Identify lawn diseases that commonly impact lawns in Minnesota.

Symptoms:

• Rings or patches of blighted turfgrass that measure 5 inches to more than 10 feet in diameter.
• Leaf spots and "smoke rings" - thin, brown borders around the diseased patches that appear most frequently in the early morning.

Conditions Favoring Disease:

• Active at cool temperatures on warm-season grasses in the spring and fall (over85F during the day and over 60 F at night).
• Occurs in areas that experience extended periods of wetness.

Symptoms:

• Symptoms vary with causal agents.
• Aboveground mushroom and puff ball basidiocarps may or may not occur.
• Typically has outer rings that are either dark-green or brown in color.
• Shape and size of rings vary depending on the species.
• Activity in turf ceases when the individual rings come in contact with each other.
• Some causal agents form fruiting bodies, but not rings and vice versa.

Conditions Favoring Disease:

• Typically occurs in the summer.
• Can also occur on cool-season turfgrass in mild winter climates

Symptoms:

• Evident after snow melts.
• Light brown, gray, or strawcolored patches 10 inches in diameter.
• Patches can increase to several feet and coalesce
• Rust-, brown-, or black-colored sclerotia also appear on the infected leaves.

Conditions Favoring Disease:

• Snow cover, especially snow that lasts more than 90 days.

Symptoms:

• Purplish-brown to black spots with tan centers on the leaf blade and sheath.
• Lower leaves of infected plants become shriveled and blighted.
• In severe cases, almost all of the leaves and tillers die.
• Typically follows the appearance of leaf spots on cool-weather turfgrass.

Conditions Favoring Disease:

• Temperatures between 40°F and 80°F.
• Areas with 10 hours a day of foliar wetness for several consecutive days.
• High amounts of nitrogen and a low mowing height.

Symptoms:

• Sunken, circular patches that measure several inches
• Patches turn from brown to straw color and may eventually coalesce, forming irregularly shaped areas.
• May display small lesions that turn from yellow-green to straw color with a reddishbrown border.
• Lesions can extend the full width of the leaf.

Conditions Favoring Disease:

• Continuous high humidity at temperatures between 59°F to 86°F.
• Favored by warm days, cool nights, and intense dews.
• Infects areas with low levels of nitrogen.
• More severe in dry soils.

Symptoms:

• Yellow or reddish-brown patches 1 inch to 6 inches in diameter
• Periphery of patches are reddish-brown or pink in color.
• “Smoke rings”—thin, brown borders around the diseased patches that appear only in the early morning—can occur.

Conditions Favoring Disease:

• Thrives in temperatures less than 60°F in wet conditions.
• Infects areas with slow growing conditions and heavy thatch.
• Microdochium nivale is termed Fusarium patch when it occurs in the absence of snow cover.

Symptoms:

• Rings or patches of blighted turfgrass that measure up to 10 feet in diameter.
• Leaf spots, blighted rings and patches and “smoke rings”—thin, brown borders around the diseased patches that appear most frequently in the
  early morning.
• Blackened or rotted sheaths and stolons of turfgrass near the soil layer.

Conditions Favoring Disease:

• Active at cool temperatures on warm-season grasses in the spring and fall (77° to 83°F canopy temperatures).
• Occurs in areas that experience extended periods of wetness or low areas subjected to standing water.

Symptoms:

• Yellow, tan, or salmon-colored water-soaked patches that measure 1 to 8 inches or more in diameter.
• Pale pink around the edges.
• Spores are produced in white or salmon-colored sporodochia that are found on the dead tissue.
• Blighting can occur in streaks from spores tracking on the equipment wheels.

Conditions Favoring Disease:

• Favors temperatures of less than 60°F.
• More severe where snow has fallen on unfrozen soil or in cold, rainy weather.
• Microdochium nivale is commonly called Fusarium patch in the absence of snow cover—but the causal organism is the same.

Symptoms:

• First appears as thinned yellow to light-green circular patches that are 3 to 15 inches in diameter.
• Can expand up to 3 feet in diameter.
• Eventually turn brown or straw-colored and die.
• Roots and rhizomes of the affected turfgrass turn brown to black.
• “Frog-eye”—a symptom where less susceptible grass species survive inside the diseased patch—can also occur.

Conditions Favoring Disease:

• Initiates in moist soil.
• More severe in higher temperatures (of up to 80°F) and drought conditions.
• Seeded sites, as well as sodded sites in newly cleared woodlands, are susceptible.
• Found in areas with compacted soil and that are high in nitrogen during the spring and summer.

Symptoms:

• Appears suddenly during hot, humid weather.
• Greasy, brown circular spots that are initially about 3/4 inch to 2 inches in diameter.
• Rapidly enlarges in size
• Water-soaked and dark-colored early in the morning.
• Forms fluffy white masses of fungal mycelium (cottony blight) and can coalesce to form large, irregular areas of dead turf.
• Infected patches may appear bronzish-orange in color.

Conditions Favoring Disease:

• Found in areas with poor drainage and air circulation as well as in locations that are high in salinity or nitrogen.
• Favors night temperatures of over 68°F.
• Occurs in areas that experience more than 10 hours a day of foliar wetness for several consecutive days.

Symptoms:

• Light yellow flecks initially on the leaf blades and sheaths.
• Flecks enlarge, elongate, and turn yellow in color.
• Infected areas rise above the epidermis and then rupture, releasing spores that are yellowish-orange to reddishbrown in color.
• Leaf blades turn yellow, starting at the tip and progressing to the base sheath.
• Severe disease infection can cause the shoot to turn yellowish to reddish-brown in color and slow in growth.
• Turf may appear thin as individual shoots die.

Conditions Favoring Disease:

• Typically occur in early spring through fall, depending on the location of the turf.
• Favors low-light areas.
• Depending on the species, rusts favor temperatures between 65°F and 86°F.
• Severe rust infections occur on slow-growing turfgrass, particularly those with low nitrogen levels and/or plant water stress.

Symptoms:

• First appears on the leaves as individual tufts of fine, white mycelium.
• The tufts enlarge and coalesce, causing the leaves to have a grayish-white or powdery appearance.
• Severely infected turf turns yellow, then tan and brown in color.
• Stressed turf that is severely infected can die.
• Severely infected turf, especially in shaded areas, can become thinned.

Conditions Favoring Disease:

• Favored by humid, cloudy weather with temperatures between 60°F and 72°F.
• Occurs in areas under stress.
• Low light and high humidity
• Common in areas with poor air circulation, but does not require a film of water to infect turf.

Symptoms:

• Patches that are reddish-brown in color and 1 to 4 inches in diameter up to 2 feet.
• Causes a gelatinous mass of pink mycelium with watersoaked leaves.

Conditions Favoring Disease:

• Temperatures between 40°F to 85°F and in locations that are low in nitrogen.
• Areas that experience more than 10 hours a day of foliar wetness for several consecutive days
• Pink patch usually develops in the presence of red thread.
• The two diseases often occur under the same conditions and at the same times.