Agriculture: Turfgrass Pest Management Guidelines

Leaf Blotch

  • Bipolaris cynodontis
  • 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 Amount to use Ag Use
    REI‡
    NonAg Use
    REI‡
    (Example trade name) (hours) (hours)
    Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least likely to cause resistance are at the top of the table. When choosing a pesticide, consider information relating to the pesticide's properties and application timing, honey bees, and environmental impact. Always read the label of the product being used.
     
    A. AZOXYSTROBIN
      (Heritage) 0.2–0.4 oz/1000 sq ft 4 Until dry
      MODE-OF-ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
     
    B. CAPTAN
      (Captan 4L or 50 WP) Label rates See label Until dry
      MODE-OF-ACTION GROUP NAME (NUMBER1): Multi-site contact (M4)
     
    C. CHLOROTHALONIL
      (Daconil Action) Label rates 12 Until dry
      MODE-OF-ACTION GROUP NAME (NUMBER1): Multi-site contact (M5)
     
    D. FLUDIOXONIL
      (Medallion) 0.25–0.5 oz/1000 sq ft 12 Until dry
      MODE-OF-ACTION GROUP NAME (NUMBER1): Phenylpyrrole (12)
     
    E. IPRODIONE
      (Chipco 26019) 3–4 fl oz/1000 sq ft See label Until dry
      MODE-OF-ACTION GROUP NAME (NUMBER1): Dicarboximide (2)
     
    F. MANCOZEB
      (Fore 80WP) 4–8 oz/1000 sq ft 24 Until dry
      MODE-OF-ACTION GROUP NAME (NUMBER1): Multi-site contact (M3)
      COMMENTS: Dithane M-45 registered for use on sod farms only.
     
    G. MYCLOBUTANIL
      (Eagle 20EW) 1.2 fl oz/1000 sq ft 24 Until dry
      MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
     
    H. PROPICONAZOLE
      (Banner Maxx) 1–2 fl oz/1000 sq ft 12 Until dry
      MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
     
    I. THIOPHANATE-METHYL
      (Fungo Flo) Label rates 12 Until dry
      MODE-OF-ACTION GROUP NAME (NUMBER1): Methyl benzimidazole (1)
     
    J. TRIFLOXYSTROBIN
      (Compass) Label rates 12 Until dry
      MODE-OF-ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
     
    K. VINCLOZOLIN
      (Curalan EG, Touche EG) 2.7 lb/acre (1 oz/1000 sq ft) 120 (5 days) Until dry
      MODE-OF-ACTION GROUP NAME (NUMBER1): Dicarboximide (2)
    1 Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of action. 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 a 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.
    Text Updated: 09/09
    Treatment Table Updated: 12/16