Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 3/31/2001
Publication Date: 6/30/2001
Citation: PFENDER, W.F. PREDICTION OF STEM RUST INFECTION SEVERITY IN PERENNIAL RYEGRASS, BASED ON OVERNIGHT AND POST-SUNRISE DEGREE-HOURS OF MOISTURE DURATION. PHYTOPATHOLOGY. 2001. v. 91. p. S72.
Technical Abstract: Infection of perennial ryegrass (Lolium perenne) by Puccinia graminis subsp. graminicola occurs during the night and early morning. To determine the relationship between weather conditions and infection severity, plants were inoculated with a standardized urediniospore suspension and placed outdoors overnight; temperature and leaf wetness were recorded at 30-minute intervals. The experiment was conducted weekly from March-July in 1998 and 1999. From these data, we developed a model based on the physiological time (degree-hours above 1.5 C) during which leaves were wet. The model is a form of the Hill equation. It uses wetness degree-hours during the 150 min. after sunrise, and the square root of night time (dark) wetness degree hours, to predict the logarithm of number of infections per standard leaf area. Data for two additional seasons, Sept.-November 1999 and March-July 2000, were used to evaluate the model.