Brown Ring Patch
A new disease of annual bluegrass greens that appeared in weather too warm for Yellow Patch (Rhizoctonia cerealis) was first noticed in 2004 and 2005. Yellow Patch typically occurs between 50-65° F; the new disease appeared between 60-95° F. Outbreaks occurred in both cool and hot weather, always on annual bluegrass, and a Rhizoctonia-like fungus was consistently isolated. Initially termed warm temperature yellow patch, the disease has had numerous names since then including brown ring patch, yellow ring, R. zeae, Sheath and leaf spot, and Waitea patch.
Symptoms first appear as yellow rings ranging from a few inches to a foot, which turn light brown to reddish brown as the disease progresses. The turfgrass is slow to recover. Further investigation (including molecular fingerprinting) identified the pathogen as Waitea circinata var. circinata, a "new" Rhizoctonia species, and the disease has been named Brown Ring Patch. In 2006 and 2007, disease symptoms appeared throughout New England and New York in the spring and early summer. The pathogen has been confirmed as causing disease on annual bluegrass in ten states and also on rough bluegrass (Poa trivialis). Reports of Brown Ring patch on creping bentgrass first appeared in 2008 although the pathogen does not appear to affect perennial ryegrass, fescues, or Kentucky bluegrass.
Brown Ring Patch is similar to other Rhizoctonia species, but appears to infect upper roots, crowns, and stems as well as foliage of individual plants. It also degrades thatch, gives rise to sunken rings, and acts somewhat like superficial fairy ring. Brown ring patch is limited to putting greens. Height of cut seems to play a big part in the susceptibility of plants to the disease and symptoms are far less severe on higher-cut turf. Cultural conditions associated with brown ring patch include low nitrogen fertility and thatch accumulation. The pathogen attacks the foliage as well as the thatch, so excess thatch favors disease development. Moist weather, fog and overcast conditions promote disease development, although the role of rainfall is not well understood.
- Research in 2008 demonstrated that 1 pound of nitrogen per 1,000 sq ft (nitrate, ammonium or urea) could reduce disease by 50 percent or more. Maintain greens with adequate nitrogen.
- Reduce thatch aggressively by verticutting and/or aerifying in the spring and fall when the turf is actively growing.
- Raise the mowing height prior to and during summer stress periods.
- Cultural practices that promote healthy turf will promote turf recovery.
- The use of surfactants and larger spray volumes may improve fungicide efficacy.
Management with Fungicides
Most fungicides labeled for control of Rhizoctonia are active against Brown Ring Patch, with the exception of thiophanate-methyl (Cleary's 3336TM), but their curative activity is much less than their preventive activity. Tank mixes or pre-mixtures of active ingredients may be more effective than applications of a single fungicide. Applications should be made preventively where there is a history of the disease.
For a listing of fungicides currently labeled to manage this disease, refer to the Disease Management chapter of UMass Extension's Professional Guide for IPM in Turf for Massachusetts.
Written by: M. Bess Dicklow