Anthracnose

Causal Agents

Colletotrichum cereale

Hosts

• Annual bluegrass
• Creeping bentgrass

Symptoms & Signs

There are 2 types of anthracnose diseases of turfgrass, a foliar blight and a basal rot. Plant symptoms of anthracnose foliar blight appear as reddish‑brown lesions on leaves. On annual bluegrass, elongated, chlorotic leaf spots with black spore‑producing acervuli appear in the center. Older leaves affected by foliar blight may appear completely water‑soaked and, as the disease progresses, become necrotic with acervuli scattered across them.

The base of plants with basal rot appears brown to black and water‑soaked. Crowns become soft and rotted with small black acervuli present. Affected leaves look yellow to orange without visible lesions.

Under the microscope, acervuli show characteristic black setae (spines) protruding from the infection mat. Spores of C. cereale are crescent‑shaped with a distinctive “oil‑globule” in the center.

When Does it Happen?

Anthracnose is most common on annual bluegrass, although highly stressed creeping bentgrasses can also be infected by C. cereale. Favorable temperatures for anthracnose development appear to be more related to turfgrass growth than to pathogen growth. In South Carolina, the disease is most problematic during the summer when turfgrass is under significant heat stress. Additional stressors—such as ultra‑low mowing heights, excessive traffic, drought, low fertility, poor drainage, and thatch accumulation—further increase the risk of anthracnose.

Cultural Control

Research indicates that anthracnose is exacerbated on stressed turfgrass. Increasing mowing height above 0.125” where possible can help. Rolling or using plant growth regulators can maintain desired playing conditions while accommodating a higher mowing height. Provide adequate fertilization and perform tissue sampling to identify deficiencies. Spoon‑feeding nitrogen throughout the summer can supply sufficient fertility without stimulating excess growth. Routine sand topdressing (a heavy spring application of 400‑800 lbs per 1000 ft² followed by biweekly light topdressing of 100 lbs per 1000 ft²) and regular aerification help protect plant crowns and reduce disease severity.

Chemical Management

Preventative fungicide applications provide the best control of anthracnose foliar blight and basal rot. Ideally, a preventative program should begin before the onset of summer stress. C. cereale can rapidly develop fungicide resistance—with well‑documented resistance to benzimidazole and QoI fungicides—and emerging resistance to DMI fungicides. To slow resistance development, rotate fungicide classes between applications and consider tank‑mixing products.