Effects of Cultivation and Fertilization Timing On Large Patch Disease of Zoysiagrass.

Large patch, caused by Rhizoctonia solani AG 2-2 LP, is the most common and severe disease of zoysiagrass and is managed primarily by fungicides. The effects of summer cultivation (aerification, verticutting and sand topdressing) and time of nitrogen (N) fertilization on large patch development were evaluated on inoculated plots in a split-plot design with four replications. The whole plot treatment was cultivation vs no cultivation. The subplot treatment was timing of fertilization, with one summer application at 90 kg N/ha as polymer-coated urea or spring and fall applications of 45 kg N/ha each (90 kg N/ha annual total) as urea. Large patch was assessed through patch size measurements and digital image analysis. Neither cultivation nor fertilization timing had any significant effect on patch size in 2008. In 2009, cultivation and summer fertilization resulted in smaller patches compared with non-cultivation and fertilization in spring and fall. However, as measured by digital image analysis, recovery of zoysia from large patch infection was faster in non-cultivated plots, irrespective of the timing of fertilization. In 2010 there were no significant differences among any treatments. To assess differences in microclimate that may impact disease, soil temperature, thatch temperature, and soil moisture content were evaluated using soil-encapsulated thermocouple sensors and dual-probe heat-pulse sensors. There were no differences in any environmental parameters in cultivated versus non-cultivated plots.