Primary infection and epidemic development of the cherry leaf spot diseaseBlumeriella jaapii (Rehm) von Arx

The leaf spot disease is a serious cherry disease. Crop quantity and qualit y can be severely diminished due to defoliation. Primary infection is caused by ascospores, produced in asci of the foilage from the previous year. There is a correlation between the number of emitted ascospores and rainfal l. As the pathogen needs distinct temperatures for a successful leaf infect ion, this process does not take place at the moment of maximum emission of ascospores, but much later. The epidemic spread of the disease in the orchard also depends on the weath er conditions.