Spring Through Fall
Summer
Fall Through Spring (Cold, Moist Conditions)

Summer
Brown Patch: Prevalent during moist, hot weather on overfertilized lawns.

Look for: Dark, water-soaked-looking grass turning into browned-out, circular areas, several inches to several feet in diameter. Frequently some green leaves persist within the patch, and roots remain intact. Blades may have irregular ash gray lesions with a dark brown margin running along one side. On short turf, a 2-inch unsightly "smoke right" of gray mycelium may encircle the patch in early morning. running along one side bordered by a dark-brown margin.

Management: Use improved cultivars, such as ryegrasses 'Repell III' and 'Prelude III,' 'Scaldis' fine fescue, or 'America' bluegrass, and use a slow-release nitrogen fertilizer. Water deeply but infrequently, mow high, remove excess thatch, and improve aeration and drainage.

Dollar Spot: Affects low-nitrogen lawns, especially when stressed by drought and when heavy dews are prevalent.

Look for: Mottled, straw-colored 4- to 6-inch patches on lawns with taller grass. Grass blades have light tan bands with reddish brown margins spanning across them. Patches may merge to form large, irregular areas. Grayish white cobwebby mycelium may be present in early morning.

Management: Overseed with a blend of improved cultivars such as the bluegrass 'Adelphi,' perennial ryegrass 'Manhattan III,' and fine fescue, 'Reliant.' Maintain adequate nitrogen and potassium fertility, water deeply when necessary, and remove excess thatch. If your grass is prone to Dollar Spot, remove morning dew by dragging a hose across the lawn. 

Pythium Blight: A serious, rapidly spreading disease involving entire grass plant, Pythium blight occurs on poorly drained soils that have a wet grass canopy. Look for it when nighttime temperatures plus relative humidity equals 150.

Look for: Sudden appearance of 1- to 6-inch reddish brown, wilted patches, which turn to streaks as they enlarge along drainage patterns. In early morning, the grass is slimy, dark, and matted. White cottony mycelium may be present when the grass is wet. As it dries, the grass turns light tan and shrivels.

Management: Improve drainage and air circulation, avoid overwatering, aerate, reduce excess thatch, and avoid nitrogen fertilizer during warm weather. Check calcium levels and add lime if deficient. Observe closely for spread and consult your Cooperative Extension Service if the disease progresses. 

Rust: Appears on low fertility, compacted, or shady lawns when growth slows during hot, dry weather.

Look for: Initial small yellow flecks develop into pustules releasing yellow, orange, red, or dark brown spores. From a distance, the turf appears orange or yellow, and colored spore residue rubs off if touched.

Management: Use rust-resistant cultivars of ryegrasses such as 'Palmer III' and 'Repell III' and new cultivars of Kentucky bluegrass such as 'Challenger' and 'Eclipse.' Provide appropriate fertilization and irrigation, prune low-hanging tree branches to reduce shade, maintain aeration, and mow frequently, bagging clippings.