Anthracnose is one of the most destructive foliar diseases affecting golf greens, capable of causing significant aesthetic damage and playability issues during the warm months of the year. Caused primarily by the fungal pathogen Colletotrichum graminicola, this disease thrives in the high-moisture, warm-temperature conditions that are typical of summer stress on turfgrass. For superintendents and greenkeepers, understanding the intricacies of anthracnose is essential for implementing effective prevention strategies and maintaining premium putting surfaces.
Understanding the Pathogen and Infection Cycle
The lifecycle of Colletotrichum graminicola is the foundation of effective disease management. This fungus survives the winter not only in infected plant debris but also as dormant mycelium within the living leaf tissue of the grass. As temperatures rise in the spring, the pathogen becomes active, and the primary inoculum is spread across the green via water splash, mowing equipment, and foot traffic. The infection process is particularly efficient when the leaf surface is wet for extended periods, allowing the spores to germinate and penetrate the grass blades through natural openings or direct penetration.
Identifying Symptoms on Golf Greens
Early detection is critical for minimizing the impact of anthracnose, and visual identification is the first step in the process. Initial symptoms often appear as small, water-soaked lesions that rapidly expand into distinct tan to straw-colored spots. A key diagnostic feature is the appearance of tiny black fungal fruiting bodies, known as acervuli, within the lesions, which gives the affected tissue a distinctly speckled appearance. In severe cases, the disease can progress to "blighting," where large sections of the green turn brown and die, often following a pattern of circular or irregular patches that can be mistaken for drought stress or chemical burn.
Distinguishing from Other Diseases
Misdiagnosis is a common pitfall in managing turf diseases, as symptoms of anthracnose can closely resemble those of dollar spot or even physical damage from heavy play. Unlike dollar spot, which typically presents with small, circular, bleached spots and a distinct reddish-brown hue around the perimeter, anthracnose lesions are generally more irregular and lack the pronounced straw-colored hue. Furthermore, while dollar spot often occurs in areas of low fertility, anthracnose is frequently exacerbated by high nitrogen fertility during the peak growing season, making the visual distinction between these two ailments a vital skill for any greens manager.
Cultural Control Strategies
Long-term management of anthracnose relies heavily on cultural practices that reduce the environment's suitability for the pathogen. Since the disease requires free water to infect and spread, implementing strategies to minimize leaf wetness is paramount. This includes scheduling irrigation early in the morning to allow surfaces to dry quickly and avoiding late afternoon watering sessions. Additionally, careful management of nitrogen fertility is crucial; while greens require adequate nutrition, excessive nitrogen can create lush, succulent growth that is highly susceptible to infection. A balanced fertility program that maintains color without promoting excessive growth is the cornerstone of an effective cultural program.
Improve Air Circulation: Prune surrounding vegetation and avoid planting turfgrass too densely to promote drying.
Implement Thatch Management: Dethatch regularly to reduce the habitat where the fungus can survive and ensure water infiltration.
Mower Hygiene: Sterilize mowing equipment between greens and during outbreaks to prevent the mechanical spread of the pathogen.
Height of Cut: Maintain slightly higher mowing heights during stress periods to protect the crown tissue and encourage recovery.
