Turfmate field notes · Diseases

Slime mould

Physarum and other slime moulds

A dramatic surface coating often needs reassurance, not a fungicide.

Magnified Physarum cinereum structures from an Australian observation. This microscope view is not a photograph of a lawn patch.
Magnified Physarum cinereum structures from an Australian observation. This microscope view is not a photograph of a lawn patch.
Photo: Peta McDonald · source · CC0. Displayed at reduced size; card crops fit the layout.

What to look for

  • Small coloured or grey structures coat leaves.
  • Patches can appear quickly after moist conditions.
  • The grass beneath the coating may remain healthy.

Confirm it before you treat it

Inspect the leaf underneath. Slime mould sits on the surface rather than infecting the grass, though a heavy coating can shade leaves. Rust pustules and rapidly collapsing diseased turf need a different diagnosis.

What to do next

  1. Take a close-up and confirm the coating before treating.
  2. Allow conditions to dry; gentle brushing or mowing can remove mature deposits where practical.
  3. Review persistent dampness if it recurs. A fungicide is usually unnecessary for slime mould itself.
Seasonal watch

Conditions matter more than dates.

Moist conditions allow the organism to develop and move onto leaves. It feeds on microorganisms and organic material rather than turf tissue.

Watch after damp spells, rainfall or irrigation; a fixed disease season is not a reliable test.

Explore your region & month ↗

Is every strange coating a lawn-killing fungus?

No. Confirm whether the grass itself is damaged. The two photos show the same Australian slime mould observation from different views.

Inspect & compare

More views. Better clues.

Read each caption and compare fresh symptoms in your own turf.

A closer microscope view from the same Australian Physarum cinereum observation. Microscopic structures complement, rather than replace, assessment of the grass surface.
A closer microscope view from the same Australian Physarum cinereum observation. Microscopic structures complement, rather than replace, assessment of the grass surface.
Photo: Peta McDonald · source · CC0. Displayed at reduced size; card crops fit the layout.
Keep investigating

Similar problems. Different solutions.

Reviewed 11 October 2026 · Turfmate. Seasonal windows are indicative planning guidance, not measured outbreak or prevalence data.

Technical sources & image credits

Photos support identification and may have been taken outside Australia. Appearance varies with species, mowing and conditions. A Turfmate product link does not imply endorsement by a photographer or source.