determination of spraying turns by tridimorph fungicides for controlling of powdery mildew disease in sugar beat

powdery mildew disease caused quality and quantity losses of sugar beet production. therefore, five spraying treatments and three sugar beet variety were conducted in split plot design with four reapplications during consecutive two years in kermanshah and mashhad regions. in order to control of disease, tridimorph fungicide was used. spraying treatments were in main plot and variety in the sub plot. combine analysis showed that severity index less in sprayed treatments. with increasing number of spraying, severity index (si) was decreased. four times spraying had less si (22.42 %). treatment without spraying had the highest level of si (43.39 %). treatment with four times spraying had the highest root yield by about 69.3 t ha-1. one time spraying caused increase 2.8 t ha-1 root yield. four times spraying than control treatment (without spraying) had 5.8 t ha-1. sugar content was not affected by spraying with fungicide.