Transmission of Stagonospora nodorum and Fusarium spp. on Triticale and Wheat Seed and the Effect of Seedborne Stagonospora nodorum on Disease Severity under Field Conditions

Spring and winter triticale and wheat were used to study seed transmission and the effect of seedborne inoculum on Stagonospora nodorum blotch in the field. Infected seed was shown to serve as a source of primary inoculum in epidemics of the disease in cereals. Seedborne Stagonospora nodorum (Berk.) was detected efficiently on oxgall agar medium as well as on yeast malt extract and potato dextrose agar media. The effect of seed infection with S. nodorum on subsequent leaf and glume blotch severity in the field was studied in triticale and wheat as well as the effect on seed infection of fungicides normally used in disease management programtnes. Planting of highly infested seed resulted in more severe Stagonospora nodorum blotch than did the planting of healthy or only slightly infected seed. However, environmental conditions contributed considerably to disease severity. Correlation of level of seed infestation and subsequent disease severity in individual varieties was low and it was only statistically significant for spring triticale. Seed of triticale and wheat from plants treated with foliar fungicides was infested with S. nodorum significantly less than seed from untreated plants. The fungicides recommended for Stagonospora nodorum blotch control in cereals did not prevent, and even enhanced, seed infestation by Fusarium spp