Influence of Nitrogen Rate and Timing, Fungicide Application Method, and Simulated Rainfall after Fungicide Application on Brown Patch Severity in Tall Fescue

Abstract

Core Ideas Tall fescue lawns can be fertilized during the summer months at modest N rates without affecting brown patch severity. When an appropriate fungicide such as Heritage was used for brown patch management, the method of fungicide delivery did not affect brown patch suppression. Simulated rainfall up to 0.5 inches within 15 min of fungicide application did not compromise fungicide efficacy. In North Carolina, tall fescue (Festuca arundinacea Schreb.) is widely grown throughout the Mountain and Piedmont regions. North Carolina is in the transition zone, which is subject to hot, humid summers that predispose tall fescue to brown patch (Rhizoctonia solani Kühn). Field trials were conducted over a 2-year period (2015–2016) to evaluate the effects of nitrogen rate and timing, application method of a fungicide, and rainfall following fungicide application on brown patch severity on lawn height tall fescue. Seven rates of urea providing 0 to 6 lb N 1000 ft-2 year-1 were initiated each year in March with repeat applications monthly at 1 lb N 1000 ft-2. In a separate study, various timings of urea were conducted throughout the year for a total of 3 lb N 1000 ft-2 yr-1. In 2015, no significant differences in disease severity or turfgrass quality were observed among the seven N rates. Only the application of 6 lb N 1000 ft-2 yr-1 resulted in significantly higher brown patch compared with the non-treated control in 2016. No significant differences in disease severity or turfgrass quality were observed in the timing study in both years. Azoxystrobin was applied with a ride-on spreader/sprayer (11 gal water-carrier acre-1), a commercial applicator gun (130 gal water-carrier acre-1), and a research spray boom (88 gal water-carrier acre-1). No differences were detected among application methods. A rainfall event of 0.5 inches was simulated with overhead irrigation 30 min after application of fungicides. No differences were detected among the fungicide treatments, and all provided excellent control of brown patch.