Evaluation of Spring and Fall Fungicide Applications for Large Patch Management in Zoysiagrass

The efficacy of spring and fall applications of azoxystrobin, flutolanil, and triticonazole for the control of large patch disease of zoysiagrass (Zoysia spp.) caused by Rhizoctonia solani Kühn AG 2-2 LP were evaluated under field conditions. The study was conducted on fairway stands of ‘Meyer’ zoysiagrass from 2008 to 2010 at the Rocky Ford Turfgrass Research Center, Kansas State University. Experimental plots were inoculated prior to the start of the studies. All fungicide applications were made with a CO₂–powered boom sprayer with XR Tee Jet 8003VS nozzles at 206.8 kPa in water equivalent to 816 L ha⁻¹. Disease assessment was performed by measurement of patch diameters, visual assessment, and by analysis of digital images of affected plot areas. In general, two fall applications of fungicide did not reduce disease compared with one fall application. Fall applications made when thatch temperatures ranged from 17.8 to 23.2°C reduced disease relative to untreated controls. Similarly, two spring applications of fungicide, beginning at an early curative timing, did not reduce disease compared with one spring application.