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How to Manage Pests

UC Pest Management Guidelines


Turfgrass

Leaf Blotch

Pathogen: Bipolaris cynodontis

(Reviewed 9/09, updated 9/09)

In this Guideline:


DESCRIPTION OF THE DISEASE

Leaf blotch appears as tiny purplish to reddish spots that occur on leaf blades and leaf sheaths. Seedlings are very susceptible, but older plants rapidly become resistant. Affected seedlings wither, die, and turn brown. The roots and crowns of infected plants may develop small lesions and rot. The disease occurs in irregular patches that range in size from 2 inches to 3 feet across.

SUSCEPTIBLE TURFGRASSES

Leaf blotch is a disease of bermudagrass. The pathogen survives in infected bermudagrass plants and debris.

CONDITIONS FAVORING DISEASE

Leaf blotch damages young bermudagrass seedlings or adult plants that are weakened by factors such as excess thatch, nitrogen deficiency, and other unfavorable growing conditions. The disease attacks during cool, wet weather, with symptoms usually seen from late autumn to spring.

MANAGEMENT

Follow good management practices; fungicides are usually not necessary except in young turfgrass.

Cultural Control
Remove thatch at regular intervals and apply adequate nitrogen to help prevent the development of this disease. Manage leaf wetness by irrigating pre-dawn to early morning.

Treatment Decisions
Fungicides are primarily used in young turfgrass; established, healthy turfgrass is not usually damaged by this disease.

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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