Skip to main content

Red Thread

Home > Resources > Red Thread

What is Red Thread? Laetisaria fusiformis

Madison, WI Red Thread

  • A troublesome disease that infects lawns across the country
  • This disease is a parasitic form of plant life called fungi. Fungi live in the soil, thatch and dead leaves all year round. These fungi feed off the grass by drawing nutrients from it.
  • The disease spreads throughout the lawn in the form of spores. These spores are spread by wind, air, water and humans. The disease may be caused by improper mowing and watering (refer to Weed Man Mowing and Watering Fact Sheets for proper maintenance procedures). Discuss maintenance practices with your Madison, WI Weed Man.
  • Red Thread attacks most types of grass but is generally found on lawns that contain high proportions of the Fescue species.
  • Under ideal conditions the fungi appear as small red filaments that may be seen projecting out of the affected leaves.
  • Other factors that may encourage the spread of the disease are poor air circulation, poor drainage and a thatch layer greater than ½ “ (1 cm).


Controlling Red Thread can be achieved through modifying the lawn environment. The thinning of trees will improve air circulation and the penetration of sunlight. Core aeration will reduce the thatch layer and improve water penetration. Regular applications of a balanced fertilizer will produce a healthy lawn, which is more resistant to attacks by this disease. Have your Madison, WI Weed Man fertilize your lawn and advise you on correct maintenance to ensure a healthy disease free lawn.