SEASON: Spring to fall.
APPEARANCE: "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.
FAVORABLE CONDITIONS: This fungus is the most active at relatively low temperatures (58º to 82º F), but dead spots may not become apparent until warm, dry periods in summer, when they seem to suddenly appear.
SUSCEPTIBLE GRASSES: The most susceptible is Kentucky bluegrass, particularly 'Arboretum', 'Fylking', 'Park', and 'Pennstar'. Bentgrass, creeping bentgrass, and fine fescues can also be attacked.
RESISTANT VARIETIES: None have been identified.