EFFECT OF CULTIVAR ON THE EFFICIENCY OF FUNGICIDES IN CONTROLLING POWDERY MILDEW OF FLAX AND RELATIONSHIP OF AGRONOMIC AND TECHNOLOGICAL TRAITS TO DISEASE SEVERITY

A two-year field study was conducted at El-Ismailiya, Egypt, to evaluate the fungicides Bellis and Sulphurs applied as a foliar sprays for controlling powdery mildew on six flax cultivars. Disease severity, straw yield, and seed yield were used as criteria for evaluating the performance of fungicide on the tested cultivars. Analysis of variance (ANOVA) showed that each of the fungicides and cultivar was highly significant source of variation (p = 0.000), in disease severity, strae yield, and seed yieled. ANOVA also showed that fungicide x cultivars interaction was a highly significant source of variation (p = 0.000) in disease severity, while it was insignificant in straw and seed yields. Both fungicides were effective in reducing disease severity; however, sulphur surpassed Bellis in increasing straw yield and seed yield. Therefore, linear regression analysis was used to determine the relationship between agronomic or technological traits and powdery mildew severity (PMS). All traits showed significant negative correlations with PMS after the appliction of fungicides, which suggest that control of late-season powdery mildew could be economically important when PMS on flax cultivars is high.