Agriculture: Turfgrass Pest Management Guidelines

Melting Out

  • Drechslera poae
  • Description of the Disease

    Melting out causes circular to elongated purplish or brown spots with straw-colored centers on leaf blades, leaf sheaths, and stems. The leaf spots may be widespread throughout the lawn, indicating spread by windborne spores. Crowns and roots are frequently affected with a dark brown rot. The crown-infected plants are weakened and may die in hot, windy weather, resulting in a thinning out of the turf in scattered areas. The fungus survives on infected bluegrass plants or grass debris and may be seedborne.

    Susceptible Turfgrasses

    Kentucky bluegrass is highly susceptible to melting out. Many improved bluegrass selections are resistant, including: Adelphi, Bristol, Destiny, Eclipse, Enmundi, Glade, Ikone, Liberty, Majestic, Mona, P-104, Rugby, and Somerset.

    Conditions Favoring Disease

    Cool (50°to 75°F), moist conditions favor melting out. Symptoms first appear on shaded plants. Melting out is most severe on closely mowed turf and on turf with high nitrogen fertilization.

    Management

    To prevent the development of melting out, follow good management practices. Reduce shade, improve soil aeration and water drainage, and control thatch. Avoid dry spots and maintain as high a cutting height as feasible. Apply recommended rates of nitrogen fertilizers. Select resistant cultivars. With the use of resistant cultivars and other recommended cultural management practices, fungicides should not be necessary in most situations. For susceptible cultivars, treat at the onset of symptoms.

    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 80 WP, Dithane M-45) 4 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