Recent periods of warm temperatures, high humidity, and frequent rainfall across Georgia have created favorable conditions for the development of Pythium blight in tall fescue. This destructive disease, caused by several species of Pythium, can spread rapidly under conducive environmental conditions and result in significant turf loss within a short period of time.
Initial symptoms typically appear as small, irregularly shaped patches of dark green, water-soaked turf. As the disease progresses, affected leaves collapse, become matted, and develop an oily or greasy appearance before rapidly turning brown and dying. Under conditions of high humidity and prolonged leaf wetness, white, cottony mycelial growth may be observed on infected turf during the early morning hours.
Pythium blight is most severe during periods of hot, wet weather when daytime temperatures exceed 85°F and nighttime temperatures remain above 68°F. Excessive soil moisture, poor air circulation, prolonged leaf wetness, and high nitrogen fertility further increase disease risk and turf stress.
An integrated management approach is essential for minimizing disease severity. Cultural practices should include avoiding nitrogen fertilizer applications during active disease outbreaks, promoting adequate drainage, allowing foliage to dry between irrigation events, increasing air movement, reducing excessive thatch and organic matter through cultivation practices, and maintaining proper mowing height for tall fescue.
Accurate diagnosis is critical because effective management of Pythium blight requires fungicides with activity against oomycetes. Fungicides containing active ingredients such as mefenoxam (Subdue MAXX®), cyazofamid (Segway®), and other labeled products can provide effective control when applied according to label directions. Consult the2026 Georgia Pest Management Handbookand the2026 Turfgrass Pest Control Recommendations for Professionalsfor curren t fungicide recommendations, application rates, and resistance management guidelines. Always, carefully read and follow all pesticide label instructions and implement best management practices to maximize disease control.
