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SYMPTOMATIC KEY TO DISEASES OF KENTUCKY BLUEGRASS,PERENNIAL RYEGRASS AND FINE LEAF FESCUE TURFS

Adapted from University of Marylandhttp://iaa.umd.edu/umturf/Diseases/diagnose.html

SPOTS ON LEAVES OR LEAF SHEATHS

DISEASE

SEASON

PRINCIPLE HOSTS AND COMMENTS

Leaf spots brown or purple-brown, oval shaped or elongate. The centers of spots may develop a tan colour. Turf may be thinning-out in irregular patterns.

Helminthosporium leaf spot

Spring, summer, fall; most common in spring

All turfgrasses, especially common-type cultivars.

Leaf spots are hour-glass shaped, bleached white, tan or straw-brown in colour and extend across the entire width of the blade. Leaf lesions are normally bordered by brown, purple or black bands. Affected patches are circular and 2" - 6" in diameter. Foliar mycelium may be evident with a heavy dew in the morning

Dollar spot

Spring, summer, fall; most common in May and June

All turfgrasses, especially poorly nourished turfs.

AFFECTED AREAS DEAD OR THINNING IN CIRCULAR PATCHES, SPOTS OR RINGS

 

 

 

Circular patches of matted leaves appearing late fall, winter, or early spring. Generally appearing at snow melt or in the presence of plenty of surface moisture during cool-cold overcast periods.

 

 

 

1. Patches 1" - 6" diameter; matted leaves have a pinkish or red-brown colour. Center of patches may be bleached white in colour.

Pink snow mold

Late fall, winter, spring; especially spring

All turfgrasses, especially annual bluegrass, perennial ryegrass, and tall fescue.

2. Patches 6" - 3' diameter; matted leaves have a greyish colour. Sclerotia may be present.*

 

Gray snow mold

Late winter and early spring

All turfgrasses, especially Kentucky and annual bluegrass, and tall fescue.

*Sclerotia are compact masses of fungal mycelium covered with a protective rind. Gray snow mold sclerotia are chestnut brown or black in colour, 1/8 - 3/16 inches in diameter, and are usually found embedded in sheaths or on leaves of diseased turf during spring following snow melt.

 

 

AFFECTED AREAS DEAD OR THINNING IN CIRCULAR PATCHES, SPOTS OR RINGS (continued)

DISEASE

SEASON

PRINCIPLE HOSTS AND COMMENTS

Circular, straw-brown spots 2" - 6" in diameter. Straw-brown or white, hour-glass shaped lesions on leaves.

Dollar spot

Spring, summer, fall

All turfgrasses, especially poorly nourished turfs.

Circular or irregular patches 3" - 12" in diameter. Leaves watersoaked and covered with a pink gelatinous fungal growth. Dead leaves in center of affected areas straw brown, tan or slightly pinkish in colour. Red, brittle, thread-like strands extending from tips of dried grass blades.

Red thread

Primarily spring and fall, and prolonged rainy periods in summer

All turfgrasses, especially perennial ryegrass and fine leaf fescues.

Circular patches 6" - 2' in diameter. Affected areas brown; outer margin of diseased patches may have a greyish "smoke ring." Leaves blighted and oval to elongated, chocolate-brown lesions present. Foliar mycelium evident during early morning when dew is present.

Rhizoctonia brown patch

June-Sept. Normally occurring when night temperatures are above 68 degrees F, high day temps., and high relative humidity.

All turfgrasses, especially perennial ryegrass and tall fescue.

Circular or irregular patches or rings, sometimes rings with living grass in center ("frog eyes"). Patches initially 1" - 2", increasing to 6" - 2' in diameter. Patches may be sunken and leaves at the periphery may have a yellow-orange or bronzed appearance. Tip dieback of leaves giving turf a straw-brown colour.

Summer patch

July-early Sept.

Primarily Kentucky bluegrass and fine leaf fescue turfs.

Circular spots 1" - 3" diameter, leaves are greyish or water-soaked, and mycelium is normally present on leaves during early morning hours. Leaves are rapidly blighted and entire plants die in 24 hours. Dead plants in affected spots are brown or red-brown in colour, and matted.

Pythium blight

July-early September

Primarily perennial ryegrass especially during hot and humid periods, and in poorly drained sites. Seedlings of all species planted during warm and humid periods are susceptible.

Rings or arcs of dead grass bordered by inner and outer zones of dark green grass; or rings of luxuriantly growing grass without a dead zone. Rings 1 - 4 feet in diameter or larger. Mushrooms, growing in ring, may be present following rainy weather.

Fairy Rings

All year, especially summer

All turfgrass, especially droughty sites and poorly nourished turf.

AFFECTED AREAS DEAD OR THINNING-OUT IN AN IRREGULAR PATTERN

 

 

 

Turf thinning-out and brown or red-brown in appearance from a distance. Brown or purple-brown, oval-shaped leaf lesions on leaves and sheaths.

Helminthosporium melting-out

Primarily during wet, overcast periods in spring and fall.

All turfgrass, especially poorly nourished or excessively fertilized common-types of Kentucky bluegrass and red fescue.

Leaves bearing parallel black or silvery-grey stripes that extend the length of leaves. Leaves eventually shred and curl along lines releasing black, powdery spores masses. Leaves may be yellow.

Stripe or Flag smut

Symptoms noted spring and fall, but turf may succumb during hot, dry periods in summer.

Primarily Kentucky bluegrass older than 3 years of age.

Leaves bearing red, orange, yellow or black pustules. Turf has a yellow or reddish appearance from a distance.

Rust

Primarily late summer and fall

All turfgrasses, especially perennial ryegrass, Kentucky bluegrass, and zoysiagrass.

MOLD OR OTHER RESIDUES ON LEAVES

 

 

 

Grey or black, cigarette ash-like residue on leaves. Crusty material (fruiting structures) is easily rubbed off and appears after a prolonged rainy period. Moldy residue may form on plants in rings or arc patterns.

Slime mold

Spring, summer and fall, especially after prolonged rainy periods

All turfgrasses.

Leaves with black or silver-grey stripes that rupture causing leaves to shred and curl; releasing black, powdery spore masses.

Stripe or flag smut

Primarily spring and fall

Primarily Kentucky bluegrass and zoysiagrass.

Leaves bearing red, orange, yellow or black pustules. Turf yellow or reddish in appearance from a distance.

Rust

Primarily late summer and fall.

Primarily perennial ryegrass, Kentucky bluegrass and zoysiagrass.

Leaves bearing a whitish or grey moldy growth. Leaves eventually turning yellow.

Powdery mildew

Spring to fall; primarily late summer and fall

All turfgrasses, especially Kentucky bluegrass. Normally occurring on turf in shaded environments.

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