Common Lawn Diseases | Their Types, Causes, Identification and Treatment

Who doesn’t love to have a lush green area around their home? A walk on the lawn relaxes your nerves and calms your soul. But does this serenity spot cost you some of your time and care?

The answer is yes. The property needs your attention and care to be healthy and green. If neglected, various microscopic organisms attack the grass and cause diseases in the lawn like in plants.

Are lawn diseases a threat to homeowners?

A lawn disease occurs when the leaf, crown, or root system of the grass is affected by a group of pathogens.

common lawn diseases

Lawn diseases can become severe when the climatic conditions and our cultural practices favor the pathogens’ growth. Identifying the pathogen or disease timely and altering the lawn care practices can help reduce its severity.

Unless the lawn is well maintained, there is no threat to the grass, and homeowners need not worry. Otherwise, the lawn will be susceptible to various diseases. Proper lawn care curbs the severity of the disease

The three significant factors causing diseases in the lawn are

  • Disease pathogens
  • Weather conditions that favor disease development
  • Susceptible lawn grasses (Host plants)

Though the weather is unpredictable, selecting the right grass and good cultural practices are essential to reduce disease occurrence and spread.

Some of the common diseases that can be seen in the lawn are the following,

    1. Brown patch disease
    2. Dollar spot disease
    3. Gray leaf spot disease
    4. Pythium lawn disease
    5. Red thread disease
    6. Rust disease
    7. Snow mold disease
    8. Summer patch lawn disease
    9. Powdery mildew disease
    10. Rhizoctonia yellow patch
    11. Ascochyta leaf blight
    12. Leaf spot
    13. White patch
    14. Copper spot

Brown patch disease

brown patch disease

Pathogen-Rhizoctonia solani

Host- Ryegrass, Kentucky bluegrass, fescue, bentgrass, centipede grass, St. Augustine grass

Brown patch disease is also known as Rhizoctonia blight and is harmful to Ryegrass and tall fescue.

It is a foliar disease that affects the leaf blades, excluding the root and crown regions.

The pathogen affects the cool season lawn grass.

Factors favoring the disease occurrence- brown patch disease occurs mostly in warm to humid weather conditions, especially in Spring and Fall. The disease is more prevalent when the temperature remains more than 65oF at night and occurs from May to September.

Cause: Excessive Nitrogen, over-irrigation, high humidity and the presence of wet leaves facilitate the spread of the disease.

Symptoms-

Circles of dead, hollow grass with brownish-yellow patches can be seen on the affected parts, ranging from 6-inch diameter to several feet wide.

Leaf-blades show white cottony growth in the early hours of the day.

Control-

Avoid over-fertilizing your lawn.

Irrigation practices should be appropriate. Avoid excess irrigation

Use Fungicides like Acti-dione, Tersan, Kromad to control the disease.

Dollar spot disease

dollar spot lawn disease

Pathogen-Sclerotinia homoeocarpa

Host- Kentucky bluegrass, bermudagrass, zoysiagrass, fine fescue, Ryegrass, bentgrass

It is also known as a small brown patch and occurs in nitrogen-deficient soils.

Kentucky bluegrass is severely affected by this disease

Factors favoring the disease occurrence- warm moist weather in the Spring and fall favors the disease occurrence. It occurs from May- September

Cause- under fertilizing, excessive moisture, drought stress, and thatch is the root for this disease

Symptom- silver dollar size circles spread up to 6 inches wide can be seen in the lawn

Control-

Apply adequate Nitrogen at the right time

Chemical treatment with cadminate, CaloCure, Kromad is suggested in extreme damage.

Gray leaf spot disease

Gray leaf spot disease symptoms
Grey spot in grass leaf (Credit: ncsu)

Pathogen-Pyricularia grisea

Host- perennial Ryegrass, tall fescue

The disease is also called blast.

Factors favoring the disease occurrence- moderate to high temperature with high precipitation from Spring to fall favors the development of Gray leaf spot disease.

Cause-

The disease is caused due to poor air circulation and over-fertilization. A shaded area near the lawn spreads the disease.

Symptoms-

Small irregular patches join together and form lesions.

Grey spots appear on the leaves and the affected area turns brownish.

Control-

Avoid excess Nitrogen in mid-late summer.

Timely irrigate the lawn.

Chemicals like thiophanate methyl can be used to control the disease.

Pythium lawn disease

Pythium blight
Pythium blight patches in the lawn (By John Kaminski)

Pathogen-Pythium spp. (P. graminicola /P. aphanidermatum)

Hosts- Perennial Ryegrass, creeping bentgrass, Kentucky bluegrass, and tall fescue

Newly planted grasses are more susceptible to this disease.

Pythium fungi cause two major destructive diseases.

Grease spot- occurs in a wide range of grasses.

Cottony blight- occurs mainly on Ryegrass.

Factors favoring the disease occurrence- warm temperature, prolonged wet conditions, and high humidity from early summer to fall favors the disease’s growth. The fungi are damaging in poorly drained soil with 70 oF and above temperature. The disease occurs from April- September.

Cause- excess fertilization and irrigation, compacted soil, and too much shade cause the disease.

Symptom-

A group of circular spots of 2-inch diameter is noticeable, especially in the early hours of the day.

Leaves appear slimy by soaking water and stick together.

Circles of withering can be seen on the lawn.

Control-

Avoid irrigation methods that keep the grass wet for a longer time.

Avoid excess watering in warm weather.

Fungicides like Captan, Zineb, Kromad, or any mercury-containing fungicide can reduce the disease’s severity.

Red thread disease

Red Thread Disease
Red Thread Disease symptoms (BY: Kris Lord)

Red thread lawn disease is caused by the pathogen Corticium fusiform.

Host- Red fescue, Ryegrass, Kentucky bluegrass, bentgrass

It is a relatively less damaging disease and affects cool-season grasses.

Factors favoring the disease occurrence- mild-early spring temperatures and cool-wet conditions with a temperature between 68-75°F and high humidity favor the growth of this fungus

Cause- under fertilizing, high humidity, poor air circulation, too much shade, excess thatch, leaves left wet for an extended period, and compact soil are the reasons for the disease.

Symptom- as the name implies, the disease can be identified with the appearance of webbing or thread-like fibers of red or pink color on the grass and the grass blade wither from tips.

Management-

Nutrient control, proper aeration, and soil improvement may help control the disease for a more extended period.

In extreme damage, treat the lawn with fungicides like strobilurins.

Rust lawn disease

rust lawn disease

Pathogen-Puccinia spp.

Host- Merion Kentucky bluegrass

Factors favoring the disease occurrence- mild to moderately warm temperature from early summer to fall incidents of the disease. It occurs from May- September.

Cause- drought, high humidity, extended wetness, too much shade, under fertilizing causes the disease

Symptom-

Orange-red powdery pustules cover grass blades.

Irregular patches appear on the leaves and stem.

Thinning of grass is seen during severe damage.

Control-

Optimal fertilization in the lawn

Follow regular mowing- avoid close mowing.

Mix different species of grasses while planting. Ex-mix Merion Kentucky grass with common Kentucky bluegrass at the ratio of 1:1 to prevent the severity. Mix Merion Kentucky bluegrass + red fescue at the ratio of 1:1

Irrigate the lawn in the early morning

Use chemicals like Acti-done, Zineb. They May affect the growth of Merion Kentucky grass for a week, but later the growth will be normal.

Snow mold lawn disease

Snow mold lawn disease
Snow mold in lawn

It is a fungal disease.

Factors favoring the disease occurrence: overly cool temperature combined with wet conditions, especially places under snow cover, favors the fungi’ incidence.

Cause: Over-fertilizing with too much Nitrogen in fall, poor drainage, too much shade and extended period of snow coverage causes the disease.

There are two types of snow molds.

Gray snow mold (Typhula blight)-

Pathogen-Typhula spp.

Hosts- Most cool-season grasses

It infects the leaf tissue

Symptom-

white to grey webbing appears on the leaf blades

Circular patches of light yellow or greyish brown color can be visible in severe damage.

Pink snow mold (Fusarium patch)

Pathogen-Fusarium nivale

Hosts: Bentgrass, bluegrass, fescue, and Ryegrass

It infects the crown region and is relatively more damaging than Typhula blight.

Symptom-

Greyish to pink webbing can be seen

Yellow patches will be formed in severe cases

Control-

Rake the damaged spots and leaves. It will reduce the moisture and help the grass to dry quickly.

Mow the lawn to a shorter height to minimize the moisture

Avoid application of Nitrogen during fall if your grass is susceptible to snow mold

Seeding with different variety of grass should be done if there is no growth

If the severity prevails, apply thiophanate methyl in the late fall.

Summer patch lawn disease

Summer Patch

Pathogen-Magnaporthepoae

Host- Kentucky bluegrass, annual bluegrass, fescue

Factors favoring the disease occurrence- hot and wet weather with compacted soil favors the disease’s growth. The disease is seen in July- August.

Cause- excessive soil moisture, compacted soil, poor drainage, and mowing too low roots the growth of the disease

Symptoms-

Circular patches of dead grass with yellow/ orange leaves

The roots and crown of the infected plants get discolored

Control-

Mowing at a higher height helps to prevent the disease occurrence

Adopt proper irrigation practices

Powdery mildew disease

Pathogen-Erysiphe graminis

Hosts- Bluegrass

It is a fungal disease common in most plant species.

The disease is prevalent on cold-season grasses, especially on Kentucky bluegrass.

Factors favoring the disease occurrence- temperature from 60 to 72 oF in cool and high humid regions favor the disease’s growth. It occurs in Spring and Fall, from March to September.

Cause: the lawn present in the shady areas, majorly during cloudy or overcast periods, attracts the fungus’ growth.

Symptoms- white powder-like dust forms on the leaf blades

Control-

Proper fertilization to avoid excess green growth

Selection of shade-tolerant species

Mowing at a higher height.

White Patch

Pathogen-Nelanotussps.

Host- tall fescue

The disease occurs mostly in immature grasses less than 2 years old.

Factors favoring the disease occurrence-  Hot and humid weather favors the disease occurrence.

Symptoms-

White patches of 1-2 feet in diameter can be seen.

Small white mushrooms may develop on the leaf blades.

Death occurs first from the tip and later moves down to the leaf sheath.

Control-

Maintain proper soil pH.

Proper irrigation practices should be followed.

Rhizoctonia Yellow Patch

Pathogen- Rhizoctonia cerealis

Host- Kentucky bluegrass

Effects grasses in heavy soil

Factors favoring the disease occurrence – cool, wet weather favors the disease growth. It occurs in grasses with compacted soil and heavy thatch.

Symptoms-

Light green-yellow colored patches of 2-3 inches

Patches may appear sunken.

Tan spots with dark borders may appear in the later stage.

Control-

Proper aeration of the lawn

Thatch control- kept less than a half-inch thick.

Removing soil compaction

Avoid excess nitrogen application in the spring.

Ascochyta Leaf Blight

Pathogen-Aschochytasps.

Host- Kentucky bluegrass, tall fescue, perennial ryegrass

Factors favoring the disease occurrence – hot drought periods preceding cool, rainy conditions are the source for the disease.

Symptoms-

Large- irregular patches appear, and the grass turns to straw color and appears dead.

Sometimes spots can be seen on leaf borders.

Control-

Reduce thatch.

Mowing regularly- maintain 2-3 inches height

Proper fertilizing- avoid excess nitrogen application in spring.

Irrigation should be appropriate.

Copper Spot

Pathogen-Gloeocercospora sorghi

Host-bentgrass, bermudagrass, Zoysiagrass

It is a foliar disease.

Factors favoring the disease occurrence – seen in moist acidic soils. Warm moist weather 68-86 oF favors the pathogen

Symptoms- pinkish-orange to copper-colored patches of 1-3 inch with irregular margin can be identified in the lawn

Management-

Remove early morning dew and waste.

Avoid mowing when leaves are wet.

Avoid using water-soluble nitrogen fertilizer when the disease occurs.

Leaf Spot

Factors favoring the disease occurrence – unseasonable warm temperature favor the disease occurrence in cool-season grasses

Cause- high humidity, extended moisture, mowing too short, and high nitrogen application favor disease incidence.

Symptoms-

Elongated, oval spots with brown centers appear on the leaves, and margins become dark purple-brown.

Crowns and roots turn dark brown; they get rot and die in severe conditions.

Control-

Irrigate the lawn in the early hours of the day.

Regular mowing on the lawn- avoid mowing too short.

Avoid excess application of nitrogen.

Compacted soil

The soils where traffic is heavy get saturated and packed heavily. They become dry and hard. This will resist the water from penetrating the surface. It results in thinning of the grass, and empty spots appear on the lawn.

Control-

Loosen the soil

Fertilize and reseed the grass if necessary

Diagnosis of a lawn disease

Review the lawn’s history- consider the details of fertilizer and chemical application, irrigation practices, soil, as most of the disease incidence is due to fertilizer born, poor irrigation practices, and chemical applications. Keeping in the record of cultural practices will help us know the reason for the disease occurrence, and these practices can be altered to reduce the disease.

Know your grass species and the time of year the damage began to appear- several pathogens infect few grass species. So it is critical to know your grass before you choose it. Sometimes, weather and time of the year contribute to the incidence of the disease. For instance, Wet conditions and warm temperatures favor diseases like Pythium.

Recognize the appearance of healthy grass- if you know how healthy grass looks, you can identify your lawn changes. Wilting, thinning, or empty patches in your lawn can be considered problematic.

Check for symptoms- different diseases show different signs and symptoms. If you find any unusual patterns in your lawn, look for the symptoms and remedies. You can refer to the symptoms of various diseases mentioned in this article.

Identify disease variability- several factors render variations in different diseases at different places. It may be caused by the amount of severity of the disease or the presence of more than one pathogen. Compare the disease pattern and consult your nearest lawn care expert for advice.

Management practices for preventing lawn diseases

Preventing the incidence of the disease is easier than controlling them once they occur. These are some of the measures to be taken to reduce the incidence of the disease.

Select the grass species that best adapt to the soil and climatic conditions. Seek the help of a lawn care expert near your area

Fertilize properly. Excess or low fertilizer can attract pathogens.

Water in the early mornings and avoid frequent watering, especially in warm weather.

Mow the grass regularly to prevent it from growing too tall

Dethatch lawns and aerate soil regularly.

Use pesticide for severe infection.

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