Turfgrass Epistemology

In this episode, I interview Dr. Scott McElroy (Auburn University) about weed control in turfgrass, including best practices for herbicide timing, resistance management, and how herbicides interact with insecticides. We also discuss common mistakes, application strategies, and where to find reliable, evidence-based recommendations.

If you manage turf, this conversation will help you improve your weed identification, herbicide programs, and integrated pest management (IPM) decisions.

#turfgrass #weedcontrol #herbicides #IPM #golfcoursemanagement #turfgrassscience #agronomy 

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In this video, I break down a Floratine Masterclass where Tim Cartwright discusses a common claim about calcium availability in soils. I examine the argument, the science behind calcium in turfgrass soils, and whether the explanation actually aligns with what we know from soil chemistry and turfgrass research.

If you manage turfgrass or are interested in soil testing, calcium availability, base saturation, and turfgrass fertility myths, this discussion will help you think critically about the claims often made in the industry.

#turfgrass #soilscience #calcium #soiltesting #turfmanagement #golfcoursemanagement #turfgrassepistemology 

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In this video, I break down the research article “Soil Amendments and Fertilizer Source Effects on Creeping Bentgrass Establishment, Soil Microbial Activity, Thatch, and Disease.” We examine whether organic fertilizers, poultry meal, and humate soil amendments really improve bentgrass establishment, microbial activity, disease suppression, and thatch management on sand-based greens.

The results show that readily available nitrogen from synthetic fertilizers produced faster establishment and generally better turf quality, while organic programs increased microbial activity but did not improve establishment or consistently suppress disease.

If you manage golf greens, creeping bentgrass, or sand-based rootzones, this study prov...

In this video, I review the classic turfgrass study “Dollar Spot Severity, Tissue Nitrogen, and Soil Microbial Activity in Bentgrass as Influenced by Nitrogen Source.” We take a close look at whether organic fertilizers really suppress dollar spot and whether soil microbial activity plays the role many people claim.

The results may surprise you. The study found that disease suppression was more closely related to nitrogen availability and turf growth than to microbial activity or organic fertilizer sources. 

If you manage bentgrass fairways or want evidence-based guidance on dollar spot management, nitrogen fertilization, and organic vs sy...

In this video, I review the research article “Strategies for Increasing Ferrous Sulfate Efficacy Against Dollar Spot of Creeping Bentgrass.” We examine how ferrous sulfate (FeSO₄) can suppress dollar spot, how application techniques affect performance, and whether combining it with chlorothalonil improves disease control.

The study found that nozzle selection and application strategy influence performance, and that ferrous sulfate can reduce the amount of chlorothalonil needed and extend its effectiveness against dollar spot. 

If you manage creeping bentgrass greens or fairways, this research provides valuable insights into dollar spot management, iron applications, and fungicide optimization.

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In this episode of Turfgrass Epistemology, I critically examine the article “Exploratory Study on the Foliar Incorporation and Stability of Isotopically Labeled Amino Acids Applied to Turfgrass” (Agronomy, 2020) and use it as a case study in how “science” can be used to persuade without truly informing.

On the surface, this paper uses isotopic labeling to show that foliar-applied glutamate can be absorbed and incorporated into creeping bentgrass metabolism. But in this video, I explain why the study’s publication in a predatory journal, its direct funding and involvement by one of the product’s commercial stakeholders, and its failure...

In this episode of Turfgrass Epistemology, I break down the peer-reviewed Crop Science article “Mowing Strategies and Dew Removal to Minimize Dollar Spot on Creeping Bentgrass” by Ellram, Horgan, and Hulke (2007).

This study evaluates how mowing time, dew removal frequency, blade sharpness, and leaf wetness duration (LWD) influence dollar spot severity on creeping bentgrass fairways. I explain why mowing at 4:00 AM consistently reduced dollar spot compared to 10:00 AM, why daily dew removal outperformed alternate-day removal, and why dull mower blades did not increase disease despite common belief. The controlled-environment data also show lesion size increased dramatically as leaf...

In this episode of Turfgrass Epistemology, I discuss the Purdue Extension publication “Common Diseases on Cool-Season Lawns” (BP-218-W), a practical guide to identifying and managing diseases on Kentucky bluegrass and tall fescue.

This publication outlines major lawn diseases including dollar spot, brown patch, Pythium blight, red thread, rust, summer patch, gray leaf spot, and leaf spot/melting out, while also emphasizing the critical distinction between biotic diseases and abiotic disorders such as compaction, drought, and nutrient stress. I explain why accurate diagnosis requires understanding host species, environmental conditions, and disease spread patterns—not just visual symptoms.

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In this episode of Turfgrass Epistemology, I discuss the peer-reviewed article “Dollar Spot Resistance among Blends of Creeping Bentgrass Cultivars” by Abernathy et al. (2001), published in Crop Science.

This study evaluates whether blending creeping bentgrass cultivars can reduce dollar spot severity compared to monostands on golf course putting greens. I explain how highly susceptible cultivars like Crenshaw increased disease pressure in blends, how resistant cultivars like L-93 suppressed dollar spot, and why overall disease levels in blends often reflected a compromise between the resistance levels of the individual components.

The key takeaway: blending resistant and susc...

In this episode of Turfgrass Epistemology, I break down the classic Crop Science paper “Assessing Irrigation Management for Its Effects on Disease and Weed Levels in Perennial Ryegrass” by Jiang, Fry, and Tisserat (1998).

This study directly examines how irrigation scheduling (daily vs. ET-based irrigation) influences brown patch, dollar spot, weed pressure, pesticide use, and turf quality on perennial ryegrass fairways. I explain how ET-based irrigation reduced water use by nearly 200%, how daily irrigation suppressed brown patch but increased dollar spot, and why irrigation strategy did not significantly influence crabgrass or dandelion populations.

If you manage golf...

In this episode of Turfgrass Epistemology – Comments & Emails Part 2, I continue responding to viewer questions and email discussions about turfgrass management, soil testing, fertilizer programs, dollar spot control, and common lawn care myths.

This follow-up video addresses new comments from golf course superintendents, lawn care operators, and homeowners who are trying to separate evidence-based turfgrass science from marketing claims and social media advice. I clarify misunderstandings about nutrient ratios, iron applications, nitrogen programs, and disease suppression while explaining how to interpret research correctly.

If you’re interested in soil fertility, turfgrass disease management, golf course agro...

In this episode of Turfgrass Epistemology, I respond to viewer comments and emails covering some of the most common questions and misconceptions I see about turfgrass science, soil fertility, nutrient management, and disease control.

I address recurring themes from golf course superintendents, lawn care professionals, and homeowners, explain where confusion often arises, and clarify how peer-reviewed research should be interpreted instead of relying on anecdotes, marketing claims, or social media shortcuts.

This video focuses on critical thinking in turfgrass management, explaining how to evaluate advice, understand soil and tissue test results, and avoid common reasoning...

In this episode of Turfgrass Epistemology, I discuss the peer-reviewed article “Dollar Spot and Gray Leaf Spot Severity as Influenced by Irrigation, Chlorothalonil, Paclobutrazol, and a Wetting Agent” by McDonald, Dernoeden, and Bigelow (2006), published in Crop Science.

This landmark study examines how irrigation regime, soil moisture, and common management inputs influence dollar spot and gray leaf spot development on creeping bentgrass and perennial ryegrass fairways. I explain why dollar spot was consistently more severe under dry, infrequently irrigated conditions, how soil moisture strongly influenced disease severity late in the season, and what this means for cultural disease mana...

In this episode of Turfgrass Epistemology, I discuss and interpret the peer-reviewed article “Optimizing Liquid-Applied Iron Sulfate Rate and Application Interval for Dollar Spot Suppression on Golf Course Fairways” by Soldat et al. (2024), published in Crop Science.

This paper builds on earlier iron sulfate research and focuses on practical optimization—how rate, application interval, and spray volume influence dollar spot suppression on creeping bentgrass and annual bluegrass fairways. I explain the dose-dependent response observed across multiple locations, why 7-day reapplication intervals consistently outperformed 14-day intervals, and why spray water volume and tank-mixing with fertilizer had minimal impact on dis...

In this episode of Turfgrass Epistemology, I discuss and interpret the peer-reviewed article “Influence of Ferrous Sulfate and Its Elemental Components on Dollar Spot Suppression” by McCall et al. (2016), published in Crop Science. This paper is foundational to many modern discussions about using iron—specifically ferrous sulfate—as a tool for managing dollar spot on creeping bentgrass putting greens.

The study evaluates whether ferrous sulfate itself, or its individual components iron and sulfur, are responsible for observed dollar spot suppression. Using both field trials on USGA-spec creeping bentgrass greens and controlled in-vitro assays, the authors show that ferrous...

In this episode of Turfgrass Epistemology, I discuss and critically interpret the peer-reviewed article “Impact of Ferrous Sulfate Concentration on Clarireedia Isolate Growth and Dollar Spot Development” by Shelton et al. (2021), published in Crop Science. This paper is frequently cited in conversations about using iron—specifically ferrous sulfate—as a non-fungicidal tool for dollar spot suppression on golf course turf.

The study combines multi-site field trials with controlled in-vitro experiments to examine how ferrous sulfate rate influences dollar spot severity on creeping bentgrass fairways and putting greens, as well as how different Clarireedia isolates respond to increasing iron con...

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 exper...

In this episode of Turfgrass Epistemology, I critically examine and respond to two popular soil fertility videos that promote base saturation theory and a simplified soil pH–nutrient availability diagram, and I explain why both should be treated with extreme skepticism—or ignored entirely—when making turfgrass management decisions.

Much of the base saturation messaging presented in these videos relies on the idea that soils must be managed toward specific “ideal” cation percentage ratios to achieve productivity. In this video, I explain why base saturation is not a causal driver of turfgrass performance, why the concept persists despite de...

In this episode of Turfgrass Epistemology, I walk through a recent peer-reviewed study that examines how potassium fertilization influences dollar spot severity on annual bluegrass (Poa annua) and creeping bentgrass (Agrostis stolonifera) putting greens.

The article, Potassium fertilization effects on dollar spot of annual bluegrass and creeping bentgrass, presents multi-year field data showing that increasing potassium rates consistently increased dollar spot severity under the conditions tested. This directly challenges the common assumption that potassium fertilization automatically improves stress tolerance or reduces disease pressure in turfgrass systems.

In the video, I explain the experimental design, including...

In this episode of Turfgrass Epistemology, I review and respond to comments, emails, and TikTok messages I’ve received throughout 2025 related to turfgrass science, soil fertility, nutrient management, and common turf industry claims.

From thoughtful questions to recurring misconceptions, this video highlights what turf managers, lawn care professionals, golfers, and homeowners are asking—and where confusion often arises when science meets social media. I address trends I’ve seen across platforms, clarify misunderstandings, and explain why certain claims persist despite decades of research.

Topics discussed include:
Common turfgrass myths repeated in social media comments
Mi...

In this episode of Turfgrass Epistemology, I sit down with Dr. John Inguagiato to discuss his peer-reviewed research on phosphite use for suppressing cyanobacteria (blue-green algae) on putting greens. Together, we break down the science behind phosphite chemistry, application rates, turf safety, and what the data actually say—beyond marketing claims.

Dr. Inguagiato’s 2017 Crop Science paper, “Effect of Phosphite Rate and Source on Cyanobacteria Colonization of Putting Green Turf,” is one of the most frequently cited studies on this topic. In this conversation, we explore how phosphite differs from phosphate, why cyanobacteria respond differently to these compound...

In this video I take a close, critical look at "Data-Drive Lawn Care" (https://www.youtube.com/watch?v=pjRXNcIi3Hk) and share my honest thoughts on what works — and what doesn’t. I break down the arguments, highlight where I think the logic falls short, and offer my own perspective on the topic.

🔎 What I cover:

Key claims made by the original creator

Moments where I agree — and moments where I respectfully disagree
Glaring omissions and what I believe should have been addressed
My own take: what’s convincing, what needs more...

In this video, I review and break down one of the most referenced articles in cool-season turfgrass pathology: “Severity of Gray Leaf Spot in Perennial Ryegrass as Influenced by Mowing Height and Nitrogen Level” by Williams, Burrus, and Vincelli (2001).

This study investigated how two major management practices—mowing height and nitrogen rate—affect the intensity of gray leaf spot (Pyricularia grisea) epidemics in perennial ryegrass managed under golf-course conditions.

I walk through the methods, results, and implications of the research, and I discuss how the findings align—or don’t align—with common industry assumptions twenty years l...

In this video, I provide an in-depth, evidence-based critique of the nitrogen-efficiency product RDX-N and the claims made in the promotional video circulating online. If you’ve ever wondered whether biostimulants, nitrogen enhancers, or “metabolic activators” actually work in real-world turfgrass or crop management, this breakdown is for you. I review the product’s marketing claims, examine the data presented in the official RDX-N brochure, and explain what the science really says about nitrogen uptake, nitrogen metabolism, and plant physiology.

But this video is more than a review of one product—it's a lesson in how to evaluate a...

In this episode of Turfgrass Epistemology, I sit down with Dr. Lee Miller of Purdue University, one of the leading experts in turfgrass pathology, to break down everything you need to know about turfgrass disease resistance, fungicide rotations, and accurate turf disease identification. Whether you manage golf course greens, sports fields, or home lawns, this conversation gives you the practical, science-based guidance needed to protect your turf from common and emerging diseases.

We explore what disease resistance in turfgrass truly means, why resistance develops, and how environmental conditions and management practices influence disease pressure. Dr. Miller explains...

In this video, I analyze the 2025 Zhang et al. study on how fungicide scheduling and bentgrass cultivar resistance interact to influence dollar spot control. This research provides some of the strongest evidence to date that curative, damage-threshold-based fungicide programs can dramatically reduce inputs—up to 78 percent in certain cases—when paired with disease-resistant bentgrass cultivars. I explain how the researchers designed the field trials, what the low damage threshold means in practice, how 24-hour and next-application-day schedules performed differently, and why resistant cultivars such as Declaration produced such large savings without sacrificing control. I also discuss how inoculation affected dise...

In this video, I break down one of the most influential papers ever written on turfgrass pathology: Walsh, Ikeda, and Boland’s 1999 review on the biology and management of dollar spot. This paper remains a foundational resource for understanding how the pathogen operates, why the disease is so persistent on cool-season turf, and which management strategies are supported by evidence rather than tradition. I walk through the key sections of the paper, including the pathogen’s life cycle, the environmental conditions that drive epidemics, the role of cultural practices, and the strengths and weaknesses of common fungicide approaches. I also...

In this episode of Turfgrass Epistemology, I review a popular lawn-care website article and an accompanying YouTube video that teach homeowners how to interpret a soil test that is, in reality, scientifically invalid for making nutrient decisions. These resources look polished and authoritative, but the advice they provide is fundamentally flawed — and following it can lead to unnecessary product applications, wasted money, and incorrect assumptions about soil health.

I’ll walk through both the website and the video step-by-step and explain:

Why the soil test they promote is not valid for nutrient recommendations
How cert...

Not all scientific journals are created equal. Some exist to advance knowledge — others exist to collect publishing fees. In this episode of Turfgrass Epistemology, we explore how to tell the difference.

I’ll walk through the refereed process and explain how it differs from standard peer review, why that distinction matters, and how the structure of editorial oversight determines the credibility of the science that reaches the public. We’ll also take a close look at predatory journals — publications that mimic legitimate science while bypassing or corrupting the review process in exchange for author fees.

But the...

In this episode of Turfgrass Epistemology, we take a close look at one of the most frequently cited studies in turfgrass pathology — Golembiewski and Danneberger’s 1998 Agronomy Journal paper exploring how trinexapac-ethyl (TE) and nitrogen fertility influence the severity of dollar spot (Sclerotinia homoeocarpa) in creeping bentgrass.

The researchers found that TE, a popular plant growth regulator, didn’t increase disease as many feared — in fact, it reduced dollar spot when combined with adequate nitrogen. This discovery challenged the prevailing assumptions of the time and suggested that growth regulation and fertility could work together to reduce fungicide reliance...

In this episode, I sit down to talk about a topic that’s been at the heart of American higher education for more than a century — university extension. We’ll explore how extension began, why it was once the lifeblood of land-grant universities, and how the system that connected science to society is now quietly disappearing.

Extension was created so universities could serve the public — not just by publishing papers, but by helping real people solve real problems. For decades, that mission worked. Faculty were rewarded for outreach, and industries like turfgrass, horticulture, and agriculture thrived because science...

Can something as simple as mowing time really stop a turfgrass disease? In this episode of Turfgrass Epistemology, we look back at a landmark 1996 study by Williams, Powell, Vincelli, and Dougherty from the University of Kentucky — a paper that changed how superintendents think about dew, nitrogen, and dollar spot control.

Dollar spot (Sclerotinia homoeocarpa) thrives on leaf moisture. Williams et al. tested what happens when you simply remove that moisture early in the morning. Their data were stunning — mowing or “poling” to knock dew off reduced dollar spot by as much as 81% on fairways and 53% on greens. That’s b...

In this video, I explore the history and current state of university turfgrass programs—from their rise during the post-war boom in golf, parks, and sports fields to their decline in recent decades. I explain how turfgrass faculty positions are created and filled, what factors lead to the loss of those positions, and why many programs are now disappearing altogether. I connect the dots between enrollment trends, industry funding, and the shifting priorities of universities that have left turfgrass science struggling to survive. Most importantly, I discuss what the turfgrass community—educators, managers, and industry leaders—can do to revers...

In this video, I examine the 2021 study by Beckley and Roberts published in the International Turfgrass Society Research Journal titled “Utilizing Organic Amendments for General Suppression of Dollar Spot on Creeping Bentgrass.” The discussion centers on one key question: Does biochar actually reduce dollar spot? I break down the experimental design—how researchers compared biochar, compost, vermicompost, and traditional fertilizers under equal nitrogen rates—and explains what the data really show. Were the reductions in dollar spot due to microbial changes, or simply better nitrogen nutrition? You’ll see how biochar performed across two years, why the results were inconsiste...

In this video, I explore the recent review article “Review of the Biology and Management of Large Patch of Warm-Season Turfgrasses” (Kreinberg et al., Crop Science, 2025). I walk you through what the authors tell us about Rhizoctonia solani AG 2-2 LP — the fungal pathogen behind large patch disease in warm-season turfgrasses — how environmental conditions favor its development, and how it can persist in thatch through seasonal dormancy. Along the way, I highlight the state of current cultural, chemical, and biological control strategies, and I point out the gaps and future directions the turfgrass pathology community still needs to address. If you’r...

In this video, I take you through the state of the science on dollar spot disease in turfgrass, framed by the recent review “New Approaches to an Old Problem: Dollar Spot of Turfgrass.” We explore how this ubiquitous fungal disease (caused by Clarireedia spp.) continues to challenge turf managers, why traditional fungicide programs are increasingly under pressure, and what new genomic tools and breeding strategies may offer as solutions. I’ll break down the authors’ discussion of pathogen genomics, host–pathogen interactions, and quantitative trait loci (QTL) for resistance, while also reflecting on where future research might be headed. Whether yo...

In this video, I dive into the article “Survey of Water Use and Management Practices on US Golf Courses from 2005 to 2024” published in HortTechnology (Shaddox et al., 2025). The study tracks nearly twenty years of changes in how golf courses across the United States use and manage water. I discuss how irrigation volumes and irrigated areas have shifted over time, highlight important regional differences, and explain why some water sources—like recycled water—are declining while others remain steady. I also cover the adoption of new management strategies such as moisture sensors, irrigation audits, and objective scheduling, along with the continui...

In this video, I discuss the YouTube episode “Struggling Turf? Calcium Could Be the Missing …” and examine it through the lens of the strawman fallacy. We’ll look at how someone can present information that is technically true, yet still mislead by reframing the issue or knocking down an argument no one actually made.

This breakdown shows how a conman can be both truthful and deceptive at the same time—a powerful reminder of why critical thinking matters in turfgrass science, lawn care, and beyond.

If you’ve ever learned something useful from this channel, please consi...

In this video, I review the scientific article “Irrigation Frequency Affects Zoysiagrass Rooting and Plant Water Status.” We’ll look at how different irrigation schedules influenced root development and water relations in zoysiagrass, and what these findings mean for turfgrass management. If you’ve ever wondered how often you should water to encourage deeper roots and better turf performance, this study offers valuable evidence-based insights.

Article: https://journals.ashs.org/view/journals/hortsci/31/2/article-p234.xml

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In this episode, I break down the claims made in “Check out These Roots, John Perry! | [LIVE PODCAST] Ep.8 of the Average Joe Lawn Care Show,” where the hosts argue that liquid aeration is an effective solution for lawn health. I dive into the science and present evidence that challenges their assertions. With years of turfgrass science experience, I explain why liquid aeration doesn’t deliver the promised results and why relying on this product could lead to misguided lawn care practices. Don’t fall for the hype – join me as I debunk the myths and set the record straight w...