The Byer Family Resource - Lawn Care

COMMON TURF DISEASES

All grasses are susceptible to diseases, most often fungi. There are hundreds of different disease-causing fungi and under stressful conditions, such as temperature and humidity, they can cause severe damage. Turf is most susceptible to fungi attack during its maximum growth periods (spring and fall).

Other factors that can reduce the resistance to diseases are the over-excessive application of nitrogen, cutting grass too short, watering in the evening leaving grass wet over night and leaving the clippings on the turf after cutting.

The following is a list of the most common turf diseases seen in Southern Ontario. They will be listed by their common names and we will try to include symptoms, what grasses are susceptible, the conditions that contribute to the disease and how to control the problem.

Pink Snow Mold

Fusarium Blight (Necrotic Ring Spot)

Melting Out

Brown Patch

Anthracnose

Dollar Spot

Red Thread

PINK SNOW MOLD or FUSARIUM PATCH

Symptoms - Fusarium patch can appear at any time of the year but Snow mold is usually

seen following the melting of snow. The appearance of the infested areas are irregularly

circular, ranging from a few inches to more than a foot in diameter. Diseased areas are

pink or pale yellow at first becoming bleached or tan as disease progresses.

Grass blades feel slimy when wet.

Susceptible Grasses - Most northern turfgrasses are susceptible - annual Kentucky and

rough bluegrass, Colonial, bentgrass, ryegrass, fescues and others.

Contributing Conditions - The most common condition contributing to pink snow mold is

when snow cover occurs over unfrozen soil. Fusarium patch generally appears

when there are periods of high relative humidity with air temperatures of 32 to 62F.

This fungus becomes dormant at temperatures above 70F. Severity of these

diseases may also be increased the presence of heavy thatch.

Control - Avoid excess thatch, rake lightly to loosen compactness and remove

dead grass, allow to dry out, apply fertilizer and fungicides can be

used to prevent further damage.

FUSARIUM BLIGHT (Necrotic Ring Spot)

Symptoms - Diseased areas first appear light green but fade to tan and then light straw cover

in a 36 to 48 hour period. Shapes range from roughly circular to crescents and elongated

streaks and the size of the affected area ranges from 2 inches to several feet in diameter.

This disease also may develop into the "frogeye" effect, circular straw colored

patches with tufts of green grass in the center.

Susceptible Grasses - Bentgrasses are the most susceptible to blight, followed by Kentucky

bluegrass, red fescue and annual bluegrass. However, there are other turfgrasses

that are suseptible. New varieties of bentgrass and bluegrass

have moderate to good resistance to Fusarium blight.

Contributing Conditions - Fusarium blight is most severe during periods of prolonged

high humidity and daytime temperatures of 80 to 95F and nighttime temperatures

of 70F or greater. Low calcium soils and drought stress also aggrevate the disease.

Control - Maintain a good lawn maintenance program and fungicides can be used

to reduce further damage.

MELTING OUT

Symptoms - Also called Leaf Spot, Going Out and Leaf Blotch, this diseases symptoms

include thinning out of grass in scattered areas, browning of affected plant,

circular to elongated purplish, brown to dark brown or reddish brown patches

with white, tan, brown or straw-colored centers on grass blades. In hot,

windy weather, these plants generally die.

Susceptible Grasses - Most grasses grown in Southern Ontario are susceptible. These

include Kentucky bluegrass, ryegrass, bentgrass, bermudagrass and fescue.

Newer varities of bluegrass show moderate resistance to this disease.

Contributing Conditions - Melting Out and the other similar diseases listed above, appear

over a wide range of temperature conditions (50 to 90F) under high humidity.

Melting Out usually occurs during warm dry summer months and then re-appears

with the onset of cool wet weather. Leaf Spot generally appears on grasses

in shaded areas and is most severe and damaging on grass that is cut too short.

Leaf Blotch damages young seedlings or adult plants weakened by excess thatch,

insufficient nitrogen and unfavorable growing conditions.

Control - Avoid excess thatch build-up, frequent waterings, cutting lawn to short and

excessive applications of nitrogen. Fungicides, again, can be applied to

avoid further damage.

BROWN PATCH

Symptoms - Brown patch occurs in circular areas ranging from a few inches to several feet in

diameter. Blades first appear water-soaked and dark-colored, then wilt and

become light brown. In the beginning stages, a patch may be largely green

with only a slight discoloration but as it worsens, the affected area

becomes larger and distinctly brown in color.

Susceptible Grasses - Bentgrass, bluegrass, bermudagrass, ryegrass, fescue and others.

Contributing Conditions - Excess thatch and mat, high humidity, high temperatures

(75 to 95F) and soft lush growth.

Control - Avoid excess thatch build-up, keep grass vigorous with fertilizer and

water and apply a fungicide to reduce further damage.

ANTHRACNOSE

Symptoms - The first symptom is yellowing patches of blighted turfgrass, then these areas

will become bronze in color and fade to tan if the disease is not controlled. These areas range

from 2 inches to 20 feet in diameter. Lesions on the blades are elongated

reddish-brown blotches. As the blades dry out, small black bumps covered with rows

of black spines can be seen.

Susceptible Grasses - Most commonly grown turfgrasses susceptible with annual bluegrass

usually being most affected.

Contributing Conditions - This disease is most prevelent during prolonged periods

of warm, wet weather with high relative humidity and high temperatures of 80 to 90F.

The severity is increased by poor or imbalanced fertilizer, excess thatch

and the presence of other diseases or insect pests.

Control - Avoid excess thatch, apply well-balanced, good quality fertilizer and

fungicides can be used to reduce further damage.

DOLLAR SPOT

Symptoms - Light tan with reddish-brown bordered lesions that extend down the blade from

the tip to 1 or more inches in length. During morning hours, wisps of white threads may

be seen on diseased turf. Affected areas are usually about the size of a silver dollar,

hence the name dollar spot. Rarely do the spots grow any larger but if not controlled,

they can become so numerous that they will overlap to produce large,

irregular shaped areas of dead turf.

Susceptible Grasses - Annual bluegrass, bermudagrass,colonial bentgrass, Kentucky

bluegrass, red fescue and others.

Contributing Conditions - Moderate temperatures (60 to 80F) and excess moisture, excess

thatch and insufficient nitrogen are contributors to this disease.

Control - Reduce the amount of thatch, increase supplies of good quality fertilizer

and water less frequently but more volume.

RED THREAD

Symptoms - Coral-pink to red fungus strands that bind leaves together. Areas are usually

circular in shape and measure 2 to 15 inches in diameter. When dry, the pink strands

look like red threads. The first appearance usually seems water-soaked but

soon dies, becoming light tan.

Susceptible Grasses - Bentgrass, bermudagrass, bluegrass, fescue & ryegrass.

Contributing Conditions - Red thread is most serious during periods of prolonged cool, wet

weather, especially on turf deficient in nitrogen.

Control - Avoid watering during cool weather & apply high-quality fertilizer.

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Common Turf Damaging Insects

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