Red thread

Laetisaria fuciformis

also called pink patch

Bleached patches of lawn threaded with tiny pinkish-red needles of fungus; a sign the turf is short of nitrogen rather than truly sick.

Fungus Disfiguring Airborne sporesSpread in waterSpread on tools & hands Spreads to neighbors

What you'll see

Fine reddish-pink threads or needles poke from the leaf tips, easiest to see when damp.
Irregular patches of grass turn tan, bleached, or pinkish.
Affected patches are ragged-edged and a few centimeters to a foot across.
A faint pink candy-floss webbing may show in humid mornings.
The roots and crowns stay healthy, so the grass recovers.

Why it happens

Red thread is a fungal disease of lawns caused by Laetisaria fuciformis. It lives in the leaf blades and spreads on air currents, water splash, mowing, and shoes, but it rarely kills the plant outright.

It appears in mild, damp weather from late spring to autumn and is far worse on hungry turf short of nitrogen, and on lawns left wet overnight.

Treating it

Feed the lawn with a balanced nitrogen fertilizer, which usually clears it as the grass grows away.
Collect and bin the clippings while the disease is present rather than returning them.
Improve airflow and drainage, and avoid watering in the evening.
Mow regularly at the right height with clean blades.

Keeping it away

Feed the lawn adequately through the season so it is never starved of nitrogen.
Scarify and aerate to reduce thatch and relieve compaction.
Water in the morning and deeply rather than lightly at night.
Keep mower blades sharp and clean to reduce spread and stress.

Who gets it

Lawns and fine turf, especially hungry ryegrass and fescue swards.