Head smut [Ustilago bullata] of grasses on the Canadian prairies: distribution, impact, and control
1995
Gossen, B.D. | Turnbull, G.D.
Production of meadow bromegrass (Bromus riparius), a recently introduced forage grass, is increasing rapidly on the Canadian prairies. A study was undertaken to examine the effect of head smut [Ustilago bullata] on this new crop. U. bullata was present in over 60% of the meadow bromegrass seed fields examined in Saskatchewan and Alberta. It occurred frequently where susceptible grass species were dominant; in 65% of the sites dominated by downy brome (B. tectorum) or foxtail barley (Hordeum jubatum), in 45% of sites dominated by Japanese brome (B. japonicus), but in only 5% sites where slender wheatgrass (Elymus trachycaulus) predominated. It was not found on crested wheatgrass (Agropryon cristatum) or smooth bromegrass (B. inermis). Incidence was generally low, but 95% of downy brome plants at one site were infected. At many sites, several host species were present but only one was infected. This result indicates that several pathotypes may exist in the region. Seed treatment with the fungicides carbathiin, captan, thiram, propiconazole, and hexaconazole all controlled head smut in greenhouse and field trials and there was no evidence of phytotoxicity. Storage of smut spores and infected seed for up to one year at temperatures from -7 to 36 degrees C did not influence survival and germination of smut spores or incidence of smut in plants grown from infected seed. Smutted plants suffered greater winterkill than healthy plants in one year out of three, and exhibited reduced incidence and severity of smut symptoms in two of three years.
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