Owning or caring for a tall fescue lawn? Bentgrass green in the golf course? Then it’s time to scout for Brown patch (caused by Rhizoctonia solani) and Pythium blight (caused by Pythium spp). These diseases are often the most serious diseases on cool season grasses, especially on tall fescue, bentgrass and ryegrass in Georgia.

Brown patch can cause a foliar blight, which results in necrotic leaves and circular brown patches up to 4-5 ft. in diameter. High soil and leaf canopy humidity, and high temperatures increase disease severity. Higher than recommended rates of nitrogen in the spring promotes disease. Management options include avoid nitrogen application when the disease is active, avoid infrequent irrigation and allow the foliage to dry, mow when grass is dry, ensure proper soil pH, thatch reduction, and improve soil drainage.

Brown patch symptoms on a tall fescue research plot at UGA Griffin Campus (Photo Alfredo Martinez)
Brown patch symptoms on bentgrass in experimental bentgrass golf green at the UGA griffin campus (Photo Alfredo Martinez)
Brown patch lesions on tall fescue (Photo Alfredo Martinez)

Pythium blight has the potential to quickly cause significant damage to turfgrass. The disease starts as small spots, which initially appear dark and water-soaked. Affected turfgrass dies rapidly, collapses, and appears oily and matted. White, cottony mycelia may be evident early in the morning. The disease is driven by hot-wet weather, which correlates

with an increased stress on the turf. Similar environmental and cultural factors that encourage brown patch also promote Pythium.  Therefore, cultural practices for control of brown patch will also help to minimize Pythium blight development.

Pythium blight symptoms on tall fescue (Photo Alfredo Martinez)
Pythium blight symptoms on tall fescue artificially inoculated in the greenhouse. Oospores of Pythium spp (Photos Alfredo Martinez)

A correct diagnosis is important because Pythium control requires specific fungicides. Several fungicides are available for each of the diseases. Consult the 2024 Georgia Pest Management Handbook or the 2024 Turfgrass Pest Control Recommendations for Professionals for proper fungicide selection and usage. Read the label and follow proper guidelines.

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