What Is Wrong With My St. Augustine Grass?

Identification

• Brown patch disease is among the serious fungal disorders of St. Augustine grass. Also referred to as rhizoctonia blight, the disease is caused by Rhizoctonia solani, a soilborne pathogen. It is common in lawns growing in poorly drained soil, in 75- to 95-degree Fahrenheit temperature and high humidity.

Damage

• Initial symptoms of disease include the appearance of purple bordered, purplish-green patches on grass. With time the patches turn brown and tan. Close inspection reveals tan-colored, red-ringed lesions on grass blades. Dead grass blades have a brittle texture.

Control

• Keep grass in good health with adequate irrigation and fertilizer. Grow grass in well- drained soil, and aerate lawns regularly. Avoid watering during late afternoon or evening, as the grass does not dry properly and encourages fungal growth. Recommended fungicides include flutolanil, iprodione or myclobutanil.