Blast Disease continued from page 1      causes blast disease on rice around the world and on St. Augustinegrass in the southern U.S. Greenhouse testing shows that other kinds of turf, such as annual and Kentucky bluegrass and creeping bentgrass, are also susceptible to the disease, but it has not been diagnosed in the field on these grasses. Uddin's studies show that the symptoms develop much more slowly on these grasses than on perennial ryegrass. He speculates that because of the slow rate of disease development and frequent mowing, the fungus may not have a chance to cause noticeable damage on these species and may not produce enough spores, or reproductive bodies, to reinfect the plants. Therefore, the disease cycle is disrupted.      Blast disease first occurs as small water-soaked lesions on the grass blades in warm humid weather. The spots expand rapidly into grayish or brownish circular spots with darker borders often surrounded by a yellow ring. The spots soon become irregularly shaped and the affected blades may appear twisted. Tip or complete blighting can occur and the entire plant is usually killed within 48 hours. Complete loss of turf can occur within three to five days.      "I'm working on predicting when the disease epidemic will occur," says Dr. Wakar Uddin checks for signs of turf disease. Courtesy W. Uddin

Uddin, "so that superintendents can use fungicide efficiently. If they know when outbreaks are most likely, they can reduce the amount of spray used and target the timing of the application." Uddin estimates that preventive fungicide applications might cost $2000 to $3000 for all the fairways of a typical golf course in Pennsylvania, rather than over $10,000 for post-infection spraying. Effective management of fungicides also benefits the environment. By targeting the fungicide application during the easiest time to kill the fungus, less of it may be needed.      Uddin wants to know more about how blast disease spreads, under what conditions it develops and reproduces, conducive soil fertility levels, which fungicides control it most efficiently, and the overwintering success of the fungus. This summer, his research crew and collaborating course superintendents are tracking site-specific weather data at turf test plots to expand the knowledge base on which a predictive model will be built.      Uddin's field, greenhouse, and lab research has shown that blast disease develops on ryegrass fairways during warm humid days and cool nights of late summer when daytime temperatures range between 75F and 90F. These conditions promote maximum leaf wetness. The leaf must remain wet for about four hours for fungal infection to take hold. Outbreaks tend to occur during periods of heavy cloud cover.      Conversely, Uddin has shown that the fungus reproduces when the air is warm and humid and the leaf is dry. So the fungus may develop in the morning and spead in the afternoon. A single infected blade of grass produces millions of spores, which are easily transported by wind, rain splashes, and on the wheels of golf carts.

This area has been devastated by blast disease. Courtesy W. Uddin Uddin suspects that spores may be transported on golfer's shoes and clubs from course to course. Rough areas along the edges of fairways can also harbor and spread the fungus.      Uddin's research indicates that some fungicides are effective in stopping the spread of blast disease, but the results have been somewhat inconsistent in some test locations. Uddin is continuing studies on fungicide efficacy to identify more reliable compounds under various turfgrass management practices. There may also be natural biocontrols for the fungus. "We have isolated a type of bacteria from the soil that has very strong inhibitory effects on this pathogen," says Uddin. "By integrating this bacteria as continued on page 6 Focus on Research is published by the Department of Agronomy, The Pennsylvania State University, University Park, PA 16802, (814) 865-6541 Editorial comments and opinions expressed in Focus on Research do not necessarily reflect the views of The Pennsylvania State University or the agronomy department. Use of trade names implies no endorsement by Penn State. DEPARTMENT HEAD: Steven L. Fales EDITOR: Joy R. Drohan This publication is available in alternative media on request. The Pennsylvania State University is committed to the policy that all persons shall have equal access to programs, facilities, admission, and employment without regard to ability, performance, or qualifications as determined by University policy or by state or federal authorities. The Pennsylvania State University does not discriminate against any person because of age, ancestry, color, disability, or handicap, national origin, race, religous creed, sex, sexual orientation, or veteran status. Direct all inquiries regarding the nondiscrimination policy to the Affirmative Action Director, The Pennsylvania State University, 201 Willard Building, University Park, PA 16802-2801; Tel. (814) 865-4700/V;(814) 863-1150/TTY.