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How to Manage Pests

UC Pest Management Guidelines


Turfgrass

Summer Patch

Pathogen: Magnaporthe poae

(Reviewed 9/09, updated 9/09)

In this Guideline:


DESCRIPTION OF THE DISEASE

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.

SUSCEPTIBLE TURFGRASSES

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.

CONDITIONS FAVORING DISEASE

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.

MANAGEMENT

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.

Treatment Decisions
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 Example trade names Ag Use
R.E.I.+
NonAg Use
R.E.I.+
(trade name)   (hours) (hours)

  Calculate impact of pesticide on air quality
When choosing a fungicide, consider general properties as well as information relating to environmental impact.
 
A. AZOXYSTROBIN Heritage  
  MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) 4 until dry
 
B. FENARIMOL Rubigan  
  MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3) 12 until dry
  COMMENTS: Use with caution on bluegrass species.
 
C. FLUDIOXONIL Medallion  
  MODE OF ACTION GROUP NAME (NUMBER1): Phenylpyrrole (12) 12 until dry
 
D. MYCLOBUTANIL Eagle  
  MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3) 24 until dry
 
E. PROPICONAZOLE Banner Maxx  
  MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3) 24 until dry
 
F. THIOPHANATE-METHYL Fungo 50, T-Methyl E-Pro  
  MODE OF ACTION GROUP NAME (NUMBER1): Methyl benzimidazole (1) 12 until dry
 
G. TRIADIMEFON Bayleton  
  MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3) 12 until dry
 
H. TRIFLOXYSTROBIN Compass  
  MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) 12 until dry
 
1 Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of actions (for more information, see http://www.frac.info/). 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 (R.E.I.) 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.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Turfgrass
UC ANR Publication 3365-T
Diseases
F. Wong, Plant Pathology, UC Riverside
M. A. Harivandi, UC Cooperative Extension, Alameda County
Acknowledgment for contributions to Diseases:
J. Hartin, UC Cooperative Extension, San Bernardino County
M. E. Grebus, Plant Pathology, UC Riverside

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