Turfmate field notes · Diseases

Pythium root rot

Pythium species, a group of water moulds.

Pythium root rot can cause thin, discoloured turf that appears to wilt even when the soil is wet. Its surface symptoms vary, so the most useful checks are below the canopy. Australian guidance identifies it particularly with intensively maintained golf and bowling greens.

Yellowing and scattered brown-red areas associated with Pythium root rot in older bentgrass varieties.
Yellowing and scattered brown-red areas associated with Pythium root rot in older bentgrass varieties.
Photo: Pete Dernoeden, Ph.D / Syngenta GreenCast · Full photo ↗

What to look for

  • Irregular yellow, bronze, reddish-brown or purplish areas that look weak, wilted or slow growing.
  • Thinning concentrated around wet ground, drainage routes or areas repeatedly stressed by mowing and traffic.
  • A reduced root system, discoloured roots or water-soaked crown tissue, rather than obvious cottony leaf growth.

More photos to compare

Compare the overall pattern with the plant detail. Check the grass species and growing conditions as well as the appearance.

Pythium root rot on dense bentgrass, showing purple-brown spots and irregular patches.
Pythium root rot on dense bentgrass, showing purple-brown spots and irregular patches.
Photo: D. Bevard / Syngenta GreenCast · Full photo ↗

Check the grass and site

Mature cool-season and warm-season turf can be affected, including bentgrass, wintergrass (Poa annua) and couch. The photographs show bentgrass.

Confirm it before you treat it

These symptoms overlap heat stress, drainage problems, nutrient issues and other root diseases. Examining affected plants and roots, often through a diagnostic service, is more reliable than colour alone. Keep notes on grass type, rainfall, irrigation and the pattern of decline.

What to do next

  1. Check soil moisture and drainage before increasing watering; avoid keeping the root zone saturated.
  2. Reduce mowing and traffic stress, reviewing the height of cut and repeated passes over damaged edges.
  3. Plan aeration, thatch management and improved airflow to support roots when conditions allow the turf to recover.
Seasonal watch

Conditions matter more than dates.

Wet soils are the main shared risk across the different Pythium species involved. Heat, shade, close mowing and wear can make symptoms more severe. Poorly drained or repeatedly irrigated areas deserve particular attention.

Why can root rot look like drought in wet ground?

Damaged roots struggle to supply the plant with water and nutrients. Leaves can therefore wilt despite wet soil. Check moisture and root health before simply extending irrigation times.

Compare similar problems

Reviewed 18 October 2026 · Turfmate. Identification guidance is not a laboratory diagnosis or a spray calendar.

Technical sources & image credits

Syngenta photographs are reproduced in full with attribution. Source grass species and settings are identified where supplied; photographs support identification and do not replace diagnosis.

A Turfmate product link does not imply endorsement by a photographer or source.