Summer Patch on Golf Courses

Summer patch caused by the pathogen Magnaporthe poae colonizes cool-season turfgrassses specifically Kentucky bluegrass and annual bluegrss (Poa annua L.). roots during spring and early summer.  Symptoms however do not show until later in the summer.  Upon arrival of hot dry weather, the root systems dieback and become dysfunctional.  


Photograph 1.  Summer patch symptoms on a Kentucky bluegrass turf.  Symptoms have a "frog-eye" appearance.

Symptoms appear as irregular shaped patches, rings or crescents when temperatures rise (85 - 95°F).  Symptom expression is most severe when wet conditions are followed by dry or droughty conditions.  Disease symptoms are chronic, appearing in the same locations year after year.  A sign of summer patch is weed colonization within the dying centers of the patches.  The most common weed types are dandelion, crabgrass and plaintain.


Photograph 2.  Summer patch occurs globally as long as a susceptible host is present.  In this case, it was Kentucky bluegrass.

Cultural management practices can help reduce the severity of summer patch including relieving soil compaction, providing adequate fertility, and planting where applicable resistant Kentucky bluegrass cultivars.  Some cultivars of Kentucky bluegrass have shown tolerance to summer patch. In some instances, overseeding summer patch  areas with perennial ryegrass or tall fescue reduces disease occurrance.  Both perennial ryegrass and tall fescue are highly tolerant to summer patch.


Photograph 3.  Summer patch is a severe disease on annual bluegrass turf.  Here the yellowish outer border of summer patch is present.  Frequently creeping bentgrass colonizes the inner portion of the diseased oatch.

Drought stress increases the severity of summer patch, thus proper watering is important.  Minimize drought or wilt injury through frequent (syringing) applications of water.  The lack of a functional root system limits the amount of water taken up by the troot system.


Photograph 4. Summer patch symptoms on an annual bluegrass green.

Additional practices like moderate applications of nitrogen should be made that promotes healthy growth but not excessive production of leaf tissue.  Practices to reduce soil compaction have been found to reduce the severity of summer patch.

Chemical Control

Fungicide applications reduce the severity of summer patch, but do not eradicate the problem. Timing is critical in fungicide applications. The best approach is to treat preventatively with an application made in spring when soil temperatures reach and remain above 65 °F at the two to three inch level. A second application is made one month following the initial recommendation. Given that the pathogen attacks the roots, the fungicide should be applied in four to five gallons of water per 1,000 square feet and watered in following application.  

Suggested fungicides to combat summer patch include Briskway^®, Heritage^® Action™ or Posterity^® XT  For specific fungicide recommendations, you can view the Efficacy Chart on the following Disease ID Guide from Syngenta.