Agriculture: Turfgrass Pest Management Guidelines

Anthracnose

  • Colletotrichum graminicola
  • Description of the Disease

    There are two types of anthracnose symptoms, a basal rot that occurs in cool, wet weather in spring and early summer, and a foliar blight that occurs under periods of heat and water stress. The foliar blight is most common in California; the basal rot anthracnose has not been reported in California.

    For foliar blight symptoms, the older leaves are often attacked first, with reddish-brown to brown lesions that turn a pale tan color.

    For basal rot, dark infection mats are often visible on the lower leaf sheaths and diseased crowns are often black and necrotic. Leaves are often yellow-orange.

    In both cases, the fungus can produce fruiting structures (acervuli) that have fine black hair-like projections (setae) and are filled with small, crescent-shaped spores.

    Susceptible Turfgrasses

    Anthracnose is most severe on annual bluegrass, Poa annua; it also occurs on Kentucky bluegrass, P. pratensis. Other species are only rarely affected by this disease in California.

    Conditions Favoring Disease

    Basal rot anthracnose is favored by cool, wet conditions (50 to 60°F) while the foliar blight is favored by higher temperatures (80 to 95°F). Both basal rot and foliar anthracnose development are favored by low soil fertility, high compaction, and high soil salinity. Extended periods of leaf wetness contribute to the development of the disease, as do practices that cause mechanical damage to the turf (top dressing and verticutting).

    Management

    Anthracnose is best managed by proper cultural practices. Fungicides should be used primarily on golf course greens and other intensively managed turf.

    Cultural Control

    Apply adequately balanced nutrients as necessary, concentrating on potassium and phosphorus. On golf course greens, fertilize with low rates of nitrogen (0.1–0.2 lb/1000 sq. ft.) monthly, especially during late spring and through the summer. Avoid fertilizing during periods of high temperatures (over 80°F).

    Irrigate deeply and infrequently based on evapotranspiration needs of turfgrass. Allow leaves to dry between irrigations. Irrigate early in the morning rather than during late afternoon or evening. Lightly water (syringe) golf greens during the day to reduce heat and drought stress.

    Reduce compaction through mechanical aerification in fall and spring. Increase mowing heights to reduce stress on affected turf. Increase air movement and reduce shading by selective pruning of trees and landscape that block air movement or light the grass. Periodically irrigate golf course greens heavily to leach salts if salinity is a problem.

    Treatment Decisions

    Fungicides are most effective when used preventively. For areas where anthracnose is common, begin applications when the soil temperature rises above 65°F (mid to late spring) to reduce the severity of initial epidemics.

    Strains of the anthracnose pathogen resistant to both QoI (Group 11) and benzimidazole (Group 1) fungicides have been documented in California. If control by fungicides from either mode-of-action group has been ineffective in the past year, switch to a fungicide with a different group number or try tank mixing with a multi-site fungicide such as chlorothalanil.

    Repeated applications of fungicides with the same group number for summer patch control may contribute to the development of fungicide resistance in anthracnose because both diseases tend to occur at the same time in the season. Practice resistance management strategies for both diseases at the same time by alternating chemicals with different mode-of-action group numbers.

    Common name Amount per 1000 sq ft** 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. CHLOROTHALONIL
    (Daconil Action) Label rates 12 Until dry
    MODE-OF-ACTION GROUP NAME (NUMBER1): Multi-site contact (M5)
    C. MYCLOBUTANIL
    (Eagle 20EW) 1.2 fl oz/1000 sq ft 24 Until dry
    MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
    D. PROPICONAZOLE
    (Banner Maxx) 1–2 fl oz/1000 sq ft 12 Until dry
    MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
    E. THIOPHANATE-METHYL
    (Fungo Flo) Label rates 12 Until dry
    MODE-OF-ACTION GROUP NAME (NUMBER1): Methyl benzimidazole (1)
    F. TRIADIMEFON
    (Bayleton 50 Turf and Ornamental) Label rates 12 Until dry
    MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
    G. TRIFLOXYSTROBIN
    (Compass) Label rates 12 Until dry
    MODE-OF-ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
    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