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Red Thread and Pink Patch in Cool-season Lawns

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This podcast details the identification and control alternatives for two important spring lawn diseases (Red Thread and/or Pink Patch).  The brightly colored fungal threads that appear on the turf during persistent cool, wet conditions generate a lot of attention by both homeowners and lawn care professionals alike.

Spring-like temperatures and plenty of moisture result in ideal conditions for some of the mid-Atlantic region’s most common turfgrass diseases to make an appearance in  lawns, particularly cool-season grasses such as Kentucky bluegrass and perennial ryegrass.  The disease present is likely one of two things, both diseases having quite descriptive names that make them easy to identify based on their symptoms (i.e. appearance):  Red thread or Pink patch.   The bright red to pink mycelial growth of this fungus is plainly visible early in the morning, particularly when the dew is still on the grass.  The disease will remain an eyesore as long as cool, moist periods persist, but the fungus only attacks the foliage and rarely will the entire plant die.  

What should you do to manage this disease?  Almost always, the proper treatment is to leave it alone rather than applying a fungicide.  As the weather warms and dries,  red thread and pink patch will gradually disappear.  While not always the case, these diseases are often associated with a nitrogen deficiency.  If your cool-season lawn has already received 1 to 1.5 lbs N/1000 sq ft in the spring, don’t apply any more N.  However, if the lawn is truly hungry from lack of N, then feeding it appropriately (making an application of no more than 0.5 to 1 lb N/1000 sq ft) will promote turf recovery.

If the disease is serious enough to warrant treatment (as judged by either the homeowner or a lawn care professional) there are some specific fungicides that provide exceptional control.  Some of the chemicals noted by VT Turf Pathologist David McCall as doing exceptionally well in the Virginia Tech field trials are Prostar (flutolanil), Heritage (azoxystrobin), and Armada (a combination product containing trifloxystrobin, the active ingredient of ‘Compass’ and triadimefon, the active ingredient of ‘Bayleton’).    There are several more fungicides that provide control that can be found in the current Virginia Tech Pest Management Guide.