Anthracnose
Causal Fungus: Colletotrichum cereale
Host Grass: Common Bermuda, Buffalo Grass, St. Augustine Grass(Stenatophrum secundatum)
Cause and Symptoms: The visible symptoms of anthracnose on turf are variable. Typically, it is recognized by damaged turf in a pattern of dots, circles, or irregularly shaped patches ranging in size from several inches to many feet in diameter (Figure 1). The overall color of affected turfgrass can go from orange to reddish brown to tan. The fungal disease also causes a foliar blight or a basal rot of individual plants. Occasionally, reddish brown spots on leaves are produced at the early infection, which then turn yellow and finally light tan or brown as the plants die. In a worst-case scenario, the basal rotting affects crown and root systems, yellowing and killing the whole plant.
Figure 1. Anthracnose produces a yellowing of leaves.
Grayish black mycelial mats are observed on lower sheath and stems. Tiny black fruiting bodies known as acervuli form on dead leaves or stems (Figure 2). These microscopic structural features are a key sign for diagnosing anthracnose.
Control and Management:
Key cultural practices that reduce the occurrence and severity of the disease include:
- Provide proper fertility
- Alleviate soil compaction
- Avoid excessive traffic
- Maintain adequate soil moisture
In most cases, anthracnose outbreaks are associated with stressed plants from abiotic factors such as improper watering, inadequate supplies of nutrients, and soil compaction. Therefore, proper cultural practices remediating these stress factors are important as a preventative management practice for this disease.
Do not apply high rates of nitrogen during periods of drought or high temperatures. Make sure to use slow-release and balanced fertilizers for turfgrass infected by anthracnose. Water turf deeply but as seldom as possible to avoid stressful conditions for turfgrass and discourage fungal infection. Avoid watering during the late afternoon or evening to shorten leaf wetness. Raising mowing heights will alleviate stress on turfgrass as mowing to low tends to increase the severity of the disease. Topdressing, aerification, vertical mowing and any other cultural practices that use equipment that can be abrasive to turfgrass can increase severity of this disease. Be careful when doing such treatments or try to avoid them as much as possible, especially when the disease is active.
Although fungicides hasten recovery of affected turf, anthracnose has shown evidence of increased resistance against some fungicides. Therefore, alternating between different fungicide groups and not using a single product are recommended for chemical management. Preventative fungicide applications along with proper cultural practices are widely considered best for the sustainable management of anthracnose.
Figure 2. Acervuli is fruiting bodies of the fungus, having characteristic protruding black hairlike structure. Ascervuli are found on leaves, sheaths, or stems of infected turfgrass.
Content edited by:
Young-Ki Jo (ykjo@tamu.edu, Professor and Extension Specialist)
Raleigh Darnell and Paul Goetze (Extension Assistant)
Department of Plant Pathology & Microbiology, Texas A&M AgriLife Extension Service
September 31, 2021
