Common Lawn Diseases
Small, circular spots from 1-5 inches in diameter; spots might merge to form large, irregular areas; leaves appear water soaked then brown, often exhibiting a reddish band across the leaf; fine, white cobwebby threads seen in early morning.
A dark green band of turf develops in a circle (4 inches up to 30 feet) or semicircle in moist turf; mushrooms might or might not be present; an area of brown, dying grass might occur just behind the dark green band; a second ring of dying grass might appear inside the circle; weeds commonly invade.
Small, circular, grayish green areas, ranging from a few inches up to a foot in diameter; some plants in center can survive, giving a frog-eye appearance; the crown or basal area of dead stems has a reddish rot and is hard and tough; dead foliage appears bleached.
Gray Leaf Spot:
Irregular blighted patches of turf with bleached spots with dark margins on leaves; ryegrass develops a fishhook appearance.
Microdochium Patch (Pink Snow Mold):
Circular patches of 1-2 inches that can enlarge to 12 inches; leaves first appear water soaked, then reddish brown, and finally bleached; minute, gelatinous spore masses sometimes seen on dead leaves; white or pinkish fungal threads might be seen in early morning; more prevalent in Central and Northern California.
Circular to elongated brownish spots with brown centers and dark brown or purple borders on leaf blades, sheaths, and stems; crowns and roots frequently have a dark brown rot; crown-infected plants might die in hot, windy weather, leaving thinned areas throughout the turf; spores are windborne.
Pythium Blight (Grease Spot):
Small, circular spots (2-6 inches) that run together; blackened leaf blades rapidly wither, turn reddish brown, lie flat, stick together, and appear greasy; roots might be brown; in humid conditions, masses of fungal mycelium might appear.
First appears as small, irregular brown patches or rings that can enlarge to many feet in diameter; centers might recover resulting in rings of diseased grass; leaves and sheaths become water soaked, wilt, turn light brown, and die; in light infestations, roots usually not infected and plants often recover; soil-inhabiting fungus that forms fine, fungal threads in soil or on turf grass.
Rhizoctonia Large Patch:
First appears as small, irregular brown patches or rings that can enlarge to many feet in diameter; centers might recover resulting in rings of diseased grass; leaves and sheaths become water soaked, wilt, turn light brown, and die; plants pull out easily from soil with rotten stolons, in light infestations, roots usually not infected and plants often recover; soil-inhabiting fungus that forms fine, fungal threads in soil or on turf grass.
Circular, yellow or tan areas of dead and dying plants up to 1 foot in diameter; can have green, apparently healthy plants in center; roots, crowns, and stolons have dark brown fungal hyphae on them; vascular discoloration and cortical rot occur in later stages.
Spring Dead Spot:
Circular areas of dead grass 6-12 inches in diameter appear in spring when growth resumes; spots might coalesce to form large areas; typically affects turf grass more than 2 years old.