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Timely Tip – Red Thread

Red Thread is a Troublesome Lawn Disease

As the name suggests, Red Thread causes red / pinkish threads to appear on the lawn.
These threads are caused by a fungus that feeds off the grass by drawing nutrients from it.  Red Thread appears most commonly during cool, moist weather patterns in May and early June.  As the lawn dries out, the affected areas, usually several inches in diameter, take on a bleached appearance.  While red thread kills the grass blades, most often the grass plants survive and are able to recover.

What causes Red Thread

Red Thread can be much more prevalent in some years than in others.  Cooler, wetter weather in May and June seems to encourage the development of Red Thread.  The disease attacks all the commonly grown grass types in our area, including rye, bluegrass and fescue.  Poor air circulation, poor drainage, an excessive thatch layer greater than ½” and clay soils low in organic matter are factors that encourage the spread of red thread.


We do not recommend applying fungicides to residential lawn in our area for the control of red thread.  We find that if the pressure from appropriate weather and other factors is sufficient, fungicides offer relatively poor protection from the damage.  While the damage can be unsightly, the lawn is usually able to recover once the weather becomes drier and warmer.  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 Weed Man’s balanced, slow-release fertilizer will encourage the general health of the lawn and make it less susceptible to disease and insect problems.  Newer lawns with poor topsoil can benefit from top-dressing with organic matter.  Older  lawns can benefit from over-seeding with newer varieties of grass seed cultivated to be more resilient to Red Thread and other common lawn diseases.