Fusarium head blight is not a common disease in tall fescue. When present, it is characterized by bright orange-colored sporodochia on panicles and seeds. The fungi, Fusarium heterosporum Nees:Fr. (Foudin and Calvert, 1982; Schoen and Hurst, 1986) and F. culmorum (W.G. Smith) Saccardo (Holms, 1983), cause head blight. The sporodochia of F. heterosporum have been observed during seed testing and may be responsible for reduced seed germination observed during germination tests (Schoen and Hurst, 1986). Predominant Fusarium spp. isolated from tall fescue seeds produced in Oregon include F. avenaceum (Corda: Fr.) Saccardo, F. culmorum, F. pseudograminearum O'Donnell & T. Aoki, and F. sambucinum Fuckel, and inoculations of tall fescue panicles with F. avenaceum and F. pseudograminearum significantly lowered germination rates of the harvested seed crop (Ocamb and Alderman, 2004). Seed can be infected without visible sporodochia. Seed decay and damping-off may be apparent in the field, characterized by poor stand establishment.

All species of Fusarium produce macroconidia and many species, including F. culmorum, F. pseudograminearum, and F. sambucinum, produce chlamydospores. Macroconidia are sickle-shaped spores, generally 3- to 5-septate, with characteristic spore shape and size on carnation leaf agar. Chlamydospores are thick-walled spores that can survive in soil for many years. Many Fusarium spp. also produce ascospores, and sometimes perithecia can be found on plant debris, such as stems of grass seed plants.

These Fusarium species are distributed widely and cause disease on many species of grasses and cereals (Smiley et al., 1993). Mycelium of Fusarium spp. can colonize leaf or below-ground tissues, as well as plant debris. Fusarium spp. generally overwinter as chlamydospores or mycelia. Conidia are produced on mycelia, especially when colonized debris are remoistened by rain, heavy dew, or fog.


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