Dollar spot: a common fungal turf disease and how to manage it in Ohio lawns

Outline skeleton

• Opening hook: a quick read on why dollar spot matters to turf managers in Ohio.

• What is dollar spot? Quick intro to the fungus Sclerotinia homoeocarpa and the dime-sized symptoms.

• Symptoms and identification: how to spot it in the field, and how it differs from other turf diseases.

• Why it shows up: conditions that invite the disease—heat, humidity, leaf wetness, and fertility stress.

• Management approach: a practical mix of cultural controls (irrigation, mowing, fertilization, thatch management) and judicious fungicide use.

• Monitoring and early detection: simple cues and a seasonal checklist.

• Real-world takeaways: why recognizing symptoms early saves time, money, and green space.

• Quick recap and encouragement to stay vigilant.

Dollar Spot: A dime-sized turf nemesis in Ohio turf systems

Let me explain why this one shows up on the radar for anyone managing turf, from athletic fields to fairways, or even those lush home lawns. Dollar spot is a common turf disease caused by a fungus named Sclerotinia homoeocarpa. The symptoms look almost casual at first—tiny circular patches that resemble little silver dollars scattered across the grass. Over time, those patches can widen, blend, and leave the turf with a patchy, unhealthy appearance. The name isn’t fancy; it’s a straight-to-the-point description of what you see on the turf: spots about the size of a silver dollar, tan-colored, and often surrounded by a subtle light green or yellow halo.

Symptoms and identification: what to look for in the field

Here’s the practical way to recognize dollar spot without second-guessing yourself:

• Patch shape and color: Circular to crescent-shaped patches, typically tan or light brown, with a slightly darker green edge when the lawn is healthy. From a distance they look like coins lying on the grass.

• Leaf texture: The turf inside the patches can feel a bit crusty or dry, and you may see the blades bending or folding, especially when the grass is under stress.

• Time of year and weather clues: Dollar spot tends to pop up in warm, humid conditions and often after periods of leaf wetness—think dewy mornings or irrigation that leaves the blade damp for longer than ideal.

• Grasses affected: It hits many cool-season and warm-season grasses alike, so the risk isn’t limited to one grass family. That broad susceptibility makes monitoring important across different turf programs.

• Distinguishing from similar diseases: Brown patch, leaf spot, and other fungi can create turf trouble, but dollar spot usually presents as smaller, rounder patches with the hallmark of the coin-size motif. If you see larger, irregular patches, you might be dealing with brown patch or another disease, and that calls for a different management focus.

Why dollar spot shows up: the conditions that invite trouble

Understanding the why helps you prevent the next outbreak rather than just react to it. Dollar spot loves a few particular ingredients:

• Heat and humidity: Warm temperatures paired with moisture in the leaf zone create a friendly environment for Sclerotinia homoeocarpa to grow and reproduce.

• Leaf wetness: Any management practice that keeps the leaf surface wet for extended periods—heavy dew, frequent overhead irrigation, or low-angle irrigation—can tilt the balance in favor of the fungus.

• Fertility stress, especially nitrogen: Ironically, while healthy turf resists a lot of stress, dollar spot tends to strike when the turf is nitrogen-deficient or otherwise stressed by drought. The turf canopy is more vulnerable under those conditions.

• Thatch and surface residues: A thick thatch layer can trap moisture near the crown and leaves, creating microclimates where the fungus thrives.

All of this translates into a simple practical rule: keep the canopy healthy and the leaf surface less hospitable to the fungus. It’s not about chasing a single magic solution; it’s about balancing culture and chemistry.

Managing dollar spot without turning turf care into rocket science

A thoughtful management plan blends cultural practices with targeted chemical tools when needed. Here’s a practical playbook you can adapt to most Ohio turf situations:

• Irrigation discipline: Water deeply but less frequently to encourage deep rooting, and aim to reduce leaf wetness duration. If you can, schedule irrigation to finish in the morning so the turf dries quickly. Avoid overnight irrigation if possible.

• Mowing practices: Maintain a mowing height appropriate for the turf species and use sharp blades. Regular mowing reduces thatch, improves air exchange, and helps the turf recover faster from stress. Don’t scalp the lawn; a stressed canopy is more vulnerable.

• Fertility management: Keep nitrogen within recommended ranges for the grass type and time of year. Avoid sudden surges after a drought or heat spell, which can create lush growth that’s still vulnerable to disease if moisture management isn’t aligned.

• Thatch and residue control: Aerate when thatch accumulates, and manage residues to reduce moisture retention near the crown. A healthier soil profile supports a sturdier canopy that resists disease pressure.

• Cultural checks throughout the season: Monitor soil moisture, adjust irrigation with the weather, and keep an eye on growth patterns. If you notice a downturn in turf vigor concurrent with dollar spot symptoms, revisiting fertility and irrigation is a good first move.

When fungicides come into play: a measured approach

Fungal products can be part of the solution, but they work best when used thoughtfully and as part of an integrated plan. Here are practical guidance points:

• Timing matters: Start preventive or early curative applications before the disease becomes obvious, especially after stretches of warm, humid weather. Early intervention can keep patches from expanding and save more of the turf.

• Product choices: Fungicides in the toen (or active ingredient) classes used against dollar spot include azoles such as propiconazole and tebuconazole, among others. Some products belong to strobilurin families or other chemical groups. Always follow label directions and resistance management guidelines, rotating among modes of action when recommended to reduce the risk of resistance buildup.

• Resistance awareness: Like many turf pathogens, Sclerotinia homoeocarpa can adapt to single-site modes of action. A rotation strategy—switching between product families over seasons—helps keep fungicides effective.

• Application hygiene: Calibrate equipment, apply under appropriate weather windows, and avoid application right before heavy rain that would wash the product away. Uniform coverage matters, so spray technique and nozzle selection matter as much as the chemistry.

A practical field guide: early detection and monitoring

Let’s keep the focus practical. Here’s a simple field checklist you can run through during routine visits:

• Look for dime-sized patches in early stages; note location, proximity to irrigation zones, and recent weather.

• Check leaf wetness duration and recent rainfall or irrigation patterns.

• Assess turf vigor in adjacent areas; a patch of weak turf nearby could indicate a spreading problem or underlying stress.

• Review fertility and irrigation records for the affected areas. If growth is slow and soil moisture is uneven, consider a targeted drought stress recovery plan.

• If patches expand, consider a modest fungicide application guided by your local extension recommendations or manufacturer labels.

• After treatment, monitor for suppression over the next 1–2 weeks and adjust cultural practices accordingly.

Real-world takeaways: why this disease deserves your attention

Dollar spot isn’t just a cosmetic nuisance. It can translate into visible turf loss, increased maintenance costs, and ongoing disease pressure if not managed. For turf management professionals and students alike, the key takeaway is simple: a proactive, balanced approach works best.

• Proactivity beats reaction: catching early symptoms and adjusting irrigation and fertility early saves more turf than waiting for the patches to spread.

• Cultural care is foundational: a healthy canopy reduces susceptibility and speeds recovery after patches appear.

• Thoughtful chemical use supports longer-term success: fungicides are helpful, but they’re most effective when used as part of a broader plan that includes cultural controls.

A few tech-friendly notes for the modern turf manager

If you’re working in field settings or study environments, you’ll find value in pairing your observations with tools that help you interpret the environment:

• Moisture sensors and smart irrigation controllers can help you maintain ideal leaf wetness durations and prevent overwatering.

• Soil testing kits and regular fertility checks keep you informed about nitrogen status and other nutrients that influence turf resilience.

• Weather stations or local extension alerts can help you anticipate conditions that favor dollar spot, so you’re not chasing patches after the fact.

• When you do apply fungicides, keep a log of product names, dates, rates, and intervals. Documenting helps you plan rotations and track effectiveness over time.

Closing thoughts: staying ahead of dollar spot

Dollar spot is a familiar foe, but it’s not unbeatable. With a clear eye on the field, a steady hand on irrigation and fertility, and a disciplined approach to monitoring and, when necessary, targeted fungicide use, you can keep patches small and recovery swift. The name itself is a reminder: look for dime-sized clues, respond with balanced care, and keep the turf healthy enough to withstand stress.

If you ever walk a turf, you’ll notice that the health of the blade isn’t just about what you apply or where you spray. It’s about how you look after the whole ecosystem—the soil, the moisture balance, the mowing routine, and the plant’s resilience. Dollar spot is a test of that balance, a small signal that turf management is both science and art—practice, patience, and a touch of field-smart intuition.

Bottom line: keep an eye out for those tiny, tan patches that resemble coins on the turf. Recognize the conditions that invite trouble, apply a disciplined cultural program, and bring in fungicides judiciously when the situation calls for it. Stay curious, stay methodical, and your turf will respond with steady, green grace.