The relationship of leaf wetness duration and disease progress of glume blotch, caused by Stagonospora nodorum, in winter wheat to standard weather data

Almost 50% of the variation in leaf wetness duration can be explained by maximum and minimum temperatures, rainfall and hours with relative humidity above 90% on a daily basis. All of these parameters can be estimated from a standard weather station. If variables related to wind are added the level of explanation increases to 69-76%. Leaf wetness duration explained up to 42% of the rate of disease increase (RDI) for S. nodorum. Leaf wetness duration was accumulated over a 5-day 'window' period and correlated with rate of disease increase after a 7-day 'lag' period. Standard weather variables could explain 20-34% of the disease increase. The relevance of these statistical models to disease prediction is discussed.