Plant Pathology
Contact
Jane Stewart
Associate Professor – Plant Pathology
Department of Agricultural Biology
College of Agricultural Sciences
jane.stewart@colostate.edu
Plant Pathology Research Questions and Answers
Are canopy sprays an effective management tool for Cytospora canker?
Canopy sprays are typically used in Colorado to limit foliar and fruit pathogens, like Coryneum blight and powdery mildew, however, their efficacy in canker pathogens has not been well explored in fruit crops. Cytospora canker, caused by the fungal pathogen Cytospora plurivora, is the most damaging disease to peaches in Colorado. We have also detected Cytospora canker in cherry and apple, although the impact is typically less severe. We build on previous research that examined targeted sprays of pruning wounds to reduce Cytospora canker incidence. Canopy sprays, rather than targeted sprays, are more cost and time effective, which is vitally important to growers especially as the cost of labor has increased. The aim of this work is to determine if canopy sprays are effective against Cytospora canker and other fungal diseases in peach, cherry, and apple. This work is funded by the NIFA Specialty Block Crop Grant Program.
Are other fruit crops a green bridge for harboring Cytospora peach pathogens, and what is the species diversity of Cytospora within Colorado fruit orchards?
Several Cytospora spp. are documented to cause disease on peach, apple and cherry, yet management for Cytospora canker occurs mainly in peach. The importance of host specificity and the role apple and cherry orchards play in the epidemiological cycle has not been demonstrated. The goals of this research are to: 1. Survey peach, cherry, and apple orchards in Colorado to estimate Cytospora spp. incidence and severity, 2. Delineate Cytospora species distribution in fruit orchards with molecular and morphological techniques and elucidate movement within and among fruit orchards, 3. Perform pathogenicity assays to determine fruit crop host range of each Cytospora species. This work is funded by the NIFA CARE program.
What are the methods of dissemination of Cytospora spores?
We are investigating how Cytospora spores move or disseminate through the orchard using several different trapping techniques and molecular detection approaches. We are also investing sporulation rates throughout the year and pathogen virulence over a 12-month period and how this is tied to environmental conditions. Water dissemination, through irrigation systems, has been documented as the primary dispersal mechanism of Cyotspora species; few studies have reported evidence of non-water borne release of conidia spores. We are testing whether spores move through irrigation (microsprinker vs. drip), insects, and through air and testing nursery stock using a newly developed digital droplet PCR tool for Cytospora plurivora, the main peach pathogen in Colorado. The study will improve integrated pest management programs for stone-fruit growers by providing epidemiological data for targeted management practices. The work is funded by the NIFA Specialty Block Crop Grant Program, the Farm Bill, and Mesa County Pest District.