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UC Pest Management Guidelines


Turfgrass seedling with leaf spot, caused by Bipolaris sp.

Turfgrass

Leaf Spot

Pathogen: Bipolaris sorokiniana

(Reviewed 9/09, updated 9/09)

In this Guideline:


DESCRIPTION OF THE DISEASE

Leaf spot occurs on leaf blades, sheaths, and stems as circular to elongated purplish or brown spots with brown colored centers and purplish to dark brown borders. Spots may be found on turfgrass leaves throughout the site, indicating spread by windborne spores. Crown and roots are frequently affected with a dark brown rot. Plants with crown infections are weakened and may die in hot, windy weather, resulting in a thinning out of the turf in scattered areas.

SUSCEPTIBLE TURFGRASSES

Bentgrasses, bluegrasses, fescues, and ryegrasses are susceptible to leaf spot. The fungus survives in infected grass plants or grass debris and may be seedborne. Spores are airborne.

CONDITIONS FAVORING DISEASE

The disease is favored by warm temperatures (70° to 90°F), high humidity, extended leaf wetness, and closely cropped turfgrass. It is more severe under high nitrogen fertilization.

MANAGEMENT

Follow good management practices to prevent the development of leaf spot. Fungicides are usually not warranted.

Cultural Control
Reduce shade and improve soil aeration and water drainage. Avoid dry spots, overfertilizing with nitrogen, and maintain as high a cutting height as possible. Avoid prolonged leaf wetness by irrigating in pre-dawn, or early morning hours. If possible, increase air movement.

Treatment Decisions
Leaf spot usually is not serious enough in California to warrant the use of fungicides although they may be used in areas where leaf spot is severe.

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. CAPTAN Captan  
  MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M4) 4 days until dry
 
C. CHLOROTHALONIL Daconil  
  MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M5) 12 until dry
 
D. FLUDIOXONIL Medallion  
  MODE OF ACTION GROUP NAME (NUMBER1): Phenylpyrrole (12) 12 until dry
 
E. IPRODIONE Chipco 26019  
  MODE OF ACTION GROUP NAME (NUMBER1): Dicarboximide (2) see label until dry
 
F. MANCOZEB Fore, Dithane M-45  
  MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M3) 24 until dry
  COMMENTS: Dithane M-45 registered for use on sod farms only.
 
G. MYCLOBUTANIL Eagle  
  MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3) 24 until dry
 
H. PROPICONAZOLE Banner Maxx  
  MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3) 24 until dry
 
I. THIOPHANATE-METHYL Fungo 50, T-Methyl E-Pro  
  MODE OF ACTION GROUP NAME (NUMBER1): Methyl benzimidazole (1) 12 until dry
 
J. TRIFLOXYSTROBIN Compass  
  MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) 12 until dry
 
K. VINCLOZOLIN Curalan, Touche  
  MODE OF ACTION GROUP NAME (NUMBER1): Dicarboximide (2) 5 days 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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