Plant Disease Management Handbook

Cause Septoria spp. (teleomorph: Mycosphaerella) or Stagonospora spp. (teleomorph: Mycosphaerella), fungi that survive winter and summer as mycelia or pycnidia (minute, black, flask-shaped fungal structures) in infected debris. These fungi attack a broad range of hosts, including bentgrass, bluegrass, fescue, and ryegrass. Bluegrass is more susceptible than other grasses.

Cause The fungi, Fusarium sambucinum, F. culmorum, and F. avenaceum, have been found on orchardgrass plants in Oregon seed production fields. Other Fusarium species are known to pathogenic on turf grasses: F. acuminatum, F. crookwellense, F.

Cause At least two species of Rhynchosporium scald fungi. Rhynchosporium orthosporum infects bentgrass, fescue, orchardgrass, ryegrass, and bluegrass; R. secalis is best known as the cause of scald in barley, but it can also infect bentgrass and ryegrass. Rhynchosporium scald is one of the more common causes of leaf spot on orchardgrass, perennial ryegrass, and tall fescue in winter and spring.

Cause A bacterium, Rathayibacter rathayi (formerly Corynebacterium rathayi), that is seedborne in orchardgrass and survives in affected debris and soil. It does not spread rapidly through a field or appear to affect seed yield except in years with heavy rain during orchardgrass heading. Rathayibacter depends on the Anguina sp.

Cause Mastigosporium rubricosum, a fungus that overwinters as mycelium in infected leaves and affects orchardgrass, bentgrass, and timothy. Conidia develop from overwintered mycelium and are disseminated in water and wind. The fungus requires cool, wet weather to infect hosts. The disease is most severe in the cold, rainy, or foggy weather of winter and early spring.

Cause A fungus, Blumeria graminis (syn. = Erysiphe graminis; anamorph Monilia hyalina), that overwinters on infected plants or as chasmothecia associated with debris and is most commonly observed on tall fescue, fine fescue, and Kentucky bluegrass but all cool season grasses are susceptible, including native perennial grasses. Spores can be dislodged easily and spread by wind.

Cause Several species of the nematode genus Anguina can affect orchardgrass, annual ryegrass, bentgrass, and fescue. Recent DNA studies point to the likelihood of a different Anguina species evolving on each susceptible grass genus. These studies also suggest that Anguina agrostis may be limited to infecting only bentgrass. DNA testing can be used to identify the Anguina nematodes to species.

See:

Grass for Seed - Head Smut (Loose Smut)

See:

Grass for Seed - Kernel Smut

Cause Puccinia crandallii, a fungus that survives from season to season on infected plants. Red, Chewing's, and sheep fescue are susceptible. The alternate host for fine fescue rust is snowberry (Symphoricarpos spp.), a common plant throughout the West. Primary inoculum is urediniospores; secondary inoculum (urediniospores) is produced in initial pustules and disseminated by wind.