Lawn Problem Solver

Red thread Fungal Disease

Laetisaria fuciformis

Red Thread is a fungal lawn disease that causes pink, red, or tan patches in turf, especially during cool, wet, humid weather. It is most common in cool-season lawns that are under-fertilized, slow-growing, or stressed.

Disease
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Red thread

What Red thread Looks Like

Red Thread usually appears as small to medium-sized tan, pink, or reddish patches in the lawn. The patches may look water-soaked, bleached, or straw-colored from a distance.

Up close, infected grass blades may have thin red, pink, or coral-colored thread-like strands extending from the tips of the leaves. You may also notice pinkish fungal growth on the grass during damp, humid weather. Red Thread often makes the lawn look patchy, thin, or off-color, but it usually affects the leaf blades more than the crown of the plant.

Why It Spreads

Red Thread develops when cool, wet, humid conditions combine with slow turf growth. It is especially common in lawns that are low in nitrogen, under-fertilized, shaded, compacted, or staying wet for long periods.

The disease spreads through infected leaf tissue, mowing, foot traffic, equipment, and wet grass blades. It is most common in spring and fall, but it can also appear during mild, rainy summer periods.

How to Prevent It

Prevent Red Thread by keeping the lawn healthy, properly fertilized, and actively growing. Follow a balanced fertilizer program for your lawn type, mow at the correct height, and avoid letting the lawn become weak or underfed.

Water deeply and early in the morning so the grass dries quickly. Improve airflow in shaded or tight areas, reduce compaction when needed, and avoid frequent light watering that keeps the leaf blades wet.

Best timing: Spring and fall before extended cool, wet, humid weather.

How to Control It

Red Thread often improves when turf growth increases and the lawn receives proper fertility. Apply the right fertilizer for your grass type and season to help the lawn grow through the disease and recover.

If Red Thread is severe, spreading, or recurring, use a fungicide labeled for Red Thread and safe for your lawn type. Apply according to the label, and rotate fungicide groups if repeat applications are needed.

Best timing: At the first sign of pink, red, tan, or straw-colored patches with red thread-like growth on grass blades.

Recommended Solution

Red Thread is usually a sign that the lawn is growing too slowly or does not have enough fertility to recover quickly. Start by improving the lawn’s overall health with proper fertilization, mowing, watering, and airflow. In many cases, the disease will fade once the grass starts growing more actively.

If the lawn has heavy red or pink fungal growth, visible thinning, or repeated outbreaks, apply a fungicide labeled for Red Thread. Pair treatment with good fertility and watering practices so the turf can recover faster and fill back in.

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Frequently Asked Questions

What causes Red Thread in lawns?

Red Thread is caused by the fungus Laetisaria fuciformis. It becomes active during cool, wet, humid weather, especially when lawns are under-fertilized, stressed, or growing slowly.

What does Red Thread look like?

Red Thread usually causes tan, pink, or reddish patches in the lawn. Up close, you may see red or coral-colored thread-like strands attached to the tips of infected grass blades.

How do I get rid of Red Thread?

Improve lawn growth with proper fertilization, mow at the correct height, water early in the morning, and improve airflow where possible. If the disease is severe or recurring, apply a fungicide labeled for Red Thread and safe for your lawn type.