Field Insights Blog | GreenCast | Syngenta
Field Insights Blog | GreenCast | Syngenta

Large patch: Confusion clarified

The arrival of fall brings vivid colors clarity to the season.  From the deep blue skies to the changing colors of tree leaves to the vivid green color of golf course turf the clarity of the season is on full display.  Against this background, a confusing and opaque turf disease both its cause and name occurs.

Photograph 1.  Symptoms of large patch on St. Augustinegrass.

Large patch is a disease that occurs in the fall on warm season turfgrass areas in the southeastern and southwestern United States.  Formerly known by the names like zoysia patch and brown patch, large patch brings clarity to a confusing nomenclature.  Large patch attacks the warm-season turfgrasses seashore paspalum, centipedegrass, zoysiagrass, and St. Augustinegrass.  Bermudagrass is the least susceptible of the warm-season turfgrass mentioned.  

Fall symptoms can appear as roughly circular patches, slightly matted areas of bright orange, and discolored turfgrass. Individual shoots within the patch develop pinpoint, reddish-brown to black lesions on the basal leaf sheaths.  The leaves in the patch turn white or bleach-out.  The patches range in size but can reach several feet or yards in diameter,  The symptoms are most obvious when warm season turfgrasses like zoysiagrass begin to enter winter dormancy

Photograph: Large patch symptom across a zoysiagrass fairway and rough.

Large patch is caused by the fungal pathogen Rhizoctonia solani.  For those familiar with managing cool-season turfgrasses like creeping bentgrass, annual bluegrass, and tall fescue Rhizoctinia solani causes brown patch.  Rhizoctonia solani that causes large patch is a different strain than the strain that causes brown patch.  Specifically the strain for large patch is described as Rhizoctonia solani AG 2-2 (LP) while the pathogen for brown patch is Rhizoctonia solani AG 1-A.

Photograph 3.  Large patch symptoms on centipedegrass.

The two different strains of Rhizoctonia solani accounts for the difference in the type of turfgrass species infected and the conditions under which infect and symptoms are expressed.   Large patch becomes active when temperatures remain above 50 °F and ceases once temperatures reach into the mid 80s.  Combined with wet conditions, large patch is most prevalent when warm season turfgrasses are slowing growth fall growth as they enter winter dormancy.

Large patch management and control practices are pretty clear.  Practices that help reduce the severity of large patch include using, where appropriate, resistant or more tolerant warm season turfgrass species.  Bermudagrass is rather tolerant to large patch, and recovers quickly from infection. During the fall avoid nitrogen fertilization when turfgrass growth is slowing. Reduce any excessive thatch accumulation. Severity of large patch increases with increasing amounts of thatch.  Stressful conditions like lower mowing heights, and  where wear injury occurs should be alleviated.

Photograph:  Large patch symptoms on a zoysiagrass golf tee.

Fungicides like azoxystrobin (ex. Heritage® TL) and azoxystrobin combination products (ex. Heritage Action, Posterity® ForteRenown®, Headway®)  are effective for controlling large patch.  Preventative applications targeted when soil temperatures are in the 70 to 80 °F range are effective.

Syngenta introduced Ascernity® fungicide 
earlier this year. Ascernity is now the cornerstone of the updated GreenTrust® 365 Large Patch Assurance Program.

To assist you in timing for your applications, be sure to sign up for Large Patch Alerts from Syngenta. 

For more information on Large Patch, be sure to read Lane Tredway's article on Large Patch here

About the author

Dr. Karl Danneberger is a professor of Turfgrass Science at The Ohio State University. Dr. Danneberger's contact information can be found here. You may also follow Dr. Danneberger on Twitter:

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