmission was obtained. Experimental and registered fungicides and biofungicides were tested for control of powdery mildew on gerbera, dahlia, and poinsettia in the greenhouse. The biological control product, Actinovate SP, applied with Latron B-1956 spreader-sticker, gave significant but insufficient control of powdery mildew on poinsettia and left no objectionable residue. Phytotoxicity and residue from new powdery mildew control materials on poinsettias Freedom Red was evaluated in a separate experiment. Many products left objectionable residue and chlorotic bract spotting was observed on Freedom Red poinsettia treated with the experimental fungicide Palladium at the rates tested. Results of these studies have been reported directly to plant propagation companies and agrichemical companies, as well as to cooperative extension educators and greenhouse growers through presentations at national and regional conferences.
PARTICIPANTS: Margery Daughtrey, P. I., oversees the project. George Hudler, P. I., supervises M. Daughtrey. Maria Tobiasz, Research Technician, conducts greenhouse and field trials under the supervision of M. Daughtrey. Partner organization: Mary K. Hausbeck, Michigan State University collaborates on research on downy mildew and powdery mildew management. Collaborators: Nora Catlin, cooperative extension educator and floriculture specialist; Bill Miller, floriculture professor; Jeff Keil, grower, Otto Keil Greenhouses; and Brian Morris, grower, Beds and Borders all provide advice as needed.
TARGET AUDIENCES: Target audiences: Greenhouse growers, cooperative extension educators, agrichemical companies, ornamental plant propagation companies, flower seed companies, horticultural supply companies, Master Gardeners, horticultural scientists and plant pathologists. Curriculum development effort: a chapter on powdery mildews was revised in 2007 for a plant pathology textbook. Other educational efforts: research results were described at the Cornell Floriculture Field Day, Ithaca, NY, the Plant Science Day at the Long Island Horticultural Research and Extension Center in Riverhead, NY, the OFA Short Course in Columbus, OH, the Ball Grower Experience in Cleveland, OH and bedding plant schools and floriculture conferences in Latham, New Paltz and Ronkonkoma, NY during 2007.
Impacts
Verbena propagation companies are utilizing the information obtained in the powdery mildew cultivar comparison trial (and in a sister trial at Michigan State University) to develop and market plants that are less prone to this common disease. The cultivars Superbena Coral, Superbena Pink Shades, Aztec Dark Red, Rapunzel Lilac and Lascar White have been identified as very highly resistant, and thus greenhouse growers will be able to produce them with minimal or no fungicide inputs. Verbenas Rapunzel Hot Rose and Empress Pink, in contrast, should be grown with a careful scouting program and readiness to use fungicides at the first indication of powdery mildew. As a result of our coleus downy mildew susceptibility studies, coleus growers are now informed of the wide-ranging vulnerability of their crop to downy mildew, and will know to grow these plants with careful attention to environmental conditions and preventive sprays to avoid spread of the disease during the spring
production season. The use of resistant cultivars to avoid downy mildew on coleus do not appear to be an option at the present time. Some coleus cultivars, such as Florida City Chuluota, showed such strong leaf curling and spotting symptoms of downy mildew in our trial that growers will be less likely to opt to grow them. Growers have been made aware of the appropriateness of the newly-registered strobilurin fungicide containing pyraclostrobin (Insignia) for control of powdery mildew fungi on dahlia and poinsettia, but have been spared ineffective applications of this same fungicide on gerbera for powdery mildew control. Applications of a new formulation of azoxystrobin (Heritage TL) have been found to be non-phytotoxic and low-residue on poinsettias. The biofungicide Actinovate SP has been shown to have utility for powdery mildew management in poinsettias, but will need to be integrated into a program with other materials to provide protection under high disease pressure. High
effectiveness against the powdery mildew of poinsettia has been shown for BAS 516 08F, BAS 516 04F and Palladium, all potential products for the ornamentals industry. BAS 516 04F and BAS 516 08F also showed excellent control of powdery mildew on dahlia, and very good control of powdery mildew on gerbera. Data on fungicide performance will be taken into account by agrichemical companies as they refine product formulations and rates for the use of the flower industry.
Publications
- Daughtrey, M., Tobiasz, M. and Komorowska-Jedrys, J. 2007. Powdery mildew control on verbena with biological and chemical fungicides. 2006 Annual Report, L. I. Horticultural Research & Extension Center, Cornell University, Riverhead, NY, p. 35.
- Daughtrey, M. L., Hodge, K. T. and Shishkoff, N. 2007. The Powdery Mildews. Chapter 14, Pages 131-141 In Trigiano, R. N., Windham, M. T. and Windham, A., eds. Plant Pathology Concepts and Lab Exercises, 2nd ed. CRC Press, 558 pp.
- Daughtrey, M. and Tobiasz, M. 2007. Host range studies on coleus downy mildew. 2006 Annual Report, L. I. Horticultural Research & Extension Center, Cornell University, Riverhead, NY, p. 33.
- Daughtrey, M. and Tobiasz, M. 2007. Downy mildew control on coleus with fungicides I. 2006 Annual Report, L. I. Horticultural Research & Extension Center, Cornell University, Riverhead, NY, pp. 33-34.
- Daughtrey, M. and Tobiasz, M. 2007. Downy mildew control on coleus with fungicides II. 2006 Annual Report, L. I. Horticultural Research & Extension Center, Cornell University, Riverhead, NY, p. 34.
- Daughtrey, M. and Tobiasz, M. 2007. Downy mildew control on coleus with fungicides III. 2006 Annual Report, L. I. Horticultural Research & Extension Center, Cornell University, Riverhead, NY, pp. 34-35.
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