Fungi in Zoysia Grasses

Disease Identification

• Zoysia grass is susceptible to fairy ring caused by the Agrocybe spp., Marasmius oreades or Lepiota spp. fungi, powdery mildew caused by Erysiphe graminis, and phythium blight caused by the Phythium fungi. The disorder is also commonly referred to as grease spot.

Symptoms

• Fairy ring is characterized by the appearance of dark green or brown circular bands on grass. The outer edge of the band may start to grow mushrooms, and inspection reveals the presence of threadlike, white fungal bodies under affected grass. A common symptom of powdery mildew is the growth of grayish, white mold on grass blades. Left untreated, the fungus soon creates large patches on lawn. Affected grass starts to yellow. Phythium blight infection causes the grass to start dying in small circles. With disease progression, the dead areas enlarge rapidly and start to merge together. Leaf blades often blacken, wither and turn somewhat greasy.

Favorable Conditions

• Turf with thick thatch and an accumulated layer of undecomposed organic material are most prone to fairy rings. Grass suffering with inadequate fertilizer also frequently display damage. Powdery mildew is common under high humidity and cool temperatures of 65 degrees Fahrenheit. The disease is frequently seen on grass growing in poorly ventilated areas or moist shade. The phythium blight fungi thrive in consistently moist soil and temperatures of 80 to 90 degrees Fahrenheit. Grass that is fertilized with high nitrogen fertilizer is also more prone to disorder.

Control

• To control symptoms of fairy ring, fertilize lawns with adequate nitrogen as this will help to increase the activity of beneficial organisms in soil. Dethatch grass regularly to improve water absorbency. Grow shade-tolerant grasses for shady areas to minimize powdery mildew. Fertilize and irrigate lawns according to growth requirements. Management for phythium blight includes regular irrigation and minimizing use of excessive nitrogen. Make sure grass is growing in well-drained and aerated soil.