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Understanding Large Patch Disease and its Effects on Florida Turfgrasses - Sit Down with CEPRA
Florida's warm, humid climate provides an ideal environment for lush, green lawns, but it also fosters conditions for turfgrass diseases such as Large Patch. This fungal disease, caused by Rhizoctonia solani, is a significant disease to many turfgrass species commonly grown in the state, including St. Augustine and Zoysia. Recognizing the symptoms and understanding how the disease develops can help turf grass managers effectively manage and prevent its spread.
Large Patch in St. Augustine
Large Patch in Zoysia
What is Large Patch?
Large Patch is a fungal disease that primarily affects warm-season turf grasses. It becomes active during cooler, moist conditions, typically in the fall, winter and spring when soil temperatures range between 60- and 70-degree Fahrenheit. While the disease remains dormant during the hot summer months, the fungus survives in the soil waiting for favorable conditions to resume activity.
The development of Large Patch is closely related to environmental factors and cultural practices:
- Temperature and Moisture: This disease thrives in cool damp conditions. Excessive rainfall and over irrigation during cooler months can create the moist environment needed for the fungus to grow and spread.
- Susceptible Grass: Warm season turf grasses are particularly vulnerable, especially when they are transitioning into dormancy in the fall or breaking dormancy in the spring.
- Poor Drainage & Thatch Accumulation: Compacted soils, poor drainage and a think layer of thatch can exacerbate the disease by retaining moisture and providing the fungus with a favorable habitat.
- Improper Fertilization: Over fertilization, especially with nitrogen, during the cooler months can stimulate tender grass growth that is more susceptible to infection.
Symptoms of Large Patch:
- Yellowing or Bronzing: The grass in the affected area often turns yellow or bronze.
- Thinning of Turf: Infected patches become thin and may develop a sunken appearance.
- Leaf Sheath Rot: The base of the affected leaf sheaths appears brown and slimy when examined closely.
Effective management of Large Patch involves a combination of cultural practices and if necessary chemical treatments.
Sheath Rot in St Augustine
Cultural Practices:
- Water Wisely: Avoid overwatering especially during cooler months. If possible, water only in the early morning to allow grass to dry quickly.
- Improve Drainage: Aerate compacted soils and address drainage issues to reduce moisture retention.
- Fertilization Timing: Apply fertilizer with quick release nitrogen inputs during the active growing season rather than in cooler months.
Chemical Control
Fungicides can be effective in controlling Large Patch if applied preventatively or at the first signs of disease. Products containing azoxystrobin, flutolanil or propiconazole are commonly recommended. Follow label instructions carefully for the best results.
Conclusion
Large Patch is a persistent problem for Florida's warm season turf grasses, but understanding its life cycle and environmental triggers can help in managing the disease. By adopting proper lawn care practices and staying vigilant for early symptoms, you can protect your turf grass from severe damage and maintain a healthy, vibrant lawn year-round.