Is a type of fungus and a turf disease that damages or kills grass after snow melts, typically in late winter. Its damage is usually concentrated in circles three to twelve inches in diameter.
The disease occurs from early spring through late fall, but is most active under conditions of high humidity and warm daytime temperatures 59–86 °F and cool nights in the spring, early summer and fall.
This disease causes circular lesions to appear on the blades of your grass. If lesions remain on your grass for long periods of time, the blades will start to become yellowish and shriveled. This often gives grass the appearance of being dehydrated.
Rust tends to thrive in relatively moist areas where the days are warm and humid and the nights are cool and dewy.
Spring dead spot symptoms appear in circular patches from 6 inches to several feet in diameter that remain dormant as the turf greens up in the spring. These patches eventually die and collapse to the soil surface.
First appear as small, irregularly shaped spots and will join together to form large patches that will often be long streaks. The leaves will at first look and feel water-soaked, greasy, or slimy. Once dew or moisture dries up the blade will shrivel up and collapse, often causing a matted brown turf. With high humidity in early morning or throughout the day, diseased leaves may be covered with the white, cobwebby, mold like.
"Frog-eye" patterns occur in the lawn; these are small circles of dead grass with a tuft of green grass surrounding and enclosing them. Infected leaves turn reddish purple.
First symptoms are light patches of dusty, white to light gray growth on grass blades, especially during cool, rainy weather. Lowest leaves may become completely covered. Although generally not too serious a problem, it can become severe if not controlled. Heavily afflicted areas look as though they've been covered with lime or flour or sprayed with a coat of white paint.
Small spots that appear water-soaked enlarge rapidly to cover a large part of the leaf. As the spots dry, the leaves fade to a light brown or tan. Pink webs bind the grass blades together. Later, the fungus forms thin, red-to-pink, finger-like structures at the tips of grass leaves, which gives the lawn a reddish cast.