How to Manage Pests

UC Pest Management Guidelines


Summer Patch

Pathogen: Magnaporthe poae

(Reviewed 9/09, updated 9/09, pesticides updated 12/16)

In this Guideline:


Summer patch appears as circular yellow or tan areas up to 1 foot in diameter, consisting of dead and dying plants. Roots, crowns, and stolons are affected by a dark brown rot. Young roots may appear healthy, although dark brown hyphae may be present on these tissues. Vascular discoloration and cortical rot occur in later stages of the disease. On occasion, patches may retain centers of green, apparently unaffected grass. The fungus can survive as mycelia in plant debris or in host tissue.


This disease has been reported on red fescue, Chewing's fescue, hard fescue, perennial ryegrass, and creeping bentgrass, but appears to be most destructive to annual bluegrass and Kentucky bluegrass.


Infections occur when soil temperatures are consistently at 65° to 70°F, and symptoms tend to appear when air temperatures are 83°to 95°F or higher. The disease is most severe on closely mowed turf (e.g. golf greens) with heavy irrigation or high soil moisture.


Follow good cultural practices to prevent the development of summer patch. Fungicides may be required for control if summer patch has been a problem in previous years.

Cultural Control

Promote root growth by soil aeration and slow-release nitrogen. Improve drainage, reduce compaction and mechanical damage or traffic, control thatch, and avoid drought stress. Irrigate based on evapotranspiration needs of turfgrass. Do not set mowing height lower than necessary. Lightly water (syringe) turf during periods of hot weather to reduce heat stress.

In areas where summer patch is frequent, begin fungicide applications when soil temperatures begin to be consistently in the 65° to 70°F range. This may be 3 to 4 weeks before symptoms are typically seen. Apply fungicides in a water volume equivalent to about 2 to 4 gal/1000 sq. ft. of water in fungicides to ensure materials reach the root zone. Fungicide applications made after strong symptom expression are generally ineffective.

Repeated applications of fungicides from the same chemical class for summer patch control may contribute to the development of fungicide resistance in anthracnose for the benzimidazole, DMI, and QoI (strobilurins) fungicides because the diseases tend to occur during the same period.

Common name Amount to use Ag Use
NonAg Use
(Example trade name)   (hours) (days)

UPDATED: 12/16
Calculate impact of pesticide on air quality
Bee precaution pesticide ratings
When choosing a pesticide, consider its usefulness in an IPM program by reviewing the pesticide's properties, efficacy, application timing, and information relating to resistance management, honey bees (PDF), and environmental impact. Not all registered pesticides are listed. Always read the label of the product being used.
  (Heritage) 0.2–0.4 oz/1000 sq ft 4 Until dry
  MODE-OF-ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
  (Medallion) 0.5 oz/1000 sq ft 12 Until dry
  MODE-OF-ACTION GROUP NAME (NUMBER1): Phenylpyrrole (12)
  (Eagle 20EW) 1.2–2.4 fl oz/1000 sq ft 24 Until dry
  MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
  (Banner Maxx) Label Rates 12 Until dry
  MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
  (Fungo Flo) Label rates 12 Until dry
  MODE-OF-ACTION GROUP NAME (NUMBER1): Methyl benzimidazole (1)
  (Bayleton 50 Turf and Ornamental) Label rates 12 Until dry
  MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
  (Compass) Label rates 12 Until dry
  MODE-OF-ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
1 Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of actions. Fungicides with a different group number are suitable to alternate in a resistance management program. In California, make no more than one application of fungicides with mode-of-action group numbers 1, 4, 9, 11, or 17 before rotating to a fungicide with a different mode-of-action group number; for fungicides with other group numbers, make no more than two consecutive applications before rotating to fungicide with a different mode-of-action group number.
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Agricultural use applies to sod farms and commercial seed production.



[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Turfgrass
UC ANR Publication 3365-T


A. Downer, UC Cooperative Extension, Ventura County
M. A. Harivandi, UC Cooperative Extension, Alameda County

Acknowledgment for contributions to Diseases:
F. Wong, Plant Pathology, UC Riverside
J. Hartin, UC Cooperative Extension, San Bernardino County
M. E. Grebus, Plant Pathology, UC Riverside

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