2009 Annual Report 1a.Objectives (from AD-416) Quantify the occurrence and distribution of emerging pathogens, especially choke and smut fungi, that impact the production and export of turf and forage seeds; characterize environmental and biological factors that affect the epidemiology of the economically important grass pathogens Epichloe and Puccinia; identify host characteristics that impact resistance of grasses to ergot; develop and add an overwinter survival component to a stem rust prediction model; and implement a web-based disease management decision tool for stem rust in grasses. 1b.Approach (from AD-416) Distribution and occurrence of emerging pathogens are quantified through disease surveys. Environmental factors that affect development of Epichloe and Puccinia or affect resistance to ergot are elucidated under controlled environment or field conditions. Statistical, epidemiological, and systems analysis techniques are used to develop and integrate disease prediction subcomponents into a comprehensive stem rust prediction model used in a web-based decision aid for optimization of timing of fungicides for stem rust control. Formerly 5358-22000-031-00D (3/07). 3.Progress Report Choke is a newly emerged disease that causes significant (up to 30%) seed yield losses. Studies of the effects of environmental conditions on spore survival in the fungal pathogen that causes choke in orchardgrass were completed. In addition, in collaboration with others, the timing of release and concentration of spores of the choke pathogen was determined. Results indicate that under field conditions, spore availability for infection extends later in the season than expected. Newly discovered and emerging smut diseases of grasses and grass seeds are of particular concern in terms of the production and export of seeds. Surveys of smut fungi in grass seed are in progress. A database, based on OSU Seed Lab and Seed Certification data, was created for years 2002-2004. This provides historical data on the host and geographical occurrence of grass seed pathogens and weed seed contaminates in grass seed. The database is facilitating and augmenting smut diseases surveys of grasses. Ergot is an important disease of Kentucky bluegrass that reduces seed yields. In collaboration with others, the timing of release and airborne concentration of spores of a grass infecting fungus, referred to as ergot, was determined. Results indicate the potential for predictive modeling of spore release to better time and reduce fungicide applications for ergot control. A naturally occurring potential biocontrol agent for the fungal grass pathogen that causes choke disease in orchardgrass was discovered. In greenhouse and field plot studies, application of the fungus significantly reduced the development of choke. Thrips that infest grass seed have recently been found in grass seed production fields in the Pacific Northwest. In collaboration with others, in a survey of thrips in grasses, seed infesting thrips were found to be not only widespread but have the potential for spread with seed Stem rust is a potentially devastating disease of perennial ryegrass. A study was conducted on 5 ryegrass cultivars to quantify host attributes that impact the development and spread of rust. Host susceptibility, rates of plant growth, and rust survival potential among the cultivars were determined and related to environmental conditions. 4.Accomplishments 1. Quantifying economic impact of stem rust disease in grass seed production. Stem rust is the most damaging disease affecting the production of cool- season grass seed crops. U.S. growers spend millions of dollars each year to mitigate its damage. ARS scientists in Corvallis, OR used data from 9 years of field experiments to derive a simple equation relating severity of rust disease to loss in seed yield. This result will allow farmers to make appropriate economic decisions about the relative costs of management vs yield reduction for this critical production problem. 6.Technology Transfer Number of Web Sites Managed 1 Review Publications Pfender, W.F., Eynard, J. 2009. Field assessment of a model for fungicide effects on within-plant spread of stem rust in perennial ryegrass seed crops. Phytopathology. 99:696-703. Pfender, W.F. 2009. A Damage Function for Stem Rust of Perennial Ryegrass Seed Crops. Phytopathology. 99:498-505.