• 7489 Hwy 60, Hartford, Wisconsin 53027

    262-673-7668

Lawn Disease Reference

 1) Snow Molds 

Occurrence:  Early to late spring
Favorable Conditions:  Cold wet weather with periods of prolonged snow cover over unfrozen ground often leading to the most severe damage
Grass Type:  Kentucky bluegrass, tall fescue, perennial ryegrass
Symptoms:  Circular, matted, gray to straw-colored patches ranging from a few inches to a foot or more in diameter
Management:  Remove leaf litter from lawns.  Mow lawns until dormant in the fall.  Avoid heavy fertilizer applications (greater than 0.5 lb. N/1,000 sq. ft.) late in the year.  Rake and lightly fertilize damaged areas in the spring to encourage recovery.  Reseed lawns as needed.

2) Necrotic Ring Spot 

Occurrence:  Spring, summer and fall
Favorable Conditions:  Cool (soil temperatures of 55 to 65oF) and wet conditions for infection, followed by heat and drought stress for symptom development; most severe when soil compaction limits rooting
Grass Type:  Kentucky bluegrass
Symptoms:  Circular, straw-colored patches usually less than 12 inches in diameter; regrowth often occurring in the center of patches, creating a “frog-eye” appearance; most common in newly sodded lawns, but also occurring in seeded lawns
Management:  Reduce soil compaction and improve lawn drainage.  Maintain proper fertility.

3) Fairy Rings
(many mushroom-forming fungi)

Occurrence:  Anytime
Favorable conditions:  Warm, wet weather; significant thatch accumulation
Hosts:  All cool-season lawn grasses
Symptoms:  Type I:  a ring or arc (up to several feet in diameter) of lush, dark green grass bordered by a band of dead turf, with or without mushrooms; Type II:  a ring or arc of lush dark green grass with no band of dead turf, with or without mushrooms; Type III:  a ring or arc of mushrooms with no band of lush green turf or dead turf
Management:  Lightly fertilize and routinely core aerate lawns.

4) Summer Patch

Occurrence:  Summer
Favorable conditions:  Hot, moist conditions; alkaline (i.e., high) soil and thatch pH
Grass Type:  Kentucky bluegrass, fine fescues
Symptoms:  Ring-like patches of wilted turf up to 3 inches in diameter, similar to those of necrotic ring spot (see above), and with rings often merging into larger irregular patches
Management:  Avoid excessive watering during hot periods.  Core aerate to promote root growth and reduce compaction.  Use acidifying fertilizers to lower thatch pH to below 6.5.

5) Dollar Spot

 

Occurrence:  Summer
Favorable conditions:  High humidity; low nitrogen fertility
Grass Type:  Kentucky bluegrass, perennial ryegrass, fine fescues
Symptoms:  Bleached patches ranging from a few inches to a foot in diameter, with leaf blades (inset) having bleached, hourglass-shaped areas
Management:  Water deeply and infrequently early in the morning to minimize prolonged periods of leaf wetness.  Apply nitrogen to alleviate symptoms.

6) Red Thread

Occurrence:  Spring through fall
Favorable conditions:  Wet, cool conditions
Grass Type:  Kentucky bluegrass, perennial ryegrass, fine fescues
Symptoms:  Irregular beige patches ranging from a few inches to a few feet in diameter (oftentimes merging into irregular patterns) with red, thread-like filaments among the grass blades
Management:  Collect clippings when disease is active.  Maintain adequate nitrogen fertility.

7) Rust

Occurrence:  Summer and fall
Favorable conditions:  High humidity, low soil moisture, low nitrogen fertility, shade
Grass Type:  Kentucky bluegrass, perennial ryegrass
Stand Symptoms:  Reddish-brown, powdery areas (masses of fungal spores) that can discolor clothing and equipment
Management:  Maximize light and airflow in lawns by pruning and thinning surrounding landscape plants.  Water and lightly fertilize.