Anthracnose Disease in Poa Grass

Causal Agent

• Anthracnose is a fungal disease affecting variety of turfgrass species throughout the world. The disease, caused by Colletotrichum cereale, is especially severe on poa grass, cites the Rutgers University Extension. Disease symptoms may persist throughout the year but are especially noticeable between June and September.

Symptoms

• The disease starts with the appearance of ¼ to ½ inch, round, yellow-to-orange brown lesions on grass. With disease progression, the spots get larger and irregularly shaped. Older grass blades show symptoms first. When the fungus moves into the leaf stems, sheaths and crown, the disease is called basal stem rot. Symptoms of basal stem rot include water-soaked lesions that rapidly turn black as tissues rot. The entire plant dies from infection. Closer inspection reveals the presence of black-colored, fungal fruiting bodies or spores within the infected areas.

Favorable Conditions

• Fungal growth is especially favored during humid and warm, midsummer weather. However, disease also occurs during cooler weather. Anthracnose is common in grass growing with excessive soil moisture and compacted soil. Poa grass with less vigorous growth, mowed at lower height or is drought stressed, is also more prone to infection. Grass that is not regularly dethatched has an increased chance of infection.

Management

• Since anthracnose is difficult to control once infection occurs, preventative measures are among the best control strategies. Keep the grass well fertilized and use adequate levels of nitrogen especially during summer. Raise the mowing height, as this reduces stress on the grass. Dethatching grass regularly improves aeration in roots. Chemical control options include the use of triadimefon, propiconazole or chlorothalonil. Fungicides work best when used as preventive treatment or during the early stages of infection.