Category Archives: Turf

Turf

Typhula Blight

November 12, 2019 ddlang

UW Plant Disease Facts

Authors: Paul Koch, UW-Plant Pathology and PJ Liesch, UW Insect Diagnostic Lab

Last Revised: 03/01/2024

D-number: D0119

Typhula blight causes circular patches of bleached turf that often merge to form larger, irregularly-shaped bleached areas.

What is Typhula blight?

Typhula blight, also known as gray or speckled snow mold, is a fungal disease affecting all cool season turf grasses (e.g., Kentucky bluegrass, creeping bentgrass, tall fescue, fine fescue, perennial ryegrass) grown in areas with prolonged snow cover. These grasses are widely used in residential lawns and golf courses in Wisconsin and elsewhere in the Midwest.

What does Typhula blight look like?

Typhula blight initially appears as roughly circular patches of bleached or straw-colored turf that can be up to two to three feet in diameter. When the disease is severe, patches can merge to form larger, irregularly-shaped bleached areas. Affected turf is often matted and can have a water-soaked appearance. At the edges of patches, masses of grayish-white fungal threads (called a mycelium) may form. In addition, tiny (¹/₆₄ to ³/₁₆ inch diameter) reddish-brown or black fungal survival structures (called sclerotia) may be present. Typhula blight looks very similar to Microdochium patch/pink snow mold (see UW Plant Disease Facts D0073, Microdochium Patch), but the Microdochium patch fungus does not produce sclerotia.

Where does Typhula blight come from?

Typhula blight is caused by two closely related fungi Typhula incarnata and Typhula ishikariensis. In general, T. incarnata is more common in the southern half of Wisconsin while T. ishikariensis is more common in the northern half of the state. To distinguish between the two Typhula species, look for sclerotia. Sclerotia of T. incarnata are reddish-brown and ¹/₁₆ to ³/₁₆ inch in diameter. Sclerotia of T. ishikariensis are black and ¹/₆₄ to ¹/₁₆ inch in diameter, resembling flakes of pepper. Typhula blight develops when there is a prolonged period (more than 60 days) when snow covers unfrozen ground and soil temperatures are just above freezing (30 to 40˚F). Typhula blight typically does not develop if the ground freezes before the first snowfall in the fall/winter, or if snow melts during the middle of winter exposing the ground to colder temperatures. Damage from Typhula blight is usually not noticed until snow melts in spring. Applying high nitrogen fertilizers in the fall can increase the risk of Typhula blight developing over the winter.

Sclerotia (survival structures) of Typhula incarnata are small and red or rust-colored.

How do I save a turf with Typhula blight?

Turf with Typhula blight may or may not recover depending on the fungus involved. Both T. incarnata and T. ishikariensis can infect and kill turf leaves, but only T. ishikariensis kills the plant crown. Turf infected with T. incarnata typically recovers quickly once normal turf growth resumes in the spring. Turf infected by T. ishikariensis often suffers from crown injury and death, making it less likely to recover and more likely to require replanting in spring. Lightly raking infected turf and reseeding in spring can help speed turf recovery.

How do I avoid problems with Typhula blight in the future?

Consider planting less-susceptible turfgrass species (e.g., fine fescues) to limit the impact of Typhula blight. Also, avoid using fast-release fertilizers in late fall that can predispose turf to Typhula infections. Finally, continue to mow turf until it goes dormant as this will help prevent excessive turf top growth that is more easily infected by Typhula.

Because turf often recovers naturally from Typhula blight, fungicide treatments are typically NOT warranted for home lawns. However, fungicide treatments may be needed to prevent severe damage when a lawn has a history of the disease and when predictions for the upcoming winter suggest that snow cover will persist on unfrozen ground for longer then three months. Many effective fungicides are available for snow mold control in home lawns and include the active ingredients azoxystrobin, propiconazole, pyraclostrobin, and tebuconazole. For the most up-to-date fungicide recommendations for Typhula blight, please visit the Turf Pest Management Mobile website (https://turfpests.wisc.edu/). Fungicide applications should be made in October or November to prevent disease in the spring. If you decide to use fungicides for control, read and follow all label instructions to ensure that you use the product that you select in the safest and most effective manner possible.

For more information on Typhula blight:

Contact the University of Wisconsin Turf Diagnostic Lab (TDL) at (608) 845-2535 or hockemeyer@wisc.edu.

This Fact Sheet is also available in PDF format:

Full Color PDF

An EEO/Affirmative Action employer, University of Wisconsin-Madison Division of Extension provides equal opportunities in employment and programming, including Title IX and ADA requirements. This document can be provided in an alternative format by calling Brian Hudelson at (608) 262-2863 (711 for Wisconsin Relay).

References to pesticide products in this publication are for your convenience and are not an endorsement or criticism of one product over similar products. You are responsible for using pesticides according to the manufacturer’s current label directions. Follow directions exactly to protect the environment and people from pesticide exposure. Failure to do so violates the law.

Thanks to John Panuska, Carol Shirk, and Doug Soldat for reviewing this document.

A complete inventory of UW Plant Disease Facts is available at the University of Wisconsin-Madison Plant Disease Diagnostics Clinic website: https://pddc.wisc.edu.

Submit additional lawn, landscape, and gardening questions at https://hort.extension.wisc.edu/ask-a-gardening-question/.

Misc, Turf

Fairy Rings

November 8, 2016 dlang6

UW Plant Disease Facts

Authors: Margot Cumming*, UW-Madison Plant Pathology

Last Revised: 02/29/2024

D-number: D0051

Type 1 (top), Type 2 (middle) and Type 3 (bottom) fairy rings.

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 UW Bulletin A3435, Lawn Maintenance (available at https://learningstore.extension.wisc.edu/).

For more information on fairy rings:

Contact the University of Wisconsin Turf Diagnostic Lab (TDL) at (608) 845-2535 or hockemeyer@wisc.edu.

This Fact Sheet is also available in PDF format:

Full Color PDF

* Completed as partial fulfillment of the requirements for Plant Pathology 558 at the University of Wisconsin Madison.

Thanks to Anne Buckelew, Lisa Johnson, Ryan Kelley, Paul Koch, Glennie Mihalovic and Craig Saxe for reviewing this document.

A complete inventory of UW Plant Disease Facts is available at the University of Wisconsin-Madison Plant Disease Diagnostics Clinic website: https://pddc.wisc.edu.

Submit additional lawn, landscape, and gardening questions at https://hort.extension.wisc.edu/ask-a-gardening-question/.

Disease - Field and Forage, Disease - Herbaceous Ornamental, Disease - Vegetable, Turf

Root-Knot Nematode

August 15, 2015 hudelson

UW Plant Disease Facts

Authors: Nolan Bornowski*, UW-Madison Plant Pathology

Last Revised: 03/01/2024

D-number: D0097

Root-knot nematodes (Meloidogyne spp.) are small, soilborne, worm-like organisms that infect many agricultural and horticultural plants. Root-knot nematodes are found worldwide, and are named for the swellings (called “galls” or “knots”) that they cause on plant roots. Economically-important species of Meloidogyne include M. arenaria, M. hapla, M. incognita, and M. javanica. Of these, M. hapla (commonly known as Northern root-knot nematode) is most likely to be found in Wisconsin soils.

Root-knot nematodes cause swollen, distorted roots that can interfere with movement of water and nutrients within a plant.

Appearance:

Root-knot nematodes are about ¹/₁₀ the size of a pinhead and are typically embedded inside roots. They are impossible to see with the naked eye. Juvenile root-knot nematodes (both males and females), as well as adult males, are vermiform (i.e., worm-shaped) and live in the soil. Adult females are spherical in shape and live inside roots. Both males and females possess a thin, tube-like structure called a stylet that they use for penetrating root tissue.

Symptoms and Effects:

When root-knot nematodes enter roots, they release chemicals that cause nearby root cells to enlarge. This leads to the formation of swollen, distorted areas in roots known as galls or knots. The number and size of galls varies depending on plant species and cultivar, and the number of root-knot nematodes in the soil. On some hosts (e.g., grasses) root swelling can be very difficult to detect. Nematode feeding interferes with proper root function (e.g., water and nutrient movement). Thus, infected plants may be stunted and wilted, may exhibit discolorations (e.g., yellowing) typical of plants with nutrient deficiencies, and ultimately (in field or vegetable crops) may have lower yields. Because root-knot nematodes tend not to be uniformly distributed in the soil, symptomatic plants often occur in patches and are typically surrounded by plants of normal height and appearance. Environmental factors such as slope, soil type, or soil moisture can cause similar patchy patterns, so identification of a root-knot nematode problem requires examination of symptomatic plants at a lab qualified to perform nematode diagnostics.

Life Cycle:

Root-knot nematodes (i.e., M. hapla) are native to Wisconsin and can be spread whenever contaminated soil or infected plants are moved. Root-knot nematodes survive the winter as eggs in the soil. Like insects, root-knot nematodes have several juvenile stages and the nematodes molt (i.e., shed their outer layers) as they grow. The second juvenile stage of root-knot nematode is the most important, because at this stage the nematode seeks out and infects plant roots. Once it has entered a root, a root-knot nematode molts three more times before becoming an adult. A male root-knot nematode is able to move about freely and can leave a root. A female root-knot nematode remains and feeds in a given location within a root. Eventually, a female enlarges to the point where a portion of her body extends to the root surface and this allows her to lay her eggs in the soil. In some hosts, eggs can also be found within the galls.

Control:

If you are having a root-knot nematode problem in your garden, consider crop rotation and the use of cover crops as management tools. See University of Wisconsin Garden Facts XHT1210, Crop Rotation in the Home Vegetable Garden and XHT1209, Using Cover Crops and Green Manures in the Home Vegetable Garden for details. If used properly, these techniques can be effective in reducing the number of root-knot nematodes in the soil. M. hapla, the root-knot nematode species most common in Wisconsin, does not infect corn, wheat, oats or rye, so use of these crops in a rotation or as cover crops often provides great benefit.

Cover crops of French marigolds (Tagetes patula) also have been shown to reduce the number of root-knot nematodes in soil. This common garden ornamental releases a chemical (alpha-terthienyl) that is highly toxic to root-knot nematodes and prevents their eggs from hatching. As an added bonus, root-knot nematodes are not able to develop properly in marigold roots. When using crop rotation or cover crops, proper broadleaf weed control is critical because weeds can provide a place for root-knot nematodes to survive and reproduce.

Finally, consider amending the soil in your garden with organic matter such as compost or leaf mulch. Such amendments tend to increase the diversity of microorganisms in the soil and can encourage the growth of certain soilborne fungi that ensnare and feed on root knot nematodes, and parasitize their eggs.

For more information on root-knot nematode:

Contact the University of Wisconsin Plant Disease Diagnostics Clinic (PDDC) at (608) 262-2863 or pddc@wisc.edu.

This Fact Sheet is also available in PDF format:

Full Color PDF

*Completed as partial fulfillment of the requirements for Plant Pathology 558 at the University of Wisconsin Madison.

Thanks to Freddie Bornowski, Ashley Ellinghuysen, Amy Kispert, Ian McCue , Ann MacGuidwin, Scott Reuss and Ken Schroeder for reviewing this document.

A complete inventory of UW Plant Disease Facts is available at the University of Wisconsin-Madison Plant Disease Diagnostics Clinic website: https://pddc.wisc.edu.

Submit additional lawn, landscape, and gardening questions at https://hort.extension.wisc.edu/ask-a-gardening-question/.

Turf

Red Thread

August 14, 2015 hudelson

UW Plant Disease Facts

Authors: Benjamin Van Ryzin*, UW-Madison Plant Pathology

Last Revised: 03/01/2024

D-number: D0092

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.

Bleached grass blades with fuzzy, pink to red masses of spider web-like strands are typical of red thread. (Photo courtesy of R. Latin, Purdue University)

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.

Red thread-like structures, called sclerotia, protrude from leaf blades infected by the red thread fungus. (Photo courtesy of Paul Koch)

How do I avoid problems with red thread in the future?

When seeding or sodding a lawn, choose grasses that are less susceptible to red thread (e.g., Kentucky bluegrass and hard fescue). 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 UW Bulletin A3435, Lawn Maintenance (available at https://learningstore.extension.wisc.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 the University of Wisconsin Turf Diagnostic Lab (TDL) at (608) 845-2535 or hockemeyer@wisc.edu.

This Fact Sheet is also available in PDF format:

Full Color PDF

*Completed as partial fulfillment of the requirements for Plant Pathology 558 at the University of Wisconsin Madison.

Thanks to Paul Koch, P. J. Liesch, Doug Soldat, Gary Van Ryzin and Pamela Van Ryzin for reviewing this document.

A complete inventory of UW Plant Disease Facts is available at the University of Wisconsin-Madison Plant Disease Diagnostics Clinic website: https://pddc.wisc.edu.

Submit additional lawn, landscape, and gardening questions at https://hort.extension.wisc.edu/ask-a-gardening-question/.

Turf

Microdochium Patch

July 29, 2015 hudelson

UW Plant Disease Facts

Authors: Sarah Rosenthal*, UW-Plant Breeding and Plant Genetics and Geunhwa Jung, formerly of UW-Plant Pathology

Last Revised: 03/01/2024

D-number: D0073

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.

On short-cut grass, Microdochium patch leads to the formation of round, pink-edged patches of dead turf that form over the winter.

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.

On taller grass, Microdochium patch can lead to a diffuse, yellow blighting of the turf.

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 encouraging 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 product in the safest and most effective manner possible.

For more information on Microdochium patch:

Contact the University of Wisconsin Turf Diagnostic Lab (TDL) at (608) 845-2535 or hockemeyer@wisc.edu.

This Fact Sheet is also available in PDF format:

Full Color PDF

*Completed as partial fulfillment of the requirements for Plant Pathology 559 – Diseases of Economic Plants at the University of Wisconsin Madison.

Thanks to Jason Dettman-Kruse, Bruce Schweiger and John Stier for reviewing this document.

A complete inventory of UW Plant Disease Facts is available at the University of Wisconsin-Madison Plant Disease Diagnostics Clinic website: https://pddc.wisc.edu.

Submit additional lawn, landscape, and gardening questions at https://hort.extension.wisc.edu/ask-a-gardening-question/.

Quick Reference Guide, Turf

Lawn Disease Quick Reference

July 28, 2015 hudelson

UW Plant Disease Facts

Authors: P.J. Liesch, UW-Madison Plant Pathology; Vijai Pandian, UW-Extension Brown County; and Jim Kerns, formerly of UW-Madison Plant Pathology

Last Revised: 03/01/2024

D-number: D0069

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.

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.

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.

Summer Patch
(Magnaporthiopsis 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.

Dollar Spot
(Clarireedia jacksonii)

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.

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.

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:

Contact the University of Wisconsin Turf Diagnostic Lab (TDL) at (608) 845-2535 or hockemeyer@wisc.edu.

This Fact Sheet is also available in PDF format:

Full Color PDF

Thanks to Diana Alfuth, Doug Soldat and Karen Schleis for reviewing this document.

A complete inventory of UW Plant Disease Facts is available at the University of Wisconsin-Madison Plant Disease Diagnostics Clinic website: https://pddc.wisc.edu.

Submit additional lawn, landscape, and gardening questions at https://hort.extension.wisc.edu/ask-a-gardening-question/.

Turf

Helminthosporium Turf Diseases

July 24, 2015 hudelson

UW Plant Disease Facts

Authors: Hye Sook Kim* and Brian Hudelson, UW-Plant Pathology Geunhwa Jung, University of Massachusetts Amherst-Plant, Soil and Insect Sciences

Last Revised: 03/01/2024

D-number: D0059

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.

Helminthosporium turf diseases cause “eyespots”, round to oval spots with buff-colored centers surrounded by dark brown to dark purple margins.

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, they 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.

Helminthosporium turf diseases cause dead patches on intensively managed creeping bentgrass.

How do I avoid problems with Helminthosporium turf diseases in the future?

Water, fertilize and mow your lawn properly to keep it healthy, and growing vigorously. See UW Bulletin A3435, Lawn Maintenance (available at https://learningstore.extension.wisc.edu/) for details. 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 Bulletin A3187, Turf Diseases of the Great Lakes Region (available at https://learningstore.extension.wisc.edu/), 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:

Contact the University of Wisconsin Turf Diagnostic Lab (TDL) at (608) 845-2535 or hockemeyer@wisc.edu.

This Fact Sheet is also available in PDF format:

Full Color PDF

*Completed as partial fulfillment of the requirements for the graduate course: “Plant Pathology 559: Diseases of Economic Crops.”

Thanks to Diana Alfuth, Judy Reith-Rozelle and Deb Simons for reviewing this document.

A complete inventory of UW Plant Disease Facts is available at the University of Wisconsin-Madison Plant Disease Diagnostics Clinic website: https://pddc.wisc.edu.

Submit additional lawn, landscape, and gardening questions at https://hort.extension.wisc.edu/ask-a-gardening-question/.

Disease - Broad Leafed Woody Ornamental, Disease - Field and Forage, Disease - Fruit Crop, Disease - Herbaceous Ornamental, Disease - Needled Woody Ornamental, Disease - Vegetable, Misc, Turf

Dodder

July 21, 2015 hudelson

UW Plant Disease Facts

Authors: Jennifer Clifford, Amilcar Sanchez, Trenton Stanger, and Brian Hudelson UW-Madison Plant Pathology

Last Revised: 02/29/2024

D-number: D0129

Spaghetti-like dodder plants parasitizing carrots.

What is dodder?

Dodder is the name of several species of parasitic plants that are widely distributed in North America and Europe. Plants parasitized by dodder include alfalfa, carrots, onions, potatoes, cranberries, a variety of herbaceous and woody ornamentals, and many weed species. Parasitized plants become weakened, have reduced yields (in the case of agronomic crops), and can potentially die.

What does dodder look like?

Dodders lack roots and leaves, and also lack chlorophyll, the green pigment found in most plants. Dodders have slender, yellow-orange stems that cover infected plants in a spreading, tangled, spaghetti-like mass. From May through July, dodders produce white, pink, or yellowish flowers.

Where does dodder come from?

Dodders produce large numbers of seeds that germinate in the spring to produce shoots that attach to suitable host plants. Dodders penetrate host tissue, and absorb nutrients via specialized structures called haustoria. Once established on a host, the bottom of a dodder plant dies (thereby severing its connection with the soil), and the dodder plant becomes dependent on the host plant for water and nutrients.

How do I save plants parasitized by dodder?

On woody ornamentals, simply prune out dodder-parasitized branches. When small patches of dodder occur among herbaceous plants, apply contact herbicides such as 2,4-D early in the season, preferably before dodder seedlings have parasitized host plants. Keep in mind that use of contact herbicides will likely also kill host plants. Alternatively, cut or burn dodder and parasitized plants to keep dodder from spreading, and to prevent seed production. For widespread dodder infestations, a combination of frequent tilling, burning and herbicide applications may be needed to achieve control. Be sure to read and follow all label instructions of the herbicide that you select to ensure that you use the product in the safest and most effective manner possible.

How do I avoid problems with dodder in the future?

Dodder’s wide host range and ability to survive as dormant seeds in soil make eradication difficult. Preventing introduction of dodder is the best method of control. Use dodder-free seed, and be sure to clean equipment thoroughly after working in a dodder-infested area. Try to restrict animal movement between infested and non-infested areas as well. Depending upon the specific crop or location, use of pre-emergent herbicides containing DCPA, dichlobenil, propyzamide, or trifluralin may be possible to prevent germination of dodder seeds. Destroy actively growing dodder and any parasitized plants before the dodder produces seeds. In agricultural settings where dodder has been a problem, rotate away from susceptible crops and grow non-host crops (e.g., corn, soybeans, or small grain cereals). In conjunction with rotation, adequate control of weed hosts is critical to achieve control.

For more information on dodder:

Contact the University of Wisconsin Plant Disease Diagnostics Clinic (PDDC) at (608) 262-2863 or pddc@wisc.edu.

This Fact Sheet is also available in PDF format:

Full Color PDF

Thanks to Lis Friemoth, Matt Lippert and Dan O’Neil for reviewing this document.

A complete inventory of UW Plant Disease Facts is available at the University of Wisconsin-Madison Plant Disease Diagnostics Clinic website: https://pddc.wisc.edu.

Submit additional lawn, landscape, and gardening questions at https://hort.extension.wisc.edu/ask-a-gardening-question/.