Use of powdery mildew (Blumeria graminis f. sp tritici) resistance in winter wheat varieties in integrated protection models

Incidence of powdery mildew (Blumeria graminis f. sp. tritici) in sets of 2 0 and 15 winter wheat varieties was studied in experiments conducted in 199 5 to 1999. Based on data obtained in individual evaluations, an average inf ection of each variety was assessed and the data were used to calculate the area under disease progress curve (AUDPC). Since the infection of upper le af layers is critical for yield formation, leaf infection was evaluated in the period between the jointing stage (DC 39) and anthesis (DC 69) and desi gnated AUDPC-part. Significant differences in the infection of individual v arieties were found in all examined years. The highest infection was found in the Varieties Regina and Bruneta. By contrast, Estica and Zdar exhibited the lowest infection. There was no significant difference in powdery milde w incidence in 1995 to 1997. On the contrary, significant differences were assessed in the years from 1997 to 1999. The highest powdery mildew inciden ce was observed in 1999. Experiments with fungicide application were carrie d out for both highly susceptible varieties (Regina and Bruneta) aiming at suppression of powdery mildew and consequently other leaf diseases (leaf ru st and Septoria glume blotch). Fungicides were repeatedly applied when a fu ll (registered) fungicide dose was used in the first treatment and a lower dose in the second one. Both a good state of health and high yield increase were obtained. The model shows that varieties highly susceptible to powder y mildew and then to other leaf diseases are necessary to be treated repeat edly, however, the application does not require full (registered) fungicide doses even in years with a high infection pressure of leaf diseases. Detai led results are given for 1999 when the highest occurrence of both powdery mildew and the other leaf diseases was observed.