Fusarium seedling blight of wheat and oats: effects of infection level and fungicide seed treatments on agronomic characters

The effects of seed-borne Fusarium spp. and Microdochium nivale infection in spring wheat, winter wheat, and oats in Sweden was investigated in field trials for the agronomic characters yield, thousand kernel weight, grain volume weight, gluten, protein, starch, straw strength, and plant density. Seed with high and low levels of infection was mixed to obtain six infection levels in the proportions of 100/0, 80/20, 60/40, 40/60, 20/80, and 0/100 percent. The seed was untreated or treated with Celest Extra Formula M ( CEFM, difenoconazole + fludioxonil) or Celest Formula M (CFM, fludioxonil). In the field trials using untreated seed, there were significant differences between infection levels only for some agronomic characters and levels. Fungicide seed treatment with CEFM in spring wheat had no significant effect on most agronomic characters including yield. In winter wheat and oats, seed treatment with CFM increased yield by 7-11% and plant density by up to 33% while having no effect on other characters. The percentage discoloration of crown roots and stem bases due to Fusarium/Microdochium spp. was also investigated visually in winter wheat and oats and found to increase with higher infection level. Fungicide seed treatment thus mainly increased plant emergence in seed lots with low-to-moderate Fusarium/Microdochium spp. infection and had little or no effects on other agronomic characters.