With the continued cool wet weather, Rhizoctonia Large Patch (RLP or zoysia patch) is in high gear. This follows a warm winter that also encouraged RLP, which is the only major disease of zoysiagrass in Indiana. Like snow mold, a rust to orange colored band on the outside of the patch indicates activity. Though best control is usually with fungicides applied in fall, we have experienced significant RLP suppression with Heritage, Compass, Insignia, or Prostar applied at about 50% green-up of the zoysia. Even mid-summer applications have helped to knock back the RLP in our research. Is it worth it to spray now? Our recommendation is to spray the areas with a substantial threat of bermudagrass filling in the thinned zoysiagrass. In areas with solid zoysia and no bermudagrass (centers of fairways, newly established areas), an application may not be warranted. Our current research is investigating potential varietal differences in susceptibility to RLP. Unfortunately, this will not help current areas of infected zoysiagrass, but it may help dictate future selection of zoysia cultivars for your course. More information about Rhizoctonia Large Patch is available at: http://www.extension.purdue.edu/extmedia/BP/BP-117-W.pdf
