Magnaporthiopsis poae
Summer Patch (Magnaporthiopsis poae) is a serious fungal disease affecting Kentucky Bluegrass, Fine Fescues, Annual Bluegrass. It triggers under root infection initiates in spring at soil temp >65°f; foliar wilt symptoms appear during hot summer stress (85°f–95°f). Symptom manifestation begins with roots turn dark brown to black and slough off; turf pulls up effortlessly from soil like a carpet. Curative control requires Preventative Azoxystrobin or Pyraclostrobin applied in spring when soil temp reaches 65°F at 2-inch depth.
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Curative treatment of Summer Patch requires strict adherence to statutory EPA product label directions. University extension trials demonstrate high efficacy with the following commercial chemistries:
Broad-spectrum systemic strobilurin (Azoxystrobin, FRAC 11) for curative and preventative control of turf fungi.
Check Price on Amazon →High-potency organophosphate (Dylox / Trichlorfon) curative halting subterranean insect damage within 24 hours.
Check Price on Amazon →Pathogen virulence operates strictly under the classic Plant Disease Triangle: infection requires an active pathogen inoculum, a genetically susceptible turfgrass host, and conducive microclimatic conditions (primarily prolonged leaf canopy moisture exceeding 10 consecutive hours combined with elevated rootzone humidity). Unmown or excessively dense turf stands impede airflow, creating an insulated stagnant microclimate where fungal spore germination accelerates.
When evaluating suspect turf patches, cross-examine rootzone integrity against foliar discoloration. True root-rot pathogens compromise subterranean anchoring, allowing turfgrass mats to be pulled up effortlessly with zero tensile resistance. In contrast, foliar blights damage leaf blades while leaving crown tissue and primary adventitious roots viable for regenerative recovery once fungicide active ingredients are introduced.
Cultural Protocol: Acidify rootzone using ammonium sulfate fertilizer; Summer Patch pathogen is suppressed at soil pH <6.0. Always avoid excess evening irrigation; irrigate early between 4:00 AM and 8:00 AM to allow rapid sun-drying of turf foliage. Keep cutting blades sharp to minimize ragged blade wounds through which fungal hyphae penetrate.
Chemical Protocol: Preventative Azoxystrobin or Pyraclostrobin applied in spring when soil temp reaches 65°F at 2-inch depth. Rotate active ingredients across different FRAC / IRAC mode-of-action groups (such as rotating Group 11 strobilurins with Group 3 triazoles) to prevent resistant fungal strains from dominating your lawn ecosystem.
Summer Patch is recognized by Yellowish-tan crescents and doughnut-shaped rings with green centers ("frog-eye" pattern). forming 6 inches to 2 feet rings.. Blade symptoms: Roots turn dark brown to black and slough off; turf pulls up effortlessly from soil like a carpet.
Primary susceptible hosts include Kentucky Bluegrass, Fine Fescues, Annual Bluegrass. Maintaining proper fertilization and irrigation reduces pathogen virulence.
Extension-recommended treatment: Preventative Azoxystrobin or Pyraclostrobin applied in spring when soil temp reaches 65°F at 2-inch depth. Active ingredient: Azoxystrobin (Group 11).
Acidify rootzone using ammonium sulfate fertilizer; Summer Patch pathogen is suppressed at soil pH <6.0.
