BIOLOGICAL PROPERTIES AND FIELD PERFORMANCE OF FUNGICIDES FOR CONTROL OF WINTER BARLEY FOLIAR DISEASES

Fungicides with different modes of action against barley disease were applied singly and as mixtures to two winter barley cultivars ('Igri' and Sonja') that differed in susceptibility to the principal pathogens. Observations were made of the effects of the fungicides on inoculum production of Erysiphe graminis and Rhynchosporium secalis, on infection, and the persistence of these fungicidal effects were measured. Inoculum suppression, produced to different degrees by most of the fungicides, was reflected in disease development. Triazole fungicides applied in the spring (GS 31) suppressed mildew development for 21 days; adding a morpholine extended this to at least 31 days. Treatments that contained an imidazole prevented the development of new net blotch and leaf blotch lesions for 34 and 38 days, respectively. Other mixtures were less effective and cultivar dependent. All spring fungicide treatments (applied at GS 31 + GS 39) controlled disease and increased yield, the most effective being flusilazole + carbendazim. November-applied fungicides decreased spore production of powdery mildew and disease during autumn and spring but had no effect on yield when followed by two spring sprays.