This can present problems when homeowners or turf managers are trying to establish new turf stands. Newly seeded tall fescue and perennial ryegrass can be thinned due to brief outbreaks of Pythium blight. New stands are especially vulnerable when high seeding rates, heavy nitrogen fertilization and overwatering are used. Symptoms Blight Symptoms Unlike dollar spot, rust or powdery mildew, where only the foliage is damaged and plants often recover quickly, Pythium-blighted plants usually die. Recovery of blighted turfs from rhizomes or stolons that fill in from outside areas or from germination of annual bluegrass seed is slow and normally doesn't occur until the onset of cooler weather.
Diseased area begins with small reddish-brown spots.
The sudden appearance of large, irregular or circular patches probably are not symptoms of Pythium blight, but more likely those of brown patch, summer patch or necrotic ring spot. Pythium blight may occur in streaks conforming to surface drainage patterns, in localized low spots where water puddles, or in larger areas where the individual spots have coalesced. The spots developing on higher cut lawns or fairway turfgrass tend to be larger and more irregular in shape than those occurring on golf greens and tees where the turf is cut short. White fungal mycelium that resembles a cotton ball. In the morning dew, infected grass leaves appear water-soaked, slimy to the touch, and dark green.