Brown patch on tall fescue as influenced by nitrogen and fungicide applications

Abstract Tall fescue ( Festuca arundinacea Schreb.) is a cool‐season turfgrass species commonly used in the transition zone. Brown patch ( Rhizoctonia solani Kuhn) can have a significant impact on quality of tall fescue between late spring and late summer and is impacted by management strategies including fertilization and fungicide use. The objective of this study was to evaluate the influence of four nitrogen (N) sources and two application rates (0, 74 kg ha −1 [low], or 220 kg ha −1 [high] annually) along with fungicide application (azoxystrobin applied or not applied) on tall fescue brown patch infection. Highest quality occurred when tall fescue received the highest level of N and fungicide treatment. If high levels of N were applied and no fungicide was used, quality was reduced significantly when brown patch was observed in tall fescue. For example, on July 21, 2023, when most intense brown patch occurred, tall fescue had variable brown patch levels: low N levels 2%–23% and high N levels 48%–66%. Across three rating dates in summer 2023, tall fescue receiving the low N level exhibited statistically similar brown patch among all N sources. Conversely, brown patch treated with high levels of N had lower brown patch in urea compared to humic‐coated urea and slow‐release N on at least one of the three dates. Applying N at a level of 220 kg ha −1 annually or higher can result in significant brown patch in some summers; lower N levels will reduce brown patch. Desiring high tall fescue quality requires the high N level and inclusion of preventive fungicide applications.