Disease Control

Brown Patch ( rhizoctonia blight)

Alternative Names:

Rhizoctonia blight

Description:

Brown patch presents itself on the lawn in the form of circular brown patches. These can range in size from a few inches to several feet in diameter. In the early morning dew, strands of a cobwebby fungal growth called mycelium may be evident on the grass blades. The affected grass will discolor, and in severe cases may die.

Causes:

Turf disease, a lack of sunlight, insect damage

Dollar Spot ( sclerotinia homeocarpa )

Alternative Names:

Sclerotinia homeocarpa

Description:

Large, tan colored wounds appear on the grass blades after fungus enters the grass plants when they are wet. These infected grass blades form rounded, damaged patches the size of a silver dollar. If the disease becomes more serious, the patches will expand and damage the entire lawn.

Causes:

Caused by a fungus which appears at temperatures between 60 and 90 degrees Fahrenheit. Thrives in times of warm days, cool nights, and morning dew.  

Fairy Ring ( marasmius oreades )

Alternative Names:

Elf rings, pixie rings, marasmius oreades

Description:

Fairy ring first appears as a circle of dark green, lush, fast-growing grass. A brown dead ring of grass surrounds the lush area. Rings or crescents commonly vary from 3 inches to 49 inches.

The fungus can show various symptoms, such as circular stunted or dead grass zones, a darker green zone of grass on the outer ring, growth of grass and weeds in the center, mushrooms on the fairy ring fungus, and a whitish fungus located above the soil surface.

Causes:

The disease is spread throughout the lawn in the form of spores. These spores are spread by wind, air, water, and humans.

Fusarium Patch (monographella nivalis )

Alternative Names:

Snow mold, microdochium patch

Description:

A disease in turf grass that causes small reddish-brown spots that are 1-2 centimeters in diameter.

Causes:

Caused by a fungus that attacks fine turf and generally affects cold season grasses. Following persistent cool, wet weather, new patches may spread.

Leaf Blight ( ascochyta spp. )

Alternative Names:

Ascohyta spp.

Description:

In heavily infested patches, the fungus damages the lawn in circular or tubular patches that often form large bleached areas. Close inspection of the plant reveals individual leaves drying from the tip down, with a brownish-purple line running horizontally across the plant.

Causes:

Occurs on lawns during hot, humid weather. The disease enters the grass plants after evening mowing when followed by excessive night watering.

Powdery Mildew ( erysiphe graminis)

Alternative Names:

Erysiphe graminis

Description:

Early stages are recognized as isolated colonies of whitish fungal structures called mycelia. Mycelia colonize and infect a large portion of the leaf blade with a whitish-gray dusty powder.

Heavily infected leaves can turn yellow, then brown, before dying. Colonies of powdery mildew darken with age and sometimes transform into dark, fruiting bodies.

Infected plants are weakened, becoming more susceptible to other stresses.

Causes:

This disease is a parasitic form of a plant life called fungi. Fungi live in the soil thatch and dead leaves all year round, and feed by drawing nutrients from the grasses.

Periods of low light intensity and poor air circulation favor the disease, and heavily shaded areas are particularly susceptible.

Red Thread (laetisaria fuciformis)

Alternative Names:

Laetisaria fusiformis

Description:

Under ideal conditions, the fungi appear as small red filaments that may be seen projecting out of the affected leaves.

Causes:

Red thread attacks most types of grass, but is generally found on lawns that contain high proportions of the Fescue species.

Factors that encourage the spread of red thread are poor air circulation, poor drainage, and a thatch layer greater than a ½ inch.

Rust Disease ( pucciniales )

Alternative Names:

Pucciniales

Description:

Rust often appears in the form of yellowy-orange flecks on the leaves and tips of grass plants. The spores soon enlarge to form round pustules that rupture to release powdery spores.

Causes:

This disease generally appears on lawns in late summer and fall, when there are conditions of low light intensity and temperatures between 70 and 80 degrees Fahrenheit with high humidity.

Alternating weather patterns with changes from cool, wet weather to hot, dry conditions can also create suitable conditions for the disease.

Yellow Patch

Alternative Names:

N/A

Description:

Yellow patch causes the turf to form patches that are yellow, light brown, or reddish-brown in color and measure from 5 inches to several feet in diameter.

Damage is usually superficial, but thinning can occur with prolonged periods of wet weather in the late winter and early spring.

Causes:

Fungi that live in the soil, thatch, and dead leaves in the lawn feed on the grass by drawing nutrients from the plant and destroying the plant cells.

Yellow patch spreads in the form of spores throughout the lawn by wind, air, water, and human traffic.

The disease may re-appear from year to year if conditions are favorable. As a general rule, areas that have been prone to disease problems in the past will have the same problems again.