What are fairy rings?  Fairy rings are circular areas of abnormal turf growth that are most commonly found on lawns and golf courses where soils have high levels of organic matter, and in areas where trees have recently been removed.  Due to their mysterious, circular appearance, fairy rings have been of interest since ancient times.  According to medieval lore, they were thought to appear after a band of fairies had danced in an area.

What do fairy rings look like?  Fairy rings are rings of grass up to 15 feet in diameter that have a distinctly different color or texture than the grass inside or outside of the ring.  Half- or other partial ring patterns occur as well.  Depending on conditions, grass within fairy rings can be denser, greener, and faster growing, or alternatively browner and drier than surrounding grass.  During wet weather, rings of mushrooms may form at the edge of the discolored grass.

Where do fairy rings come from?  Fairy rings are caused by certain fungi that feed on decaying organic matter (e.g., tree stumps, logs, leaves or roots) buried in the soil.  Growth of fairy ring fungi begins in the center of the ring, expanding outward in a relatively uniform, circular pattern.  Three different types of fairy rings can form depending on soil type, the specific fungus involved, and environmental conditions.  Type 1 fairy rings occur most commonly on golf course putting greens, and occur less commonly on home lawns.  The fungi involved produce compounds that reduce the amount of water that the soil can absorb, leading to drought conditions that cause the grass in the ring to brown and die.  Type 2 fairy ring fungi efficiently decay organic matter releasing nitrogen that promotes lush growth and leads to a dense green ring of grass.  Finally, Type 3 fairy rings have rings of mushrooms that appear during wet periods, particularly in the fall.

What do I do with fairy rings in my lawn?  Fairy rings in home lawns do not typically cause turf death and thus are primarily cosmetic problems.  They often disappear naturally following a change in environmental conditions.  Therefore, waiting for fairy rings to naturally disappear is often the simplest option for management.

If you want to be more proactive in managing fairy rings, consider routine core aeration for your lawn.  Core aeration reduces the buildup of thatch which can harbor fairy ring fungi and make fairy ring development more likely.  If you are having a problem with Type 2 fairy rings, also consider applying a nitrogen fertilizer to the rest of your lawn to green up the surrounding grass to match the color of the fairy rings.  For Type 3 fairy rings, consider hand removing (wearing gloves) or raking up the mushrooms and disposing of them in your garbagethe mushrooms as they may be poisonous.  Finally, DO NOT use fungicides for control, as products labeled for use in managing fairy rings are typically not effective in preventing fairy ring development or reducing the severity of symptoms.

For details on core aeration and proper lawn fertilization rates and timings, see University of Wisconsin-Extension bulletin A3435, “Lawn Maintenance”.

For more information on fairy rings:  Contact your county Extension agent.

What is red thread? Red thread is a foliar disease of cool-season turfgrasses. Grass species affected by this disease include fine fescues (the species most commonly affected), tall fescue, perennial ryegrass and Kentucky bluegrass. These grasses are commonly used for home lawns, golf course roughs, parks and athletic fields in the Midwest. Although red thread is not lethal, it can cause unsightly bleaching of large areas of a lawn.

What does red thread look like? Red thread is often misdiagnosed as pink patch, another turf disease that develops under similar environmental conditions. Both diseases cause tan, pink, or red circular patches ranging in size from a few inches to two feet in diameter. In addition, both diseases are noted for the formation of pink to red, spiderweb-like threads along the edges of diseased areas when leaves are wet. Leaf blades affected by both diseases die starting at the tip, becoming a tan, light-gray or bleached-white color. Red thread can be distinguished from pink patch by the presence of thick, red tendrils that protrude from affected leaf blades. These tendrils are the “red threads” that give the disease its name.

Where does red thread come from? The fungus, Laetisaria fuciformis, causes red thread.   The fungus grows from the red, thread-like structures (called sclerotia) that survive the winter in infected grass blades, thatch and soil. Sclerotia and infested leaf blades can be moved by water, wind and mowing equipment to other locations where they can cause new infections. Red thread most often develops in wet, cool (59 to 77°F) weather in the spring and fall. The disease is most severe on fine fescues (although other turfgrass species also can be affected) that are growing slowly due to cool weather or inadequate fertilization.

How do I save turf with red thread? Red thread is a cosmetic disease that does not affect either the crown or roots of infected plants. Thus, turf with red thread typically recovers after environmental conditions favorable for growth return and conditions favorable for disease development have passed.

If you use susceptible grass species (e.g., fine fescues and perennial ryegrass), be sure fertilize your lawn optimally in the fall and spring to maintain its growth and vigor. See University of Wisconsin-Extension Bulletin A3435 “Lawn Maintenance” (available at http://learningstore.uwex.edu) for recommendations on routine lawn fertilization. On lawns with a history of red thread, apply nitrogen fertilizer in mid to late spring to reduce disease severity and promote healthy turf. Under dry conditions, water your lawn between midnight to 6 am when dew naturally forms, thus reducing the length of time that your lawn remains wet. Red thread often develops when turfgrass is watered frequently, so DO NOT water your lawn unless you observe wilting.

Fungicide use is not generally recommended for control of red thread due to the cosmetic nature of the disease, the fact that infected turfgrass typically quickly recovers from the disease and the cost of chemical control. However, if you feel that fungicide treatments are needed, products containing strobilurins (e.g., azoxystorbin, trifloxystrobin and fluoxastrobin), as well as flutolanil are currently labeled in Wisconsin for managing red thread and can be very effective when applied before symptoms appear. When using fungicides, DO NOT apply the same active ingredient for all treatments. Instead, alternate the use of at least two ingredients with different modes of action (i.e., DO NOT only use strobilurins) to help minimize problems with fungicide-resistant strains of the red thread fungus. Be sure to read and follow all label instructions of the fungicides that you select to ensure that you use the fungicides in the safest and most effective manner possible.

For more information on red thread: Contact your county Extension agent.

 

What is Microdochium patch? Microdochium patch, also known as pink snow mold, is a fungal disease affecting cool season grasses such as annual, Kentucky, and rough bluegrass; colonial, velvet, and creeping bentgrass; perennial ryegrass; and fine and tall fescue. These grasses are used in the majority of home lawns and golf courses in the Midwest.

What does Microdochium patch look like? Microdochium patch is characterized by the formation of circular patches of dead turf. The dead areas can range in size from a few inches to a few feet in diameter. When Microdochium patch develops on short-cut turf under a layer of snow, distinct dead patches appear that are bleached and matted. When the disease develops on short-cut turf in the absence of snow, dead patches appear reddish-brown. White fungal threads (called a mycelium) typically develop in the center of the patches, with pinkish-red threads forming at the borders. On taller grass (greater than six inches), yellow blighted patches with diffuse margins can form.

Where does Microdochium patch come from? Microdochium patch is caused by the fungus Microdochium nivale which survives as fungal threads or spores in infested plant debris. The fungus begins to grow under the snow during the winter and continues to grow until the turf warms and dries in the spring. In addition, Microdochium patch can be found during damp, cool spring and fall weather. The disease is more severe under cool (30 to 60°F), wet conditions, in alkaline soils, and when high levels of nitrogen fertilizer are applied early (or extremely late) in the growing season.

How do I save turf with Microdochium patch? Turf with Microdochium patch will often recover, but severely affected areas will need to be reseeded or replaced with Microdochium patch-resistant turf. The least susceptible grass species are Kentucky bluegrass and fine fescue.

How do I avoid problems with Microdochium patch in the future? When establishing a lawn, make sure that soils are well-drained and do not accumulate excessive amounts of water. Make sure that the soil pH is 7.0 or below, and also be sure to plant a Microdocium patch resistant grass variety (e.g., Kentucky bluegrass or fine fescue). In established lawns, DO NOT apply fast releasing nitrogen fertilizers (e.g., urea or ammonium nitrate) in the fall, and continue to mow grass until it goes dormant. Maintain a soil pH of 7.0 or below. Remove thatch in your lawn in either September or May, if the thatch layer is greater than ¹/2 inch. Building a snow fence to minimize snow accumulation, and encourage rapid snow melting may also help reduce the incidence and severity of Microdochium patch. Fungicides containing the active ingredients azoxystrobin, chlorothalonil, fenarimol, fludioxonil, iprodione, mancozeb, myclobutanil, PCNB, polyoxin D, propiconazole, pyraclostrobin, thiophanate-methyl, thiram, triadimefon, trifloxystrobin, and vinclozolin are labeled for Microdochium patch control, and can be applied in October or November to prevent disease in the spring. However, these treatments are often not cost-effective. If you decide to use fungicides for control, be sure to read and follow all label instructions of the fungicide that you select to ensure that you use the fungicide in the safest and most effective manner possible.

For more information on Microdochium patch: See UW-Extension bulletins A3187 and A3187-SUPL, or contact your county Extension agent.

Snow Molds
(Microdochium nivale and Typhula spp.)

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

Hosts: 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.

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Necrotic Ring Spot
(Ophiosphaerella korrae)

Occurrence: Spring, summer and fall

Favorable Conditions: Cool (soil temperatures of 55 to 65^oF) and wet conditions for infection, followed by heat and drought stress for symptom development; most severe when soil compaction limits rooting

Host: 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.  

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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.

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Summer Patch

(Magnaporthe poae)

Occurrence: Summer

Favorable conditions: Hot, moist conditions; alkaline (i.e., high) soil and thatch pH

Hosts: 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.

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Dollar Spot

(Sclerotinia homoeocarpa)

Occurrence: Summer

Favorable conditions: High humidity; low nitrogen fertility

Hosts: 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.

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Red Thread

(Laetisaria fuciformis)

Occurrence: Spring through fall

Favorable conditions: Wet, cool conditions

Hosts: 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.

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Rust

(Puccinia spp., Uromyces spp.)

Occurrence: Summer and fall

Favorable conditions: High humidity, low soil moisture, low nitrogen fertility, shade

Hosts: 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.

For more information on lawn diseases: See University of Wisconsin Garden Facts XHT1145, and XHT1150 (available at http://hort.uwex.edu), UW-Extension Bulletin A3187 (available at http://learningstore.uwex.edu), contact the UW-Madison Turfgrass Diagnostic Lab (see http://tdl.wisc.edu) or contact your county Extension agent.

What are Helminthosporium turf diseases?  Helminthosporium diseases of turf are a group of common, cool season turfgrass diseases (including Helminthosporium leaf spot and melting out) that occur throughout North America.  In residential settings, these diseases can severely reduce the aesthetic appeal of a lawn and can lead to expensive lawn replacements.

What do Helminthosporium turf diseases look like?  Symptoms of Helminthosporium turf diseases vary, depending upon the specific pathogen, grass species, weather conditions, and cultural conditions involved.  In general, the diseases lead to patches of thin, dead grass.  On Kentucky bluegrass, and fine and tall fescues, initial symptoms are small, dark purple to black spots on the leaf blades.  Older leaf spots on these hosts are often described as “eyespots” (i.e., round to oval spots with buff-colored centers surrounded by dark brown to dark purple margins).  Infected bentgrasses often initially have a smoky-blue, water-soaked and matted appearance.  As the disease progresses, infected leaves yellow and eventually die.
 
Where do Helminthosporium turf diseases come from?  Helminthosporium turf diseases are caused by several fungi, all of which were at one time lumped within the fungal genus Helminthosporium.  More recently, these fungi have been reclassified into the genera Bipolaris, Drechslera, and Exserohilum.  These fungi overwinter in infected turfgrass and turfgrass debris (e.g., thatch, grass clippings), and throughout the growing season produce spores that can readily infect leaf blades that have been wet for several hours.  Disease development is favored during periods of high temperature when dry conditions alternate with prolonged stretches of cloudy, moist weather.  

How do I save turf with Helminthosporium turf diseases?  Fungicides containing azoxystrobin, captan, chlorothalonil, fludioxonil, fluoxastrobin, iprodione, maneb, mancozeb, myclobutanil, PCNB, polyoxin D, propiconazole, pyraclostrobin, thiophanate-methyl, trifloxystrobin, thiram and vinclozolin are labeled for control of Helminthosporium turf diseases. 

These fungicides will not cure existing infections, but if they are applied early in disease development, may help prevent substantial losses.  If you decide to use fungicides for control, be sure to read and follow all label instructions of the fungicide that you select to ensure that you use the fungicide in the safest and most effective manner possible.  

How do I avoid problems with Helminthosporium turf diseases in the future?  Water, fertilize and mow your lawn properly (see UW-Extension bulletin A3435 for details) to keep it healthy, and growing vigorously.  Turf requires approximately one inch of water per week from natural rain, supplemental irrigation or a combination of both.  If you must irrigate, make sure to water deeply, but infrequently to avoid drought.  Avoid late afternoon and evening watering that can promote longer periods of moisture on leaves.  DO NOT overfertilize.  In particular, avoid heavy applications of nitrogen (especially fast-releasing forms of nitrogen such as urea), particularly during wet weather.  Test leaf tissue from your turf routinely to make sure that the nitrogen to potassium ratio (N:K) is approximately 1:2, and fertilize appropriately to maintain this ratio.  Keep your lawn mowed to between 2½ and 3½ inches, and never remove more than ⅓ of the existing growth when mowing.  Keep the blade on your mower sharp.  Ragged cuts, caused by dull mower blades, provide easier entry points for Helminthosporium turf disease fungi.  Collect and destroy (by composting, burying or burning) lawn clippings from infected plants and try to clean any contaminated clippings from your mower.  Helminthosporium turf disease fungi can survive and can easily be moved from place to place in grass clippings.  If Helminthosporium turf diseases have been a problem in your lawn, consider using a blend of resistant turfgrass cultivars or a mixture of cool-season turfgrasses when establishing a new lawn or over-seeding an existing lawn.  Resistant cultivars of Kentucky bluegrass include ‘Alpine’, ‘America’, ‘Boutique’, ‘Brilliant’, ‘Buckingham’, ‘Freedom II’, ‘Merion’, ‘Moonlight’, ‘Serene’, and ‘Unique’ (see UW-Extension bulletin A3187 for details).

In summary, to avoid problems with Helminthosporium turf diseases:

• Reduce leaf wetness (June to Sept.)
• Avoid drought stress (July, Aug.)
• Avoid excess N (May to Aug)
• Balance fertility (N:K = 1:2) (Spring, Fall)
• Mow at 2½ to 3½ in. (May to Nov.)
• Keep mower blades sharp (May to Nov.)
• Avoid mowing wet grass (May to Nov.)
• Collect diseased clippings (Spring)
• Plant resistant turf cultivars (Fall)
• Follow fungicide label (Always)

For more information on Helminthosporium turf diseases:  See UW-Extension Bulletin A3187 or contact your county Extension agent.