Source: CORNELL UNIVERSITY submitted to
MANAGING NEW DISEASES OF ORNAMENTALS
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
NEW
Funding Source
Reporting Frequency
Annual
Accession No.
0231325
Grant No.
(N/A)
Project No.
NYC-153452
Proposal No.
(N/A)
Multistate No.
(N/A)
Program Code
(N/A)
Project Start Date
Oct 1, 2012
Project End Date
Sep 30, 2015
Grant Year
(N/A)
Project Director
Daughtrey, MA.
Recipient Organization
CORNELL UNIVERSITY
(N/A)
ITHACA,NY 14853
Performing Department
Plant Pathology
Non Technical Summary
This proposal addresses a pressing need for information on several alarming new ornamental diseases looming over important crops: one that destroys impatiens, a top bedding plant; one that threatens chrysanthemum, a widely-grown staple of the flower industry; and one that has the potential to convert a popular problem-free flowering street tree into a high-maintenance ornamental that will require fungicide applications in order to perform well in the landscape. By initiating research on the downy mildew affecting impatiens and the rust fungus diseases of chrysanthemum and callery pear, solutions can be worked out and shared that will help to preserve the profitability of these crops for the greenhouse growers and nurserymen who count on them as moneymakers. Environmentally safe and sustainable solutions are especially desirable for the control of ornamental plant disease problems. Public funding support is important because of the minor crop status of these ornamentals, which are nevertheless critical to the livelihoods of men and women in small to large agribusinesses across New York and the rest of the United States. It is hoped that the approaches that will be used in this research will identify sustainable solutions to these rising disease problems, allowing preservation of environmental quality in community, corporate and home plantings of ornamentals. In these experiments, impatiens, chrysanthemums, and pears will be compared for their susceptibility to these new diseases, or treated with different cultural, chemical or biological control measures to see if the problems can be mitigated. The treatments will be replicated to allow statistical analysis of the data that is collected over the years of the project. Growers and the gardening public will be constantly kept informed of the progress of the research through presentations and articles in trade journals.
Animal Health Component
(N/A)
Research Effort Categories
Basic
(N/A)
Applied
(N/A)
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
2122110116033%
2122123116057%
2152123116010%
Goals / Objectives
The objectives of this study are spread across three important host-pathogen systems that are new disease management challenges for producers of ornamental plants in recent years. For Downy Mildew of Impatiens: A1) to learn about the susceptibility of plants at different ages A2) to learn the effect of systemic and contact fungicides and biological controls as protectants and A3) to compare a wide range of impatiens germplasm for susceptibility to the disease. For Chrysanthemum Brown Rust: B1) to learn how the pathogen is surviving from year to year and B2) to develop a spray program using the most environmentally-safe fungicides that will curtail disease development. For Pear Trellis Rust on Callery Pear: C1) to survey nurseries to determine the relative susceptibility of Bradford pear and newer cultivars C2) to compare common junipers grown in nurseries for their ability to host the rust fungus and C3) to collect callery pears not yet commonly grown and trial them for their susceptibility to the disease. Each of the disease problems being studied is new and unfamiliar, yet clearly threatening to the profitability of nurserymen and greenhouse growers. The intended outcome of all of these studies is to collect information that propagation companies, growers, arborists or landscapers can use to manage these problems effectively, preserving ornamental crop profitability and landscape beauty with no harmful effects on the environment, through skillful application of integrated pest management practices. For the three diseases, there should be improved knowledge of which plants to grow to avoid disease, which times are critical for control actions, and which plant protection materials are helpful. Scientific knowledge of the impatiens downy mildew will be particularly valuable, as this disease has received very little study since its world debut in 2003. Similarly, brown rust of mums is now causing losses for growers in NY state. Pear trellis rust has recently appeared on the east coast, and is causing serious injury to ornamental pears. These studies will contribute to the goal of developing economically and environmentally sound practices for the production and landscape use of three key ornamental species, helping horticultural businesses to maintain their profitability by making wise choices of which cultivars to grow and which treatments to choose. By December 2012, we will have surveyed nurseries to learn which currently grown cultivars of callery pear are susceptible to pear trellis rust. By June 2013, we will identify the effect of impatiens plant maturity on downy mildew susceptibility. By Dec 2014, we will have identified protective fungicides and biocontrols for impatiens downy mildew and for brown rust of chrysanthemums. By July 2015, we will know the effect of winter gardening practices on brown rust of chrysanthemum, which species of locally-grown junipers are alternate hosts for pear trellis rust, and will hopefully have identified some callery pear cultivars less at-risk from pear trellis rust. By September 2015, we will have useful data on ornamental impatiens' susceptibility to downy mildew.
Project Methods
All data will be replicated and statistically analyzed to determine significant differences. A1. For downy mildew of impatiens, inoculations will be made using sporangia washed from infected leaves to infect plants of I. walleriana cv. Xpress Red at four stages: cotyledon, first true leaf expanded, and one and two months later. Plants will be seeded at different times so that the different stages of growth will be available simultaneously. Infection will be tried on both upper and lower leaf surfaces, growing plants in a plastic chamber in the greenhouse fitted with a room humidifier. Percent of leaves with sporulation will be recorded 10 days post-inoculation. This data will be used to guide growers on when to protect their plants and on the importance of lower leaf surface coverage. A2. Systemics (the fungicides mefenoxam, dimethomorph, fluopicolide, and azoxystrobin), contacts (copper, mancozeb, and bicarbonate), and biologicals (Bacillus subtilis and Streptomyces griseoviridis) will be applied prior to plant inoculation to compare their protective ability. A3. Twelve Impatiens cultivars and species (including the two species native to the Northeast) will be compared for susceptibility to downy mildew supplied from a natural source of inoculum, and this information will be shared with plant breeders. B1. For chrysanthemum brown rust, beds of a highly susceptible cultivar (Brunette Barbie or Hankie Yellow) will be established and either left alone, cut back and mulched, or cut back to ground level in the fall, so that early disease development can be assessed each spring, comparing the three gardening systems for their effect on disease. B2. Spray programs using biological, non-restricted-use and reduced-risk materials for rust control will be compared on container-grown plants of Brunette Barbie. C1. For pear trellis rust, 3 local nurseries will be surveyed for incidence and severity of pear trellis rust symptoms on a wide range of pear cultivars in September. C2. Junipers of 12 cultivars representing the species listed as hosts will be propagated and exposed to natural rust inoculum in nurseries in fall and will be examined for galls the following spring to compare their susceptibility. C3. Different cultivars of callery pear will be exposed to inoculum on junipers in May so that their susceptibility can be assessed under one set of environmental conditions using one source of inoculum. Disease incidence and severity will be recorded. Findings will be disseminated to growers at extension meetings and in industry trade journals, and published in scientific journals. Ten NY floriculture businesses will be surveyed in 2012 and 2014 to determine changes in disease management for impatiens and mums. Ten NY nurseries will be surveyed for the pear and juniper cultivars they carry in 2012 and 2017, to assess changes based on knowledge of pear trellis rust disease.

Progress 10/01/12 to 09/30/13

Outputs
Target Audience: Greenhouse growers, nurserymen, agrichemical tradespeople, garden center retailers, arborists, other scientists, cooperative extension educators, home gardeners, Master Gardeners, landscape gardeners. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest? To increase public understanding, a presentation was given at the Chappaqua Library in Chappaqua, NY to 150 people on Global Gardening, describing invasive disease challenges and our research on them on 18 April 13, and a presentation on Outwitting Diseases was presented at the Long Island Gardening Symposium to 60 home gardeners on 21 Sept 2013 in Bridgehampton, NY. Presentations to the most concerned communities of interest which covered research in this project included: to 150 arborists, landscape gardeners and nurserymen at the Westchester Tree Conference in Yonkers, NY, Life After Impatiens Downy Mildew and Boxwood Blight, on 8 Jan 2013; to 60 landscape gardeners and nurserymen at the Long Island Horticulture Conference in Ronkonkoma, NY, Impatiens Downy Mildew, the Morning After on 25 Jan 2013; to 55 arborists at the NY State Arborists Association meeting in Suffern, NY, Cornell Update, Box Blight and Other Diseases, on 27 Jan 2013; to 45 greenhouse and nursery growers and garden center operators in Middletown, NY at the Hudson Valley Nursery and Greenhouse School, Disease Identification and Control on Greenhouse and Nursery Crops, on 30 Jan 2013; to 60 landscape gardeners at the Brooklyn Landscape Gardeners Conference, Battling Blight and Mildew on Boxwood and Impatiens, on 4 March 2013; to 50 Master Gardeners at a training session at Bayard Cutting Arboretum, Great River, NY, Diseases of Ornamental Plants, on 13 Mar 2013; to 35 other scientists (professors and graduate students) in a seminar on invasive diseases of ornamentals at Oklahoma State University, Knotty Disease Problems Currently Challenging Ornamental Plants, 15 April 2013; to 55 nursery and greenhouse growers in San Marcos, CA, Boxwood Blight and Other Disease Challenges, on 6 May 2013; for 40 arborists, a research tour at the Long Island Horticultural Research and Extension Center, Riverhead, NY on 14 May 2013; for 30 members of the Southampton Garden Club, Rusty, Sandy and Downy Blights and Blasts to Challenge Your Garden, on 14 June 2013; for 30 greenhouse growers, nurserymen, landscapers and arborists, a research tour at the Long Island Horticultural Research and Extension Center Plant Science Day on 11 July 2013; for 125 greenhouse growers, agrichemical industry representatives, and garden center operators, a talk presented with Colleen Warfield of Ball Horticultural Company on Impatiens Downy Mildew: Are We Any Closer to Control? at the OFA Short Course in Columbus OH on 13 July 2013; and a presentation to 35 scientists at the 10th Annual International Congress of Plant Pathology in Beijing, China on Newly Important Powdery Mildews and Rusts on Herbaceous and Woody Ornamentals on 30 Aug 13. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? New diseases are an additional, frustrating challenge for growers of flower and nursery crops, landscape designers and maintenance firms, on top of the problems posed by the all-too-familiar diseases. Increased globalization has increased the frequency of introduction of organisms that can cause diseases on ornamental plants. In recent years, new or re-emerging diseases have arisen to threaten chrysanthemum, callery pear and impatiens bedding plants: two rusts and a downy mildew. These lead to increased cost of production and maintenance because of the cost of plant protection, and reduced customer satisfaction. This research study aims to alleviate these new diseases by improving our knowledge base, helping the green industry to make better-informed decisions that reduce the need for control actions. In this way, the least expensive, most effective, and most environmentally responsible options may be employed as floral and nursery crop businesses seek to improve the quality of the living environment with ornamental plants. At the Long Island Horticultural Research and Extension Center of Cornell University, we have inititated studies to address challenges posed by a new rust fungus disease on chrysanthemum that causes ugly leaf spotting during flowering, a rust of the callery pear that recently appeared on the east coast of the United States that also disfigures foliage, and a downy mildew of impatiens that defoliates and dramatically kills plants in the landscape. Impatiens make up as much of 70% of the spring crop for bedding plant growers in the Northeastern U.S., so helping plant breeders to find long term solutions and helping growers and landscapers to cope in the short term are important to profitability of most bedding plant businesses. Our studies include nursery surveys and chemical control trials to collect information that will expand management options for these new diseases. A1) Research continues A2) A study showed copper sprays (Phyton 35 and Phyton 27) applied at 30 fl oz per 100 gal to be ineffective against impatiens downy mildew with weekly application in a field trial started 13 Sept in which 79-82 percent of the foliage of nontreated controls and copper treated plants showed sporulation on 10 Oct; impatiens sprayed with SubueMAXX at 1 fl oz per 100 gal, however, were larger than those in other treatments and showed no downy mildew sporulation on 10 Oct. In another trial, soil incorporation of mefenoxam (Subdue G) at 30 oz per 1000 sq feet completely protected field grown impatiens against downy mildew from the time of outplanting on 12 Sept to final rating on 10 Oct: 91% of nontreated control plants showed sporulation but there was no sporulation on the plants in Subdue G treatments. In a season-long trial, an experimental phosphorous acid A14658C at 20 fl oz per 100 gal and mefenoxam (SubdueMAXX) at 1 fl oz per 100 gal used separately or in combination gave prolonged protection against impatiens downy mildew when applied as a drench at 1 pint per sq ft on 28 June. Top quality ratings were still high (4.3 - 5 on a 5 point scale) on August 13 for plants drenched once with A14658C or mefenoxam the day of outplanting and exposure to inoculum. In a study in which impatiens were exposed to inoculum on 26 Sept, two 14-day interval protective treatments with a dimethomorph plus amectotradin fungicide (Orvego) at 14 fl oz per 100 gal resulted in complete suppression of sporulation of downy mildew at 11 days after the 2nd treatment. There was still strong suppression from Orvego treatment 20 days after the second treatment (less than 1 leaf with sporulation per plant) compared to over 10 sporulating leaves per plant in nontreated controls. Their remains a need to identify materials which are both effective and labeled in such a way that they could be used for practical disease management in the landscape, where the likelihood of fungicide resistance development is especially high because of the paucity of chemical options. Our promising results with mefenoxam, phosphorous acid, strobilurin and dimethomorph active ingredients potentially represent four different mode of action groups that could be brought into play against impatiens downy mildew. A3) Impatiens walleriana, I. hochstetteri, I. balsamina, I. flanaganiae, I. capensis, I. auricoma and I. arguta all showed some susceptibility to Plasmopara obducens, the impatiens downy mildew, as evidenced by sporulation on plants exposed to inoculum in a replicated trial in an outdoor shade house with overhead irrigation. Impatiens that did not develop symptoms or sporulation of downy mildew under these same conditions were I. hawkeri (New Guinea impatiens), an interspecific hybrid SunPatiens 'Deep Rose', I. balfouri, I. 'Blue Angel', I. namchabarwensis, I. omeiana, I. glandulifera, I. morsei and I. tricolor, Although only the New Guinea impatiens and its hybrid have the form and cultural characteristics to be a direct alternative to I. walleriana, the other species may serve as a source of resistant germplasm for plant breeders. B1) Studies are ongoing. B2) Chrysanthemum brown rust was studied, looking at fungicide application methods and timing for optimum disease management. The reduced-risk fungicide Heritage 50WDG at 1.13 g per gal plus Capsil at 1 ml per gal performed very well as a spray at a 14-day interval against Puccinia chrysanthemi brown rust. There were major differences seen in susceptibility of the three cultivars tested: for nontreated plants of cv. Golden Cheryl, 29 leaves per plant were infected, whereas for Brunette Barbie only 12 leaves per plant were infected and Hankie Yellow developed no rust symptoms. Avoiding a highly susceptible cultivar such as Golden Cheryl will help a grower to have an effective disease management program. C1) Two nurseries were surveyed in 2013 to observe symptoms of pear trellis rust on different callery pear cultivars, and samples were collected for molecular identification. The cultivar Capital appeared to have less severe symptoms (smaller lesion size) than Cleveland Select and others known to be very susceptible; future studies will attempt to verify this observation and consider additional cultivars. Rather than developing chemical controls for this disease of a widely planted ornamental street tree, it seems most appropriate to identify trees with the desirable flowering traits but reduced symptoms from infection with pear trellis rust. C2) Research is ongoing. C3) Research is ongoing.

Publications

  • Type: Other Status: Published Year Published: 2013 Citation: Daughtrey, M. and Hyatt, L. 2013. Downy mildew overwintering trial. 2012 Annual Research Report, Cornell University Long Island Horticultural Research and Extension Center. Page 39.
  • Type: Other Status: Published Year Published: 2013 Citation: Daughtrey, M. and Hyatt, L. 2013. Testing copper treatments for protection of impatiens against downy mildew. 2012 Annual Research Report, Cornell University Long Island Horticultural Research and Extension Center. Pages 38-39.
  • Type: Other Status: Published Year Published: 2013 Citation: Daughtrey, M. and Hyatt, L. 2013. Downy mildew management with granular fungicides. 2012 Annual Research Report, Cornell University Long Island Horticultural Research and Extension Center. Page 37-38.
  • Type: Other Status: Published Year Published: 2013 Citation: Daughtrey, M. and Hyatt, L. 2013. Downy mildew management with fungicide drenches. 2012 Annual Research Report, Cornell University Long Island Horticultural Research and Extension Center. Page 36-37.
  • Type: Other Status: Published Year Published: 2013 Citation: Catlin, N., Daughtrey, M., Hyatt, L., and Jedrys, J. 2013. Impatiens susceptiblity to downy mildew caused by Plasmopara obducens. 2012 Annual Research Report, Cornell University Long Island Horticultural Research and Extension Center. Page 35-36.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Daughtrey, M.L. and Kiss, L. 2013. Newly important powdery mildews and rusts on herbaceous and woody ornamentals. Proceedings, 10th International Congress of Plant Pathology, Beijing, China. Acta Phytopathologica Sinica (suppl.) 43:184