Investigations on the distribution and yield losses caused by the sugar-beet powdery mildew (Erysiphe betae) in Germany, Austria and Turkey

Sugar-beet powdery mildew, Erysiphe betae (Van.) Weltzien, the most important leaf disease in summer dry sugar-beet production, can also build up an epidemic in the Central European sugar-beet growing areas, if an early disease development in Central Anatolia and in the Pannonic region precedes. However yield losses remain minimal because of the pathogen’s late arrival. Several plot experiments conducted in the Rhine area (West- Germany), in Pannonia (East-Austria) and in Central Anatolia (Turkey) from 1976 to 1979 were analyzed to study the relationships between the date and intensity of infection with powdery mildew and losses in sugar yield. Cercobin M + wettable sulphur were used for differentiating the infection. Artificial inoculation took place in monthly intervals beginning with early June. With the time (x) between infection and harvest (in months), infestation/crop loss relationships were established, which may be approximately described with the functional equations 9 1). m is a Ypot Ypot (e n’ o – parameter for the severity of disease development and is derived from weather and infection data. Some sugar-beet varieties were tested for their susceptibility or resistance. The interactions between the degree of susceptibility and the extent of crop losses under varying infection conditions used to describe the reaction of various cultivars on Erysiphe infection.