rusts and mildew

Rusts & Mildew

Rusts is a fungal disease noticed as a yellowing of the grass leaves. Mildew often looks like someone has painted the grass leaves white


Lawn rust as seen above, generally attacks in moderate temperatures most usually in late summer or early autumn particularly on already stressed turf. This stress often comes from drought and/or nutient deficiency but may also occur in constant wetness.

The disease is generally noticed as a yellowing of the grass leaves and on closer inspection with a loop or magnifying glass, you will see an orange powdery speckling on the leaf surface which easily comes off on to your fingers. These are the fungal spores ready for transfer to fresh grass leaves. As with red thread once the conditions improve there is no lasting damage to your lawn.


  • Maintain a good supply of nitrogen in the turf to promote growth. This enables the disease to be mowed out.
    • Use any Spring & Summer fertiliser to end August or Autumn fertiliser from August onward
  • Try not to use pesticides or weed and feed products during outbreak
  • DO water the lawn to relieve stress – see Watering the Lawn
  • Remove clippings after mowing


Mildew or powdery mildew is common in shady and or dry areas of lawn particularly on longish grass. It is seen as a powdery white covering and from a distance may look as if someone has lightly white washed the lawn!


I wouldn’t get too alarmed by this disease and manage it as follows if it occurs.


  • Be careful with fertiliser applications – apply low amounts on shaded grass
  • Try to reduce shade
  • Improve air circulation by thinning bushes
  • Remove clippings after mowing

Images courtesy of the STRI