Dollar Spot Disease: Lawn Treatment and Prevention

There’s nothing quite like the pride of a lush, green lawn, so it can be truly disheartening to see it marred by unsightly brown patches. One of the most common culprits behind this is dollar spot, a turf disease that leaves silver-dollar-sized circles of dead grass in its wake. This guide is here to walk you through everything you need to know, from spotting the first signs to effective treatment and prevention, helping you restore your lawn to its former glory.

What is Dollar Spot and why should you care?

Dollar spot is a fungal disease that creates small, distinct, straw-colored spots on turfgrass, each roughly the size of an old silver dollar coin. If left unchecked, these spots can merge and form large, irregular patches of blighted turf.

It primarily affects fine-textured grasses and is a common headache for anyone managing bentgrass, bluegrass, ryegrass, fescue, and zoysia grass. While it’s a nuisance for home lawns, it’s a major concern for golf course superintendents and sports field managers. The disease can severely impact the playability and aesthetic quality of high-value turf, requiring costly and intensive management to keep it under control.

What causes Dollar Spot in grass?

The disease is caused by the fungus Clarireedia spp. (formerly known as Sclerotinia homoeocarpa). This fungus survives in the thatch layer and soil as dormant mycelium or on infected plant debris.

Dollar spot thrives under specific environmental conditions. It becomes active during periods of high humidity and fluctuating temperatures, typically when days are warm (15–30°C or 60–85°F) and nights are cool, leading to heavy morning dew. Prolonged leaf wetness is the single most important factor for infection. The fungus requires the grass blades to be wet for at least 8 to 10 hours to penetrate the plant tissue.

It spreads easily across a lawn through water splash from rain or irrigation, on mowing equipment, shoes, and even by wind carrying infected grass clippings.

How do you recognize Dollar Spot symptoms?

Spotting dollar spot early can make a huge difference in how easily you can control it. Here are the key visual cues to look for:

• Early signs: The first indication is the appearance of small, round, sunken spots of straw-colored grass, about 2-5 cm (1-2 inches) in diameter. In the early morning, when dew is present, you might see a cobweb-like, white fungal growth (mycelium) covering the affected spots.
• Distinct leaf lesions: If you look closely at the individual grass blades within the patches, you’ll see a very characteristic symptom: an “hourglass” shaped lesion. These lesions are bleached white or straw-colored in the middle with reddish-brown or purplish borders.
• Merging patches: As the disease progresses, the numerous small spots will grow and merge, creating large, ugly, and irregular areas of dead-looking grass.

What factors increase the risk of Dollar Spot?

Certain lawn conditions can make your turf much more susceptible to a dollar spot outbreak. These include:

• Poor nitrogen levels: Lawns that are under-fertilized and deficient in nitrogen are significantly more prone to the disease.
• Excessive thatch buildup: A thick layer of thatch (dead grass stems and roots) creates a perfect, moist environment for the fungus to live and thrive.
• Overwatering or prolonged leaf wetness: Watering in the late evening, frequent light sprinklings, or poor drainage keep grass blades wet for extended periods, inviting infection.
• Compacted soil: Soil compaction restricts airflow and water movement to the roots, stressing the grass and making it more vulnerable to disease.

How can you prevent Dollar Spot?

A healthy, resilient lawn is your best defense. Here are the most effective prevention strategies:

• Balanced fertilization: Maintain adequate nitrogen levels, especially during the spring and fall. A soil test can help you determine the exact needs of your lawn.
• Proper mowing: Mow at the recommended height for your grass type and do so frequently, removing no more than one-third of the leaf blade at a time. This reduces stress on the plant.
• Smart watering: Water deeply but infrequently in the early morning. This allows the grass blades to dry quickly once the sun is up, minimizing the window for fungal infection.
• Thatch control and aeration: Dethatch your lawn if the thatch layer is more than 1.25 cm (1/2 inch) thick. Aerate annually to reduce soil compaction, which improves air circulation and water drainage.

How can you treat Dollar Spot once it appears?

If dollar spot has already taken hold, a combination of cultural practices and chemical treatments may be necessary.

• Fungicide options: Fungicides containing active ingredients like propiconazole, myclobutanil, or azoxystrobin are effective. It’s crucial to rotate fungicides with different modes of action to prevent the fungus from developing resistance. Always apply according to the label’s instructions.
• Cultural practices: Continue your prevention strategies rigorously. Lightly fertilizing with nitrogen can often help the grass outgrow the damage. Improving air circulation by pruning nearby trees or shrubs can also help reduce humidity and leaf wetness.
• Combined approach: For the best results, combine chemical and non-chemical methods. Use fungicides to get the immediate infection under control while simultaneously improving your lawn care practices to build a stronger, more disease-resistant turf for the long term.

Conclusion

In the end, creating a beautiful lawn is about staying one step ahead of problems like dollar spot through consistent, smart care. For an extra layer of defense, the Planteyes app is a fantastic tool that helps detect lawn diseases from a simple photo. Plus, you can chat with an in-app expert for tailored advice, making you feel like you have a lawn care pro in your pocket. Download it today to give your lawn the best chance to thrive.

FAQs