Diseases
Anthracnose Foliar Blight and Basal Rot
(Colletotrichum graminicola)  
Symptoms and signs:
Anthracnose foliar blight appears as irregular yellow or bronze patches of diseased turf. Symptoms on individual plants first appear as yellow or red lesions on the oldest (outermost) leaves, then progress to a blighting of younger leaves and shoots. Occasionally, fungal fruiting structures called acervuli can be observed with a good quality hand lens on diseased leaves and stems. Acervuli resemble small, black pin cushions and are the location of spore production.Anthracnose basal rot symptoms vary depending on the grass species affected. On annual bluegrass, symptoms appear as a bright yellowing of the turf in irregular patches. Affected bentgrass turf typically appears as irregular red or bronze patches are rarely appears yellow. On individual plants affected with anthracnose basal rot, a dark brown or black color is present at the base of the plant. As the disease worsens, the darkening (rotting) progresses up the stem and acervuli can be observed with a hand lens on stem and leaf tissue.
Disease Cycle:
The causal fungus, Colletotrichum graminicola, survives the winter as dormant resting structures called sclerotia and as dormant mycelium in infected plant debris. During early spring outbreaks of anthracnose basal rot, the fungus, which may have overwintered in the plant, initiates infection at the base of the plant. Outbreaks of anthracnose foliar blight and / or basal rot can result when spores produced in acervuli are dispersed by splashing water or tracked by mowing equipment from one area to another. These spores then germinate and cause new infections on other plants. Anthracnose is likely to occur when plants are growing slowly (during periods of hot and cold temperatures), during overcast periods, and in high humidity conditions.
Cultural Control:
Proper fetilization and maintaining good soil physical conditions are the most effective approaches to managing anthracnose. If your turf is underfertilized, increase the rate and / or frequency of nitrogen fertilizer applications. This will improve resistance to the disease and sid in turf recovery. Add potassium and phosphorus if your soil test report indicates a need. Improved drainage and a regular aeration program will reduce excess soil moisture, alleviate compaction, and improve root growth, creating conditions that are less favorable for anthracnose.
Chemical Control:
Fungicides are only used to control anthracnose on golf courses. Preventative (before the disease occurs) applications of fungicides are generally more effective in controlling anthracnose foliar blight and basal rot than curative (after the disease appears) applications. Application timing will vary from one region to another and possibly from year to year at the same location. The best way to time your applications is to keep records for several seasons of the environmental conditions under which the disease occurred on your course, then apply fungicides when conditions are conducive for disease development. |
Brown Patch
(Rhizoctonia solani) 
Symptoms and signs:
Brown patch is a major summer disease of lawns and golf courses. The most susceptible grass species include perennial ryegrass, tall fescue, and the bentgrasses. Occasionally, brown patch becomes a problem on Kentucky bluegrasses in mid- to late-summer during extended periods of high temperature and humidity.On high-cut turf, patches may be up to several meters in diameter and circular. In early morning on dew-covered turf, white mycelium of the causal fungus can often be seen on and between grass leaves and stems in the patch. Sometimes, all the grass within the patch is killed, creating a sunken or "pocket" effect. More often, the turf in these patches is thinned rather than completely killed. Occasionally, no circular pattern can be seen, and disease appears as a diffuse blight. On tall fescue, symptoms of brown patch can be observed on individual leaves and not necessarily in patches. Symptoms on leaves appear as irregular tan or light brown lesions surrounded by dark brown borders. In severe cases, the entire stand may look discolored and thinned. A distinguishing feature of brown patch on golf course putting greens is the presence of dark purplish rings around the periphery of the patches. These are called smoke rings and range from 6-13mm wide. Smoke rings are more pronounced in the early morning hours, usually fading by midday.
Disease Cycle:
The causal fungus overwinters in the form of resting bodies called sclerotia, either within infected grass tissue or in the soil. The fungus is capable of surviving in soil for years in the absence of a susceptible grass. Disease activity is prevalent when surface moisture and humidity are high, night temperatures are above 20°C and daytime temperatures average 27° C or above. Rainy weather and a saturated atmosphere (100 percent relative humidity) greatly speed disease development. Disease severity is greater on lush, succulent turfgrass maintained with high nitrogen levels than on grass maintained with moderate levels.
Cultural Control:
Applying nitrogen fertilizers on turf with a known history of brown patch during hot and humid weather may create the need for fungicide applications to control the disease. Removal of dew or guttation water that collects on the grass leaves each morning has proven effective as an aid in reducing brown patch. This removal can be achieved by mowing or by dragging a water hose across the area. Necesary watering should be done in time for the grass to dry before nightfall.
Chemical Control:
Fungicide treatment should only be needed on high-value ryegreass or bentgrass turfs. Fungicide treatment usually is made on a curative basis; the first spray should be applied immediately after the onset of symptoms, especially if prolonged hot, humid weather is expected. In areas where brown patch causes severe thinning on putting greens, preventative fungicide applications may be justified. |
Damping-off Diseases
(Pythium, Rhizoctonia, and Fusarium spp.) 
Symptoms and signs:
Damping-off diseases occur as seed rots and blights of seedlings. This disease seldom occurs on grass planted in early fall or early spring. However, in seedings from May to August, especially if hot, wet weather persists, seed may decay prior to germination, or new seedlings may become diseased and die.Seedlings become blighted, then collapse and die, forming circular or irregular patches. Affected plants often appear water soaked and slimy. Sometimes mycelium can be seen on dew-covered grass in early morning. The dead tissue may mat together somewhat like paper-mache and form a crust over the soil surface.
Disease Cycle:
Most soils contain fungi that can attack seeds and seedlings. When conditions are favorable for grass seed germination and growth, as in the early fall and spring, these organisms usually are of little significance. Warm, wet weather, however, is more favorable for damping-off fungi and less favorable for seedlings. Under these conditions, fungi can severely damage seed and seedlings.Damping-off outbreaks are triggered by high temperatures and humidity, water-logged soils, excessive fertilizer, or an excessive seeding rate. In warm weather, higher-than-normal rates of seed may produce a very dense stand of seedlings that will hinder the escape of moisture from the soil surface. Such wet conditions over long periods of time are ideal for invasion by damping-off fungi. High rates of fertilizer can produce a succulent turf that is more susceptible to attack by damping-off fungi. With new seeding techniques, such as hydroseeding and hydromulching, seeding is done all year round, and as a result, damping-off has become a more frequent cause of stand failure. Stand loss to seed decay or seedling blight makes successive attempts to reseed the dead areas more difficult.
Cultural Control:
Cultural control of damping-off diseases is based on providing favorable conditions for germination of the grass seeds and growth of the plants while minimizing the conditions that favor the fungi. Often, this can be accomplished by planting in spring or fall when temperatures are cool and grass grows well. For summer seedings, prepare a good seed bed, select a seeding rate sufficiently low so that the stand is not too dense, do not apply excessive amounts of fertilizer, and prevent free water from standing on the soil surface. Avoid using excessive quantities of mulch following seeding.
Chemical Control:
Three types of chemical control methods may be used with new turf seedings: fungicide seed treatment prior to seeding, fungicide drenches or sprays on the soil after seeding, and/or fungicide sprays on the young seedlings. Each method can be effective, and the choice offers the possibility of chemical protection at various intervals during turf establishment. Selection of fungicide control practices depend on the site, the type of grass seeded, the seeding rate, and the environment at establishment. |
Dollar Spot
(Sclerotinia homoeocarpa) 
Symptoms and signs:
With regular watering of home lawns throughout much of the growing season, many turfgrass diseases, once problems only on golf courses and recreational turf areas, now appear commonly. Perhaps the most important of these is dollar spot.On golf course greens cut at or below 5mm, this disease appears as white or tan spots of dead turf about the size of a silver dollar. Hence the name dollar spot. On home lawns cut at 25-75mm, dead areas may reach 50-100mm in diameter. These spots may run together, producing large areas of dead turf. Affected leaves initially show yellow-green blotches, which progress to a light straw color with a reddish-brown margin. Occasionally, white mycelium can be seen covering affected leaves in early morning on dew-covered grass. Dollar spot symptoms occur anytime from early to late summer. The disease usually reaches peak activity when air temperatures are in the 27° C range and under high humidity. Symptoms also may appear in the fall. The most severe cases of dollar spot occur on turf receiving closely-spaced summer irrigation. The disease may also occur on nonirrigated turf when humidity is high from prolonged muggy summer weather. Dollar spot is more severe under nitrogen deficiency or when grass grows slowly.
Disease Cycle:
The causal fungus spreads via mycelium on infected plant parts (mostly clippings). Mycelium may be carried by the wind, water, or on turf equipment and shoes. This fungus does not produce spores. Sclerotinia homoeocarpa is thought to survive as thick-walled crusts of mycelium called pseudosclerotia in dormant infected plant tissues.
Cultural Control:
Late spring nitrogen-fertilizer applications can help to minimize dollar spot severity, since growth will be stimulated during the period (early summer) when dollar spot infection begins. On lawns, fertilizer that releases nitrogen slowly over an extended period is more advantageous than a quick-release product at this time of year. On golf courses, quick-release nitrogen fertilizers can be applied frequently at very light rates instead of using a slow-release fertilizer. Irrigate deeply, infrequently, and early in the morning to minimize moisture accumulation on leaves. Also, remove dew by early morning mowing or by dragging the turf with a water hose.
Chemical Control:
On irrigated turf with persistent dollar spot problems, fungicides are very effective against most forms of the causal fungus. Fungicides are almost always applied on a curative basis for controlling dollar spot. Both contact and systemic fungicides are effective in controlling this disease. Because resistance to certain systemic fungicides has occurred with Sclerotinia homoeocarpa, using contact fungicides in a control program is suggested. |
Fairy Ring
(Various Basidiomycetes) 
Symptoms and signs:
Fairy rings typically appear as rings of dark green and fast-growing turf. They may also appear as rings of slow-growing or killed turf. The bands of affected turf are from 100-300mm in width, forming more or less continuous rings ranging from 1-60m across. In some instances, the center of a stimulated band may contain weakened or dead grass, or bands may have an inner zone of stimulated grass edged with dead or stunted turf on either side.The first visible evidence of a new fairy ring is usually a cluster of mushrooms or toadstools. They usually appear at the outer edge of rings in late summer or early fall, during periods of high soil moisture.
Disease Cycle:
Fairy rings are produced by colonies of mushroom fungi that live in soil and thatch. These colonies obtain food from decaying organic matter and grow outward radially, increasing in size year after year. The ring of stimulated grass is thought to be caused by nitrogen substances produced by the breakdown of organic matter by the fungi. The fungi usually do not attack grass, but sometimes they repel water, resulting in death of the turf due to drought. The causal fungi are spread when fungal threads, bits of mushrooms, or spores from the mushrooms are introduced into soil under a turf area.
Cultural Control:
Try to maintain a sufficient growth rate of the grass. Mow frequently to minimize the differences in grass vigor between the ring and the rest of the lawn. At times, large areas may be killed by fairy rings. When the grass is killed, it may be possible to remove the sod and the top 150mm of soil and then reseed or resod. However, this practice does not always work. Sometimes nothing, not even weeds, will grow in areas killed by fairy rings.
Chemical Control:
Attempts to control fairy rings with fungicide drenches or soil fumigation have met with little or no success. |
Fusarium Patch
(Microdochium nivale) 
Symptoms and signs:
Fusarium patch are diseases caused by the fungus Microdochium nivale. The causal organism of these diseases, Microdochium nivale, was formerly known as Fusarium nivale. To avoid confusion, Fusarium was retained as the disease name.Pink snow mold is a true snow mold since it develops under snow cover. The disease gets its name from the accumulation of pink fungal spores that pile up on the leaves of infected grass plants, producing a pink cast on circular patches of matted grass. Usually only leaves are attacked, but under conditions favorable for disease development the fungus may kill the crowns and roots as well. Thus, pink snow mold can be more severe than gray snow mold. Fusarium patch is similar in appearance to pink snow mold except that the centers of the patches are not usually as matted. Often, a fluffy growth of mycelium can be observed around the periphery of the patch. During periods of cool, wet weather from October to April, Fusarium patch may appear when temperatures are in the 5° to 10° C range. If pink snow mold develops in the cold, wet weather in early fall, the fungus may continue its activity through the winter and into spring. Damage to the turf is then likely to be quite severe and long-lasting.
Disease Cycle:
The fungus survives warm dry weather as dormant fungal mycelium or as dormant spores in soil and thatch. Spores germinate in cool, wet conditions, producing hyphae that infect grass leaves.
Cultural Control:
Fusarium Patch mold usually can be managed successfully in home lawns without fungicides provided the lawn has been established for more than a year. Mow on a regular schedule well into the fall, and avoid high unclipped grass that tends to fall over and mat under snow cover. Try to avoid creating snow banks when removing and piling snow from sidewalks and driveways. Straw mulches and piles of leaves provide a favorable environment for pink snow mold and should be removed from the lawn before snow fall. In general, creeping bentgrass and perennial ryegrass are most susceptible to this disease, whereas Kentucky bluegrass and the fine fescues are only moderately susceptible.Fusarium patch is typically only a problem on golf courses and can be managed by maintaining a balanced fertility program and avoiding excessive nitrogen applications in mid-fall.
Chemical Control:
Fungicide treatment may be needed to control pink snow mold and Fusarium patch in new turfgrass seedings or if a history of unmanageable outbreaks is known. On golf courses, fall or spring fungicide applications may be needed in cold, wet weather. |
Leaf Spot and Melting-out Diseases
(Bipolaris, Drechslera, and Exserohilum spp.)
Symptoms and signs:
Leaf spot and melting-out diseases are incited by a group of fungi in the genera Bipolaris, Drechslera, and Exserohilum. These fungi used to be referred to as Helminthosporium and many individuals still use this name for convenience. Every cool-season grass species probably has a leaf spot/melting-out disease associated with it, but Kentucky bluegrass is particularly susceptible. These organisms, under pasture and native grassland conditions, cause leaf spots of little consequence. However, as cutting height is reduced and the nitrogen level increased, leaf spot diseases may become so severe that complete loss of the turf can occur.The causal fungi usually first invade the leaves, producing small brown spots. As the disease worsens, the spots on leaf blades expand and produce a dark purplish-red oval border around a tan center. The spots enlarge until the entire width of the leaf blade is blighted. The leaf-spotting or leaf-blighting phase is less damaging to the turfgrass than is the melting-out (crown and root-rot) phase of the diseases. In melting-out, the crowns and roots are damaged, causing severe thinning of the turf.
Disease Cycle:
This disease cycle outlines the most problematic leaf spot disease, spring leaf spot/melting-out of Kentucky bluegrasses. The causal fungus survives the winter in crowns and roots of turfgrass or on turf debris on or in the soil. The fungus becomes active during the cool, wet weather of spring. Spores are produced by the causal fungus on leaves and are released and splashed by rain or irrigation water to newly-emerging grass leaves, causing new leaf spots. Successive generations of spores and leaf spots are produced during mid- to late-spring. Spores wash to the crown and root areas, inciting the melting-out phase of the disease usually by late spring or early summer.Keep in mind that not all leaf spot diseases are spring problems. During summer, leaf spotting fungi can attack nearly every grass species. Certain varieties of Kentucky bluegrass, perennial ryegrass, bentgrasses, tall fescue, and fine fescues are susceptible. It is very difficult to predict when the symptoms will be most severe. In most Kentucky bluegrass turfs, however, mid- to late-spring is the time of greatest activity and damage.
Cultural Control:
Applying excessive nitrogen in early spring usually will make leaf spot and melting-out diseases more severe. These diseases can also be severe under nitrogen deficiencies. The lush, dark green, fast growing lawn in early-spring is the kind of condition that encourages the disease in May. Probably the most important factor in controlling spring leaf spot and melting-out diseases is not to apply excessive nitrogen fertilizer (more than 500g nitrogen/100m²) in early spring. A nitrogen application in the range of 200-400g nitrogen/100m² in early spring is a reasonable amount of fertilizer to apply for most Kentucky bluegrass lawns. Possibly the best nonchemical method for controlling leaf spot and melting-out diseases is to replant damaged and disease-prone areas with resistant varieties.
Chemical Control:
Fungicides effectively control leaf spot and melting-out diseases, but correct application and timing are critical. An effective fungicide program requires that the first application be made in early April when the grass begins to green and that applications be repeated during late April and early May, usually at two-week intervals. Fungicides applied at the melting-out stage, when the damage is readily apparent, usually produce little improvement. Recovery of the turf at this stage becomes a matter of encouraging regrowth of the thinned turf. If plant loss is severe, overseeding is required. For the summer leaf spot diseases, fungicide applications should begin as soon as the first leaf spots appear. |
Necrotic ring spot
(Leptosphaeria korrae)
Symptoms and signs:
Necrotic ring spot is one of three patch diseases caused by root pathogens that are problems of cool-season turfs. The other two are summer patch of bluegrasses and fine fescues and take-all patch of creeping bentgrass. Though not all caused by the same fungus, these diseases have similar patch-type symptoms, the causal fungi are related and similar in appearance, and these fungi attack grass roots and crowns in a similar manner.Symptoms of necrotic ring spot appear as circular, ring-shaped, or serpentine patches of dead or dying turf. Affected areas may be a few centimetres to a 300mm or more in diameter. These patches may at times coalesce, or they may stand out as individual dead rings. Leaves and stems of affected turf appear yellow or red, then turn a light tan as the disease progresses. Roots and crowns of diseased plants are rotted and recovery of affected areas is slow. Necrotic ring spot seldom occurs in newly planted turf but can occur on turf that has been recently sodded. It may begin during the fourth or fifth year following seeding and can become progressively more severe.
Disease Cycle:
Leptosphaeria korrae grows on the surface of grass roots for most of the growing season without causing visible symptoms. When conditions become favorable for the disease, the fungus attacks and destroys the roots. It is unknown if spores are responsible for transporting the pathogen from one area to another. Environmental conditions that favor necrotic ring spot may vary from one location to another. In some locations, the disease is more severe during the cool periods of spring and fall, whereas in other areas, the disease occurs only in midsummer. Necrotic ring spot is generally more severe on drought-stressed turf, but can damage turf growing in moist soils as well
Cultural Control:
To keep necrotic ring spot to a minimum, use cultural practices that reduce turf stress, such as irrigation during periods of drought stress and mowing lawn grasses at two inches or higher. The most effective way to manage necrotic ring spot in a home lawn is to use perennial ryegrass to overseed affected areas. Perennial ryegrass is highly resistant to this disease. Also, some benefits may result from overseeding Kentucky bluegrass varieties that are resistant to necrotic ring spot.
Chemical Control:
Most systemic fungicides will provide some control of necrotic ring spot when applied on a preventive basis. However, results are often erratic and the cost of the treatment is usually too high for most home lawn situations. |
Powdery Mildew
(Erysiphe graminis)
Symptoms and signs:
This fungus first appears as isolated wefts of fine, gray-white, powdery growth on the upper surface of the grass leaf. This growth rapidly becomes more dense and may cover the entire leaf, giving the leaf a gray-white appearance. In severe outbreaks, entire portions of the turf stand may be dull white, rather than green. Individual leaves look as though they are covered with flour or white powder.
Disease Cycle:
The organism overwinters in dead grass and in infected living grass plants. Spores of the fungus spread by wind to leaves of other turfgrass plants. Conditions favorable for the development of powdery mildew include poor air circulation, high atmospheric humidity (but no free water on the leaf surfaces), low light intensity or shade, and cool air temperatures. Kentucky bluegrass, when planted in shaded areas, is particularly susceptible to this disease.
Cultural Control:
Where occurrence of powdery mildew is frequent, changing landscape plantings to improve air drainage and reduce turf shading will aid in disease reduction. Prune overstory trees to allow sunlight to reach the turfgrass. Turfgrass species differ in their susceptibility to powdery mildew. Kentucky bluegrass, for example, is quite susceptible to this disease, whereas the fine fescues and tall fescue are quite resistant.
Chemical Control:
Fungicides, except for highly managed turf areas, are not necessary. |
Pythium blight
(Pythium blight)
Symptoms and signs:
Pythium blight, also known as grease spot and cottony blight, can be a highly destructive turfgrass disease, especially on bentgrasses and ryegrasses. Severe outbreaks can completely destroy the turfgrass within a few days if weather conditions favor disease development.Pythium blight first appears as small, irregularly shaped spots ranging from 10-100mm in diameter. Leaves appear water-soaked in appearance at first, then shriveled. Diseased patches fade to a light brown or gray color. Groups of spots frequently join together. At times, the shape of the affected areas may resemble elongated streaks. Both the presence and pattern of these streaks seem to be determined by the flow or presence of surface water. With high humidity in early morning or throughout the day, diseased leaves may be covered with the white, cobwebby, moldlike growth of the causal fungus.
Disease Cycle:
Pythium fungi may survive for long periods in the soil. In turf with a past history of Pythium blight, infected plant debris from the previous season or fungus spores in the soil are sources of infection. Disease development from the first infection centers occurs by growth of fungal mycelium and movement of spores from plant to plant. Under conditions favorable for disease development, Pythium blight can spread very rapidly.Primarily a warm, wet weather disease, turf blighting and disease development will be most rapid and severe at air temperatures from 30° to 35° C. As the air temperature approaches 35° C, destruction of grass stands can occur in a very short time. Pythium blight develops more rapidly when nitrogen levels are high, and more slowly under moderate or low nitrogen fertilizer programs.
Cultural Control:
In problem areas, satisfactory plant growth maintained through moderate fertilizer applications provides the least risk of Pythium blight damage. Kentucky bluegrass, the fine fescues, and tall fescue are less susceptible to Pythium blight than perennial ryegrass and bentgrasses. Providing adequate water and air drainage, especially where susceptible grasses are grown, can help control this disease.
Chemical Control:
Timing of fungicides is important. If continued hot, wet weather is expected, the first spray should be applied as soon as symptoms develop. On high value turf, such as golf course putting greens, tees, and possibly fairways, preventative fungicide applications may be justified. |
Red Thread and Pink Patch
(Laetisaria fuciformis and Limonomyces roseipellis) 
Symptoms and signs:
These two diseases present similar symptoms and appear as irregularly shaped patches of blighted grass. From a distance, affected areas have a reddish or pinkish cast. These diseases are usually restricted to the leaves, leaf sheaths, and stems, but in severe cases, may kill the entire plant. In the early stages of infection, symptoms appear as small blighted areas on leaves that enlarge rapidly to cover most of the leaf. Affected leaves dry out and fade to a bleached straw color. During moist weather, the leaves may become covered with the pink gelatinous growth of the causal fungi.Diagnosis of red thread is most certain in the advanced stages of disease development, when bright thread-like coral pink fungus mycelium, 2-6mm in length, are produced at the tips of the affected leaves. In the case of pink patch, affected leaves are covered with the pink fluffy growth of the causal fungus.
Disease Cycle:
The fungi overwinter as a dried gelatinous mycelium covering on infected dead leaves or in clipping debris from previously infected plants. The fungi spread by transport of mycelium or infected leaves to new areas. The mycelium on living, infected plants are easily broken loose and transported mechanically. The fungus enters the leaves through natural openings and cut tips, and spreads rapidly through the remainder of the leaf. Red thread and pink patch diseases develop more readily when air temperatures are 15° to 25°C, with prolonged periods of rainy or humid weather. At times, the disease occurs in warmer, drier weather.
Cultural Control:
Where red thread or pink patch causes turf damage, maintenance of adequate nitrogen levels for turf growth usually will reduce the problem. Turf managers should be aware, however, that at high nitrogen levels other diseases, such as leaf spot and brown patch, may become damaging.
Chemical Control:
In most turf situations, these diseases are not sufficiently severe to warrant fungicide treatment. Occasionally, however, pure stands of ryegrass or fine fescues may become severely blighted during wet weather. In these instances, fungicide treatment will minimize symptoms. |
Rust diseases
(Puccinia spp)
Symptoms and signs:
There are a number of rust diseases that affect turfgrasses. A few of the more common rusts that occur on cool-season grasses include stem, stripe, crown, and leaf rust. Although there are differences among these diseases with respect to the symptoms and portion of the plant affected, they generally occur under the same environmental conditions.Early infection appears as a light yellow flecking of the leaves. As these flecks enlarge, they may become somewhat longer than broad and when numerous they are arranged in rows parallel with the veins of the leaves. Soon, the epidermis ruptures and the spots develop into reddish-brown pustules. Severely infected plants have an appearance similar to rusty-iron, hence the name rust. When infected leaves are rubbed between your fingers or walked upon, a red powder collects on fingers or shoes. This powder is composed of millions of tiny spores of the fungus. Rust is normally a late summer or early fall problem and does not occur during other times of the year.
Disease Cycle:
The cycle of development for rust diseases is quite complex. Of the dozen or so species of rust fungi that affect turfgrasses, all but three go through five distinct spore production stages. Some of these stages, which are necessary for the completion of the entire life cycle, must occur on plants that are unrelated to the grasses. For a specific rust species, completion of the rust life cycle may require grasses and woody shrubs or grasses and herbaceous ornamental plants. In general, rust diseases do not kill turfgrasses, but may weaken them to the point that they become more susceptible to stress-related problems.
Cultural Control:
Adequate nitrogen and irrigation to maintain growth through late summer will minimize rust infections. In most years, the disease will not become severe, although infected turf may become yellowish-orange.
Chemical Control:
Fungicides are used only as a last resort; one or two sprays applied after the onset of symptoms usually will suffice. |
Slime molds
(Mucilago, Physarum, and Fuligo spp.)
Symptoms and signs:
Slime molds are different from most other turfgrass pathogens in that they do not directly infect the plant. Instead, this group of organisms feeds on microorganisms and decaying organic debris. During periods of warm, wet weather, slime molds migrate onto the surfaces of turfgrass leaves where they produce massive amounts of their reproductive structures, thus producing a white, blue, or gray patch.Grass blades and the surface of the soil may be covered with a translucent slimy, creamy-white growth. In a few days, this slimy growth changes to pinhead-sized masses of various colors (usually gray or blue). The affected areas may be from a few centimeters to many metres, with shapes ranging from rings to streaks or patches.
Disease Cycle:
Slime molds survive adverse conditions in the spore stage. In cool, humid weather, the spores absorb water. The spore wall cracks open, and a motile spore emerges. The motile spores feed on other microorganisms and decaying organic matter, but do not infect living turfgrasses. Eventually, pairs of spores unite and increase in size. This form of the organism is called a plasmodium, and it is this stage that produces the slimy overgrowth on turfgrasses. Slime mold plasmodia and reproductive structures may shade the grass leaves to the extent that leaves are yellowed, but damage seldom is severe.
Cultural Control:
Slime molds do not damage turf (apart from shading) and can be removed by sprinkling the leaves with water after the onset of dry weather. Removal of the dry spore masses by mowing, raking, brushing, or sweeping with a pole will aid in returning the grass to normal appearance.
Chemical Control:
Chemical control is not necessary. |
Summer patch
(Magnaporthe poae) 
Symptoms and signs:
Summer patch, sometimes called Poa patch, occurs on Kentucky bluegrass and fine fescues on lawns and grounds, and on annual bluegrass on golf course greens and fairways.Symptoms of summer patch on lawns, grounds or golf course fairways appear identical to necrotic ring spot. Hence, diseased specimens may have to be examined by a qualified diagnostician if positive identification is necessary. On putting greens, summer patch may begin as small (50-75mm) circular patches that progress to larger (up to 300mm) patches if conditions favor disease development. More often, large patches will appear suddenly with no indication of previous disease activity. In severe cases, the patches may coalesce and destroy large areas of turf. The patches initially take on a yellow color, then turn tan or a straw-brown color as the plants die. On greens with mixed annual bluegrass/bentgrass populations, the bentgrass usually will colonize the center of patches of affected annual bluegrass, creating a ring-shaped appearance.
Disease Cycle:
The causal fungus, Magnaporthe poae, colonizes grass roots in advance of disease causing activities. When conditions are favorable for disease activity, the fungus will invade the roots. Summer patch commonly occurs in midsummer during extended periods of high temperatures (>28°C) following wet weather or heavy irrigation. The disease does not appear during the cool weather of spring and fall. Summer patch is more frequently observed in areas that receive heavy traffic, poor air circulation, and inadequate drainage.
Cultural Control:
Since summer patch is a root disease, cultural practices that promote good root growth will aid in reducing disease severity. Increased aeration and improved drainage on compacted and poorly-drained soils will alleviate some root inhibition and enable the turf to better resist infection by Magnaporthe poae. Because low mowing heights are conducive to shallow rooting, raising the height of cut may result in less summer patch injury.
Chemical Control:
On golf courses, summer patch can be controlled with fungicides provided that applications are made on a preventative basis (3 to 4 weeks prior to symptom development) and high rates of systemic fungicides are used. Application of fungicides with large amounts of water (20-40 litres per 100m²) has provided superior control in some locations. Chemical control of summer patch in lawns is generally considered too expensive. |
Take-all patch
(Gaeumannomyces graminis)
Symptoms and signs:
This disease has been called Ophiobolus patch or Gaeumannomyces patch. Only bentgrasses are susceptible, so it is seen most commonly on golf course greens and fairways, where it can cause serious turf losses.Take-all patch usually appears in the late spring or early summer as reddish-brown or yellow areas of dead grass. Infection centers appear as rings, crescents, or spots in pure bentgrass stands. The center of the patch often is invaded by annual bluegrass or other weeds. In mixed stands of turf, the bentgrass is killed and other grasses in the stand remain. Affected areas may enlarge as much as 150mm or more in a year and eventually will exceed 1 meter. The symptoms become most conspicuous after turf has been stressed from hot, dry weather, even though moist, cool conditions favor infection and growth of the causal fungus. Dead or dying roots may be covered with dark brown strands of fungus (runner hyphae), and dark brown to black mats of fungal growth may be present on the stem bases beneath the leaf sheaths and on the crowns and roots of the killed tillers.
Disease Cycle:
Take-all patch is most frequently observed on bentgrass planted in recently fumigated soils and/or in recently cleared forested or wetland areas. In these situations, the beneficial microorganisms that compete with or antagonize Gaeumannomyces are present in low populations. In most cases, the disease will decline over a period of 4 or 5 years, a phenomenon thought to be associated with the build-up of antagonistic microorganisms. The causal fungus grows on the surface of bentgrass roots and attacks the roots in cool, wet weather, although the symptoms do not appear until warm, sunny weather occurs.
Cultural Control:
Since disease damage is, time-wise, removed from the symptoms, it is important to implement control measures prior to symptom development. Bentgrass take-all is most serious in soils with pH above 6.0. In some cases, liming appears to stimulate the fungus. At present, the only effective control known for bentgrass take-all patch is the use of some form of sulfur or an acidifying fertilizer such as ammonium sulfate or ammonium chloride. Ammonium sulfate should be applied and watered-in two to four times yearly, in spring and fall.
Chemical Control:
Some of the broad-spectrum systemic fungicides may control this disease if applications are timed to prevent fungal invasion of bentgrass plants in cool, wet environments. However, results obtained from fungicide applications are erratic and rarely give complete control. |
Yellow patch
(Rhizoctonia cerealis)
Symptoms and signs:
Yellow patch, which sometimes is referred to as cool temperature brown patch, occurs primarily on bentgrass and annual bluegrass putting greens, but may occasionally be found on Kentucky bluegrass lawns.On putting greens, this disease becomes visible when snow melts and appears as tan, brown, or yellow rings up to 600mm in diameter. The blighted turf usually is located around the periphery of the patch, leaving healthy appearing turf in the center. Damage from yellow patch usually is superficial, but significant turf loss can occur following prolonged snow cover or during prolonged cool and wet weather in early spring. Rings may appear on high cut turf as well, but rarely cause serious damage.
Disease Cycle:
Rhizoctonia cerealis oversummers as dormant resting structures and begins disease-causing activities during cool, wet weather at temperatures of about 4°C. The disease frequently develops under prolonged snow cover, but does not require snow cover to produce symptoms. The fungus primarily attacks the leaf blades of turf, but can infect crowns and roots.
Cultural Control:
Maintaining adequate levels of soil nutrients will help turf resist severe thinning by this disease. Improved surface and subsurface drainage will aid in reducing surface moisture that provides favorable conditions for disease development. Also, timely removal of winter greens covers will help surface drying and will reduce some disease incidence. Light applications of nitrogen fertilizer in the spring will quicken turf recovery from this disease.
Chemical Control:
Preventative applications of broad spectrum fungicides in late fall and/or winter may help to reduce disease severity in winter or early spring. |
|