During the summer, the turfgrass within the diseased areas begins to die, causing a general thinning of the lawn. The lawn also develops an uneven texture, which is most apparent after mowing. Eventually, thinning of the lawn will be very noticeable as weeds encroach into the dead areas. Infected plants, which are pale green to slightly yellow, may occur in patches, or may be scattered throughout the entire lawn. Individual leaf blades affected with the disease are slightly curled and have tattered or shredded tips, similar in appearance to damage caused by a dull mower blade.
Leaves also develop black sooty or powdery stripes which run parallel with the leaf veins.
The sooty substance is composed of millions of fungal spores. The presence of the black, sooty stripes on the leaves is diagnostic of smut. Infected plants often die during hot, dry weather, resulting in a thinning of the turf. In some cases, the symptoms disappear during the hot summer months, only to show up again in the cool fall weather. Stripe and flag smut survive adverse weather conditions inside infected plants or as resting spores in the soil.