Summer patch is a common disease of Kentucky bluegrass and creeping red fescue lawns. The following are some control guidelines.
Now is the time to initiate an effective chemical and cultural control program for summer patch. This disease of Kentucky bluegrass and creeping red fescue is caused by the fungus Magnaporthe poae and can be controlled through the use of good cultural practices and the application of a penetrant fungicide. For best results, maintain soil pH at or slightly below 6.0, fertilize turf with ammonium sulfate (during cool weather to avoid phytotoxicity) or sulfur-coated urea, avoid the use of nitrate-based fertilizers (which can enhance symptom severity), and aerify (before symptoms develop) to reduce compaction and decrease disease severity. Fungicides are most effective when applied in mid- to late-May (i.e., when the soil temperatures at a 2 inch depth exceed 65 0 F for 5 to 6 consecutive days) and then repeated two additional times at 28 day intervals. To optimize control, apply Armada, Banner, Bayleton, Compass, Disarm, Eagle, Headway, Heritage, Insignia, Rubigan, Tartan, thiophanate- methyl or Trinity in 4 to 5 gal water/1000 ft. If products are delivered in lower water volumes (e.g., 2 gal water/1000 ft2), irrigate with 1/8 inch of water immediately following application to enhance disease control.
Reprinted in part from "Diseases of Turfgrass" by Bruce B. Clarke, Ph.D., Specialist in Turfgrass Pathology in the May 28, 2009 edition of the Plant and Pest Advisory newsletter, Landscape, Nursery and Turf Edition from Rutgers University.