A prolonged period of mild, wet weather has provided optimum conditions for the development of Waitea patch, and several golf courses in the region have reported the disease this spring. Also called brown ring patch, Waitea patch is caused by Waitea circinata var. circinata. This fungus is a close relative of Rhizoctonia cerealis, which causes yellow patch, and Rhizoctonia solani, which causes brown patch.
Waitea patch is typically a problem on golf course putting greens and is not an issue on lawns. Annual bluegrass, rough bluegrass, and bentgrass are most susceptible. The disease appears as yellow arcs or rings in the turf that eventually turn brown. On bentgrass, rings may initially be more orange in color. Individual rings are 2-12” in diameter and may coalesce to produced what is described as a scalloped pattern. The rings may be slightly sunken, and turf inside or just outside of the rings may be greener than the surrounding turf due to the release of nutrients as thatch is degraded. Fluffy white mycelium may be visible under humid conditions. The fungus is capable of infecting turf roots, crowns, and leaves. Although the temperature optimum for disease development is about 70-80°F, the disease is most often observed when temperatures are cooler and turf growth is slow. High humidity, low light levels, and low nitrogen fertility are also conducive to disease development.
In terms of management, scout for symptoms after spates of cool, wet weather. Provide adequate nitrogen fertilization; if fertility is low, a small boost in soil nitrogen alone can significantly reduce symptoms. Raise mowing height when possible. In areas with a history of disease, preventive fungicide applications may be advisable. As the pathogen inhabits the thatch layer, fungicides should be applied in a volume of 2 gal/1000 ft2 and lightly watered in. Curative applications are less effective than preventative ones and several treatments may be necessary. Note that benzimidazoles are ineffective against Waitea patch. For a listing of fungicides currently labeled to manage this disease, please see UMass Extension's Professional Guide for IPM in Turf for Massachusetts. Check labels and ensure that products are registered for use on turf in your state.
Submitted by: Dr. Angela Madeiras