Brown Ring Patch (Waitea Patch) Fungicides

Brown ring patch, also called Waitea patch, is caused by Waitea circinata var. circinata. It is most troublesome on closely mown annual bluegrass putting greens, although creeping bentgrass and other cool-season turf may also be affected.

What Brown Ring Patch Looks Like

Look for yellow, tan, or bronze rings and irregular patches ranging from a few inches to about three feet across. The center may remain green, which creates the ring pattern. Infected leaves, stems, and crowns can thin, but symptoms may resemble summer patch, necrotic ring spot, yellow patch, or localized nutrient stress. A laboratory diagnosis is valuable when the pattern is unclear.

Why It Develops

Penn State reports outbreaks most often on annual bluegrass greens during humid, overcast weather in late spring and early summer. Disease has occurred across a wide temperature range, approximately 60–95°F, so humidity, leaf wetness, and a susceptible annual bluegrass population can be more useful clues than temperature alone. Night irrigation can extend leaf wetness and increase pressure. Research also suggests that very low nitrogen fertility may worsen symptoms.

Reduce Disease Pressure

• Water early enough for the canopy to dry before nightfall and correct irrigation overlap or drainage problems.
• Use light, balanced nitrogen spoon-feeding where appropriate instead of allowing annual bluegrass to become severely nitrogen deficient.
• Improve airflow and reduce prolonged humidity at the turf surface.
• Where practical, reduce the annual bluegrass population and encourage creeping bentgrass.
• Do not assume plant growth regulators cause the disease. Penn State notes that trinexapac-ethyl alone slightly increased symptoms in one report, while programs combining it with nitrogen before disease activity produced less disease and better turf quality.

Research-Based Fungicide Strategy

University guidance still describes brown ring patch research as limited, so preventive or early applications are generally more dependable than rescue treatments after rings are well developed. Penn State lists labeled options from FRAC Groups 3, 11, 12, and 19, plus several combination products containing Groups 3, 7, 11, 12, 14, 19, 29, M5, or P1. Products available below include examples such as Densicor, Maxtima, Tourney and Tourney EZ, Medallion, Affirm, Heritage and Fame formulations, Ascernity, Briskway, Posterity XT, Honor, Lexicon, Navicon, Traction, and Pillar G.

Do not treat every product as interchangeable. Some labels state control, while others state suppression or “aids in control.” Match the product to the turf species, site, rate, and watering directions. Rotate effective FRAC groups and avoid repeated reliance on a single mode of action.

How research is presented: A university trial may show useful activity even when a current product label does not name this disease. When that occurs, the result is identified as university research rather than a label claim. Verify that the turf or application site and use pattern are permitted, then follow the product label and applicable state requirements.

University source: Penn State Extension: Brown Ring Patch.