Epidemiologische Untersuchungen zur Ascosporenfreisetzung von Pseudopezicula tracheiphila (Mull.-Thurg.) Korf and Zhuang, dem Erreger des Roten Brenners am Wein

In the last years, the rotbrenner, a foliar disease on grape, is steadily increasing in European vineyards. The development of a forecasting system for an integrated control of rotbrenner requires a thorough knowledge of the epidemiology of Pseudopezicula tracheiphila. Investigations on the ascospore discharge in Pseudopezicula tracheiphila showed that the induction of apothecia does not depend on cool periods. Rainfall and larger periods of wetness favored the development and the maturation of apothecia on overwintered leaves and caused the maturation of ascospores. The quantity of rainfall which is needed to release the ascospores depends on the wetness of the leaves containing apothecia. Infections in later summer are caused by late development of apothecia on the overwintered infected leaves as well as by apothecia formed on infected and fallen leaves from the same year. The release of ascospores is not influenced by daylight. It always occurs after and sometimes during rainfall events. The quantity as well as the severity of rainfall influence ascospore discharge whereas temperature does not seem to play an important role. Graduated application of fungicides showed that the vine is susceptible after the fifth leave is unfolded. Losses in yield are possible if early infections result in severed defoliation during blossom-time. Application of fungicides are recommended after a rainfall event when ES 15 is reached. The following treatment depends on plant growth and another rainfall period. Locosystemic and systemic fungicides allows treatments until 2 days after a rain event. After bloom, the control can be combined with sprays against downy mildew Plasmopara viticola. It is further known that at this stage of plant growth high levels of infection are not possible and that the vine plant is able to compensate defoliation.