Red thread, pink patch, and dollar spot in lawns and roughs – Turfgrass Science at Purdue University

Red thread, pink patch, and dollar spot in lawns and roughs

Red thread and its close relative pink patch, are now appearing on home lawns (and golf course roughs) in the central and southern parts of Indiana. Red thread first appears as small (quarter to golf ball size) gray – tan colored patches in the turf. After extended dew periods, white – pink mold may be evident within the affected turf. Under favorable environmental conditions, radial growth of the mycelium (mold) will allow the patches to expand to 8″ or more in diameter. Upon close inspection, characteristic red to coral colored “threads” (sclerotia) are often seen growing from tips of infected leaves. Pink patch produces nearly identical symptoms, but the pathogen does not produce the characteristic ‘red thread’ sclerotia. With the warming weather and wet soils, we expect dollar spot to go on a rampage very soon. This disease first appears as small (1″ diameter) patches of thin turf with bleached or straw-colored leaf blades within the patch. Careful inspection of affected turf may reveal distinct light tan lesions on grass blades. The lesions often have an hourglass shape with reddish brown margins. Fluffy white mycelium may be evident within the patches during early morning hours, after long periods of dew. The occurrence of any of these diseases indicates that the turf stand is nitrogen-starved. All three of these diseases are more common under low fertility. The traditional May or early June fertilization on lawns, athletic fields, and golf courses should help to minimize these diseases. If you have a problem with these diseases and have not fertilized in the last few months, apply 0.75-1.0 lb N/1000 sq. ft. with primarily slow release N. These diseases are most common on perennial ryegrass lawns, so avoid more than 10% perennial ryegrass in a seed mix when seeding a new turf area. Though fungicides easily control all these diseases, chemical applications normally are not necessary and generally not recommended on home lawns. More information can be found in Managing Lawn Diseases at http://www.agry.purdue.edu/turf/publicat.htm.


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