Brown Patch

SEASON: Mid - to late summer.

APPEARANCE: Large, irregular circular areas, up to several feet in diameter, occur throughout the lawn. The patches usually have a brownish to gray discoloration with a water-soaked appearance around the edges. Normally, only the leaves and stems are attacked.

FAVORABLE CONDITIONS: It attacks Kentucky Blue, bentgrass, Bermuda grass, ryegrass, fescue, and zoysia grass.

RESISTANT VARIETIES: 'Manhattan II', and 'Pennant' perennial ryegrasses; 'Rebel II' and 'Wrangler' tall fescues.

Dollar Spot

SEASON: The disease occurs from spring through fall, and is most active during moist periods of warm days (70-85°F) and cool nights (60°F) in the spring, early summer and fall.

APPEARANCE: Dollar spot symptoms vary depending primarily on turfgrass species, mowing height and nutrition level. Overall appearance of dollar spot on closely mowed bentgrass golf greens differs from that observed on taller Kentucky bluegrass, fine fescue and perennial ryegrass turfs.

FAVORABLE CONDITIONS: Several factors influence the occurrence and severity of dollar spot. Bentgrass, hybrid bermudagrass and zoysia are most susceptible; while St. Augustine and centipede are less frequently attacked by dollar spot.

Fusarium Patch

Pink Snow Mold

SEASON: Fall to spring.

APPEARANCE: Circular patches, 1 to 8 inches in diameter; tiny white or pink masses are sometimes seen on dead leaves. Fungal threads, also white or pink, become visible in early morning. Blades of grass are light tan and stick together. Small, white, or pinkish gel-like spore masses are occasionally seen on dead leaves. This disease is called pink snow mold if it develops under snow or at the margins of melting snowbanks.

FAVORABLE CONDITIONS: Cool (40° to 60° F) temperatures and moisture.

SUSCEPTIBLE GRASSES: Ryegrass, fescue, zoysia grass, colonial and creeping bentgrass.

RESISTANT VARIETIES: 'Medallion' and 'Scaldis' fine fescues, 'Eclipse' and 'America' Kentucky bluegrasses, 'Manhattan II' and 'Pennant' perennial ryegrasses.

Leaf Spot

SEASON: Spring to Fall.

APPEARANCE: The most obvious symptom of this disease is elongated circular spots on the grass blades. These spots have a brown or straw-colored center with black to purplish borders.

FAVORABLE CONDITIONS: Cool (50° to 70° F), moist conditions are most favorable for the growth of leaf spot. The spots first appear on grass in shady areas of the lawn. They occur most commonly during wet, humid weather or in lawns that are often lightly sprinkled or mowed too closely.

SUSCEPTIBLE GRASSES: Kentucky bluegrass, fescue, and Bermuda grass.

RESISTANT VARIETIES: 'Julia' and 'Midnight' Kentucky bluegrasses, 'Banner II' fine fescue, 'Cimarron' and 'Rebel II' tall fescues.

Necrotic Ring Spot - NRS

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 (58° to 82° 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.

Powdery Mildew

SEASON: Early summer to fall.

APPEARANCE: 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.

FAVORABLE CONDITIONS: Slow or non-existent air circulation, shade, and high humidity with temperatures of 60° to 70° F.

SUSCEPTIBLE GRASSES: Kentucky bluegrass, zoysia grass, and Bermuda grass. Lawns growing rapidly because of excessive use of nitrogen fertilizer are extremely susceptible.

RESISTANT VARIETIES: 'Cindy' and 'Flyer' red fescues, 'America' and 'Chateau' Kentucky bluegrasses.

Pythium Blight

SEASON: Summer.

APPEARANCE: The first indication of this disease is the occurrence of irregular patches a few inches in diameter. In those areas, the grass blades appear water-soaked, soft and slimy. The blades soon wither and fade to light brown or straw color, sometimes reddish brown, particularly if the weather is sunny and windy. Then the patches join to form large damaged areas, often several feet in diameter. In the early morning, a white, cottony fungus can be seen on the blades of diseased plants.

FAVORABLE CONDITIONS: High temperatures and excess moisture.

SUSCEPTIBLE GRASSES: Tall fescue, bentgrass, Bermuda grass, Kentucky bluegrass, annual ryegrass.

Red Thread

SEASON: Fall.

APPEARANCE: 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.

FAVORABLE CONDITIONS: Most damaging in spring and fall in temperatures of 68° to 75° F and high humidity. Low levels of nitrogen favor its development. When the grass growth slows down due to a lack of nitrogen, the disease then becomes more prevalent.

SUSCEPTIBLE GRASSES: Red fescue, ryegrass, Kentucky bluegrass, and bentgrass.

RESISTANT VARIETIES: 'Biljart' and 'Claudia' fine fescues; 'Chateau' Kentucky bluegrass; 'Pennant' perennial ryegrass.

Rust

SEASON: Midsummer to Fall.

APPEARANCE: The lawn takes on a rust-colored cast, especially noticeable from a distance. Dust-like spores, the main symptom of this disease, form in circular or elongated groups on grass blades. Anything moving through a severely infested area will be covered by the spores, and may spread the disease.

FAVORABLE CONDITIONS: Moderately warm, moist weather. Dew that lasts for 10 to 12 hours promotes germination. Stress that restricts growth favors rust.

SUSCEPTIBLE GRASSES: Can affect most types of turfgrass, but Kentucky bluegrass is damaged most frequently.

RESISTANT VARIETIES: 'America' and 'Eclipse' Kentucky bluegrass, and 'Manhattan II' perennial ryegrass.