S4 E3 Does Nitrogen Suppress Dollar Spot?

In this episode of Turfgrass Epistemology, I break down and discuss the peer-reviewed article “Dollar Spot Suppression on Creeping Bentgrass in Response to Repeated Foliar Nitrogen Applications” by Townsend et al. (2021), published in Plant Disease. This paper directly addresses one of the most common and controversial questions in turfgrass management: can nitrogen fertilization meaningfully suppress dollar spot without relying solely on fungicides? The study evaluated repeated foliar nitrogen applications on creeping bentgrass putting greens across multiple years and locations, using a spoon-feeding approach that mirrors how many golf course superintendents manage fertility today. I walk through the experimental design, nitrogen rates, nitrogen sources, and how dollar spot severity responded over time. A major focus of the discussion is why only the highest nitrogen rate consistently reduced dollar spot severity, while lower, more typical spoon-feeding rates provided little to no disease suppression. In this video, I explain what the results actually show—and just as importantly, what they do not show. While nitrogen clearly influenced dollar spot development, the rate required to achieve meaningful suppression raises practical, agronomic, and environmental concerns. I also discuss how nitrogen source had minimal and inconsistent effects, why foliar nitrogen concentration may be more informative than application rate alone, and how these findings fit into integrated pest management strategies rather than stand-alone fertility “solutions.” This episode is especially relevant for golf course superintendents, turfgrass researchers, and advanced turf managers who hear that “more nitrogen reduces dollar spot” without adequate context. The data demonstrate that the relationship between nitrogen and disease is real but non-linear, highly rate-dependent, and constrained by tradeoffs involving growth, thatch accumulation, environmental risk, and secondary disease pressure. As always, the goal of this discussion is evidence-based interpretation, not fertilizer folklore or oversimplified recommendations. If you are making fertility decisions to manage dollar spot on creeping bentgrass putting greens, this video will help you better understand how nitrogen fits into the bigger disease management picture. Subscribe for more long-form turfgrass science discussions, peer-reviewed paper breakdowns, and clear explanations focused on how we know what we know in turfgrass management. Don’t forget to like, share, and subscribe to stay updated on more science-driven insights! Become a member of Turfgrass Epistemology and support turfgrass research: www.youtube.com/@TurfgrassEpistemology/join Voicemail: 859-444-4234 Apple Podcast https://podcasts.apple.com/us/podcast/turfgrass-epistemology/id1717271379 Spotify Podcast https://open.spotify.com/show/1cTpdrChToeEFAOX9wkXFI iHeart Radio Podcast https://www.iheart.com/podcast/1323-turfgrass-epistemology-129043524/ Podbean https://turfgrassepistemology.podbean.com/ Online consulting Calendly.com/TravisShaddox Twitter Twitter.com/TravisShaddox Email [email protected] Turfgrass Programs and Extension Service Information: https://www.usna.usda.gov/assets/images/as_pdf_image/LandGrantColleges.pdf