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Welcome to The Turf Zone podcast. This episode covers how timing matters in correctly identifying large patch and brown patch. Written by Nar B. Ranabhat, Assistant Professor and Extension Plant Pathologist, University of Tennessee.

Large patch and brown patch can look similar, but they require different management strategies especially when it comes to fungicide application timing. Correctly identifying the disease, scouting at the right time, and applying fungicides when needed can help improve the turfgrass health.

Disease

Large patch and brown patch are fungal diseases caused by different strains of Rhizoctonia solani. Large patch mainly affects warm-season grasses including zoysiagrass, bermudagrass, centipedegrass, and St. Augustinegrass. Activity of this R. solani strain is most active during cool and wet weather in fall and spring, when temperatures range from 50°F to 70°F.

Brown patch primarily affects cool season turfgrass, especially tall fescue. This is the most damaging pathogen of tall fescue throughout Tennessee particularly in middle and east Tennessee. Activity of this R. solani strain is most common during warm, humid weather, when temperatures range from 70°F to 90°F.

Scouting Time

Start scouting for large patch in the fall during when soil temperatures approach near 70°F. Watch for brown patch from late spring through summer, especially during hot and humid weather. Since both diseases often return to the same spots, keep a close eye on areas that have had problems before.

Fungicide Application Timing

Timing is critical for effective disease management. For large patch, apply preventive fungicides in the fall before turfgrass goes dormant, rather than waiting until large patches are visible.

For brown patch, consider fungicide applications before or as warm, humid summer conditions begin, especially in areas with a history of disease. The goal is to protect healthy turf before the disease becomes severe, not simply to treat visible symptoms after they appear.

Can Nitrogen Management Affect Large patch and Brown patch development?

Fungicides are an important tool for managing severe turf disease outbreaks, but they are only one part of an effective disease management program. What happens day to day on the turf field can have just as much impact, and nitrogen management is an important part of those practices.

Applying too much nitrogen during periods when turfgrass is most vulnerable can increase the risk and severity of large and brown patches. For warm season turfgrass, avoid excess nitrogen applications in late fall and early spring, when large patch risk is highest. For cool season turfgrass, avoid excess nitrogen application during hot, humid summer, when brown patch risk is highest.

The goal is not to avoid nitrogen, but to apply the right amount at the right time. A well balanced nitrogen program can help reduce the conditions that favor disease development.

What Else Should I Do Besides Spraying?

• Other cultural practices also help reduce disease pressure and keep turf healthy.
• Improve drainage and air circulation when possible.
• Reduce the prolonged leaf wetness.
• Water carefully and avoid unnecessary nighttime irrigation.
• Manage thatch and avoid practices that place extra stress on the turf.
• Scout regularly and use past disease problems to guide management decisions.

Key Takeaways

For Tennessee turfgrass professionals, the main difference in managing Large Patch and Brown Patch is timing for scouting and management actions:

• Large patch affects warm-season turf and is best managed with fall scouting and preventive treatments.
• Brown patch affects cool-season turf and requires scouting and preventive treatment during the summer.

Accurate diagnosis, timely application, and good cultural practices can improve disease control and help make fungicide use more targeted and effective.

For more information about the disease and lists of fungicide products, see the Extension publication: “Large Path vs. Brown Patch in Turfgrass: How to tell the Difference” by Nar B. Ranabhat and Becky Bowling.

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