Fungus on My St. Augustine Grass in Florida

Types

• Gray leaf spot is caused by the fungus Pyricularia grisea and is damaging in warm, rainy weather. According to the University of Florida, IFAS Extension, St. Augustine grass is the only warm season turfgrass affected by gray leaf spot. Take-all root rot is another disease of St. Augustine grass, as well as many warm season turfgrasses. Wet conditions, which are common in the summer and fall months in Florida, favor disease development.

Symptoms

• Gray leaf spot causes brown spots on grass with a light gray center. Spots grow rapidly and have a water-soaked appearance. This disease reduces grass vigor and causes thinning of St. Augustine grass. Take-all root rot does not affect grass blades, but attacks grass roots. Above-ground symptoms include yellow grass with patches of light green. Roots turn white, developing black lesions and grass becomes very thin.

Control

• Reducing drought stress on St. Augustine grass is accomplished with irrigation. Applying fungicides reduces the effects of fungal diseases and is most effective when used as a preventative before symptoms are severe.