How to Identify and Treat Lawn Diseases

Is something on your lawn not looking right? You can use this guide to help you identify and treat common lawn diseases.

Even when you keep your lawn in good care, the grass can still become infected with various lawn diseases that lead to dead or discolored areas.

Lawn disease

Common Lawn Diseases and How to Treat Them

Brown Patch

Grasses typically affected: Tall Fescue, Perennial, Ryegrass, Bentgrass, Kentucky Bluegrass, St. Augustine.

Brown patches usually affect lawns in a hot, humid environment. It usually shows up as large, somewhat irregular patches that appear dry or dead. With St. Augustine grass, brown patches have a brown interior with a yellow outer ring.

How to treat: Water lawn early in the morning, aerate and dethatch

Red Thread

Grasses typically affected: Bermuda, Bluegrasses, Fescues, Bentgrasses, Perennial, Ryegrass.

Red thread usually affects lawns in cooler, humid environments like those in the Northwest and temperatures between 40-80 degrees. The red thread shows up most frequently in lawns grown in nutrient-poor soils. To identify this disease, you’ll find thin red stands coming from the grass blades.

How to treat: The basic treatment for the red thread is to fertilize your lawn with the proper amount of nitrogen as part of an ongoing feeding program.

Rust Disease

Grasses typically affected: Zoysia, Perennial, Ryegrass, Kentucky Bluegrass.

Rust disease appears as irregular light-green or yellow patches on the lawn, but when taking a closer look, you’ll see orange-yellow rust spores on the individual grass blades. This disease appears in the late summer and fall, especially in shady areas. This can also be a result of improper fertilization.

How to treat: minimize the amount of shade your lawn gets. Apply fungicides to grass areas with rust disease before it goes dormant for the winter. Rust disease may go away on its own if it’s properly fertilized.

Snow Mold

Grasses typically affected: Ryegrass, Creeping Bentgrass.

There are two types of snow mold: pink snow mold and gray snow mold. While snow mold generally grows under snow cover, pink snow mold can grow during cool, wet weather with no snow on the grass. You can identify this disease by looking for grey-white or pink-white patches of crusty, matted grass. This is more noticeable in the early spring when the snow begins to melt and evaporate.

How to treat: gray snow mold doesn’t kill the roots, so your grass may bounce back from it. For areas with pink snow mold, rake away dead grass and reseed bare patches.

Summer Patch

Grasses typically affected: Kentucky Bluegrass, Fescues, Annual Bluegrass, Bentgrass.

Summer patch usually appears between June and September, during periods of high humidity when daytime temperatures are above 85 degrees. It will appear in irregular brown patches, rings, and crescent shapes. Symptoms of the disease are less apparent during cooler weather.

How to treat: Aerate compacted soil, mow at your grass type’s highest recommended mowing height, create a fertilization plan, water your lawn early in the morning, reseed affected areas, and minimize soil compaction.

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