Tall Fescue Online Monograph

Disease and causing organisms 

Signs 

Brown patch

(Rhizoctonia spp).

Large brown patches up to 0.9 m (3 ft) in diameter develop during warm, moist weather; large purplish-green or tan lesions appear on infected leaves; grayish mycelium may cause a "smoke ring" to appear at the margin of each patch.

Curvularia blight

(Curvularia spp.)

Irregularly shaped patches of blighted turf first appear yellow and mottled, then brown; individual leaves appear flecked or yellow-green and discolor from the tip to the sheath.

Dollar spot

(Lanzia spp. and Mollerdiscus spp.)

Small, round bleached spots about 2.5-7.6 cm (1-3 in) in diameter appear in closely mowed turfs; larger patches of yellowed turf appear in turf maintained at a higher cutting height; light tan lesions with distinct darkened margins develop on individual leaves; when dew is present, white, web-like mycelium may be visible on lesions.

Fairy rings

(Marasmius spp., Lepiota spp., and Psalliota spp.)

Small to large circles of dark green or dead plants develop; mushrooms or puffballs may also appear in the infected rings; soil in each ring may be difficult to wet (hydrophobic).

Gray leaf spot

(Pyricularia grisea)

Small, round gray-brown lesions appear on leaf blades and sheaths; as the lesions increase in size, their centers often turn from light brown to gray and purplish-brown margins form; as infection progresses, leaves yellow, then wither and die; immature turfs are especially susceptible.

Helminthosporium diseases

(Bipolaris spp., Drechslera spp., and Exserohilum spp.)

Helminthosporium leaf spot diseases cause small, brown, and circular lesions; lesions eventually may enlarge and girdle leaves, causing plants to appear light brown or tan; turf may ‘fade out' or thin when fungi attack crowns and roots; these fungi often attack turfgrass seedlings.

Pink snow mold

(Microdochium nivale)

Circular, light tan, or gray patches develop during cold, wet weather; small patches may enlarge to about 0.6 m (2 ft) in diameter with snow cover; patches seldom exceed 15 cm (6 in) in diameter without snow cover; infected turf appears pink or salmon in color when exposed to sunlight.

Pythium blight

(Pythium spp.)

Hot, wet weather and excessive irrigation favor the development of this blight; the disease usually appears in summer as small, circular patches of wilted turf; cottony-gray mycelium often is visible in diseased areas; the disease can spread rapidly, infecting plants in low areas and along drainage channels; several Pythium species also are responsible for root-rot type diseases.

Red thread

(Laetisaria fruciformis)

Reddish or bleached patches rapidly develop during cool, moist weather; infection usually spreads from the leaf tip toward the sheath; reddish mycelium may cover affected leaves and small "threads" may bridge plants.

Rusts

(Puccinia spp. and Uromyces spp.)

Small, yellow flecks first appear on leaves and stems; spots on infected leaves often increase in size and have raised centers; eventually, these rupture, exposing masses of yellow, orange, red, or brown microscopic spores.

Slime molds

(Mucilago crustacea, Physarum spp. and Fuligo septica)

Extended periods of warm, moist weather favor disease development; small, fruiting bodies of these fungi vary in color (white, yellow and gray); although fungi may cover leaves, they do not attack leaf tissue and are not considered harmful.

Stripe smut

(Ustilago striiformis)

Infected plants are stunted and appear pale green to slightly yellow or brown; leaves often become rigid and may split or curl.

Take-all patch

(Gaeumannomyces spp.)

Patches of blighted, dull to bright reddish-bronze turfgrasses may reach more than 0.6 m (2 ft) in diameter; as disease-resistant plants fill the center, each patch resembles a frog eye; patches eventually fade from reddish-bronze to tan and often coalesce, forming large, irregularly shaped patches of dead turf.

White patch

(Melanotus spp.)

Bleached patches of tall fescue, 0.3-0.6 m (1-2 ft) in diameter, are distinctly white; small, white mushrooms are visible on leaf blades; damage usually progresses from the leaf tip to the sheath.

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Tall Fescue Monograph