Fungal Communities and Disease Symptoms on Stem Bases of Wheat and Barley and Effects of Seed Treatments Containing Fluquinconazole and Prochloraz

Three successive crops of winter wheat or barley were grown as second, third and fourth cereals. Communities of fungi on shoot bases, identi®ed after isolation on agar media, were more diverse (determined by number of taxa identi®ed) on wheat than on barley, and their diversity increased from year to year. Diversity was not a€ected by seed treatments containing ¯uquinconazole or prochloraz. Eyespot (caused by Tapesia spp.) and brown foot rot (caused by Fusarium spp. or Microdochium nivale) increased from year to year. Eyespot, brown foot rot (after the ®rst year) and sharp eyespot (which remained infrequent), assessed in summer (June), a€ec- ted wheat more than barley. Eyespot severity was increased slightly on barley by treatments containing ¯uquinconazole, formulated with or without prochlo- raz, in the second year (third cereal), when it was also decreased slightly on wheat by ¯uquinconazole plus prochloraz, except in plots where the treatment had been applied for two successive years. The increases or decreases in eyespot in the second year were accompan- ied by, respectively, decreases or increases in the frequency of Idriella bolleyi where ¯uquinconazole was applied alone. Although the eyespot pathogen Tapesia yallundae (but not Tapesia acuformis) is sensitive to ¯uquinconazole in vitro, seed treatment, applied princi- pally to control take-all disease, is likely to have only a small e€ect against eyespot (or other stem-base diseases), and then only on wheat and when formulated with prochloraz. Introducti