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

Spring Through Fall
Fairy Rings: Caused by more than 50 varieties of fungus, the rings vary in size and appearance, but all form in soil high in woody organic matter, usually from buried debris or tree stumps.  

Look for: Rings of fast-growing, dark green grass with centers of weeds, thin turf, or dead grass. Midsummer and fall rings are more apt to be composed of dead grass.

Management: The rings are difficult to remove unless completely dug out to a minimum depth of one foot. Aerating ring area to improve water penetration and fertilizing to minimize color variation are helpful.

Stripe Smut: Causes yellowed, stunted growth in 6- to 12-inch patches.

Look for: Development of characteristic black stripes of erupted spores along grass blades that later become dry, shredded, and curled.

Management: Use resistant cultivars like the bluegrasses "Adelphi" or "Midnight." Maintain adequate fertilization. Water well, mow frequently, and bag clippings. 

Necrotic Ring Spot: Although the fungus is active during cool, moist periods, the damage frequently doesn't show until later, when turf is stressed.  

Look for: Circular "frog-eye" patterns of 6 to 12 inches with matted, straw-colored grass surrounding a tuft of green grass. As infection advances, roots and crowns may turn brown to black. Thatch may decompose in affected areas, giving them a sunken, or "donut," appearance.

Management: Overseed with disease-resistant cultivars of tall fescue and perennial ryegrasses, or use bluegrasses such as 'Classic', Eclipse', or 'Columbia.' In Canada, choose the bluegrasses 'Barblue', 'Nassau', 'Princeton', and 'Adelphi.' Water to lessen drought and heat stress. Avoid excessive fertilizer use. Remove excess thatch and maintain aeration and drainage. 

Drechslera Melting Out and Leaf Spot formerly Helminthosproium: Exhibiting two phases, this disease is especially destructive on overfertilized, lush bluegrasses. Cloudy, moist weather in the 70 to 85 deg. F range brings on the telltale leaf-spot phase.

Look for: Distinctive dark purple spots that develop into buff-colored oval lesions with a dark brown or purple margin. Blades progress to yellow and then turn tan. During the melting-out phase, rot develops in roots and crowns.

Management: Use resistant bluegrass cultivars such as 'Eclipse,' 'Nuglade,' 'Midnight,' 'Alpine,' 'S-R 2000,' or 'Princeton 104.' Avoid excessive nitrogen fertilizer, water infrequently but deeply, mow high, aerate, and remove excess thatch.