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
Research Effort Categories
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.
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.