Identifying & Preventing Dollar Spot

One of the most common turf diseases is known as “dollar spot,” a fungal infection that creates small-to-medium patches of dead grass and weakens your lawn over time. Though the damage starts as small circles of discolored grass, without proper care, this disease can spread rapidly.

Keep reading to learn how to identify the telltale signs of dollar spot in your lawn and what you can do to prevent it!

Identifying Dollar Spot

Dollar spot is a fungal disease that gets its name from the small, circular patches of brown or straw-colored grass it creates. These spots typically range from the size of a silver dollar to a few inches in diameter, but they can expand and merge over time, creating large, irregular areas of damaged turf. One of the most recognizable signs of dollar spot is the presence of tan lesions with reddish-brown borders on individual grass blades. These lesions weaken the grass, causing it to turn yellow or brown before eventually dying off.

In the early morning, you may notice a fine, cobweb-like fungal growth (mycelium) on the affected areas when dew is present. This mycelium disappears as the grass dries, making early morning inspections the best time to spot the disease. Luckily, dollar spot does not affect the roots, meaning the grass may recover if growing conditions improve.

Key Characteristics:

Small, circular patches about the size of a silver dollar
Dry, brittle grass with a straw-colored look
Fine, web-like fungal growth visible in the early morning
Distinct hourglass-shaped lesions on taller grass blades
Individual spots that can merge into larger affected areas

What Causes Dollar Spot?

Dollar spot is caused by the fungal pathogens in the Clarireedia genus, though it was formerly believed to be caused by Sclerotinia homoeocarpa. The most commonly attributed species is Clarireedia jacksonii, which lives both in the soil and on grass surfaces. This fungus is always present in the environment but only becomes active when certain conditions favor its growth.

Excessive Moisture & High Humidity: Prolonged periods of dew, high humidity, and overwatering create the damp conditions necessary for fungal growth.
Warm Temperatures: Dollar spot thrives when temperatures range between 60°F and 75°F, particularly when nights are cool, and days are warm.
Nitrogen Deficiency: Lawns with low nitrogen levels grow more slowly and become more vulnerable to disease.
Short Mowing Heights: Cutting grass too short weakens the turf, making it easier for the fungus to take hold.
Thatch Buildup & Poor Air Circulation: Excess thatch creates a humid microclimate where fungal spores can thrive, while compacted soil limits airflow, keeping moisture trapped near the surface.

Affected Grass Types

Dollar spot can infect a variety of warm-season and cool-season grasses, making it a widespread issue across different regions. However, some grass types are more susceptible than others. Cool-season grasses are particularly vulnerable, especially in regions with mild, humid conditions where moisture lingers on the grass for extended periods. In warm-season grasses, the disease is still a concern but tends to be less severe, often appearing during transitional seasons when temperatures fluctuate.

Lawns in coastal or humid regions experience more persistent outbreaks due to consistent dew and high humidity, whereas drier climates may see sporadic infections, primarily when improper irrigation or excessive thatch creates favorable conditions for fungal growth.

Affected Cool-Season Grasses:

Kentucky Bluegrass
Perennial Ryegrass
Bentgrass (especially in golf course greens)

Affected Warm-Season Grasses:

Bermudagrass
Zoysiagrass
St. Augustinegrass (less common but still possible)

How Does Dollar Spot Spread?

The spread of dollar spot occurs through fungal spores and mycelium, which can travel via wind, water, lawn equipment, and even foot traffic. General neglect and lack of maintenance is always going to lead to the spread of dollar spot. Though it is preventable, ignoring the signs of this disease and neglecting to take the proper precautions can cause the damage to spread. Once the disease takes hold, it can continue spreading rapidly if environmental conditions remain favorable. The key to controlling dollar spot is breaking the cycle before it worsens.

Infected Grass Clippings: Mowing an infected lawn can disperse the fungal spores through the clippings and organic matter (thatch).
Wind & Water: Spores can be carried to new areas by wind or splashed around by rainfall and irrigation.
Lawn Equipment: Contaminated mower blades and gardening tools can transfer fungal spores from infected to healthy areas.
Foot Traffic & Pets: People and animals walking across an infected lawn can unknowingly spread the spores.
Dew & Moisture Retention: Fungal spores become more active in wet conditions, allowing the disease to spread overnight when dew is present.

How To Prevent Dollar Spot

Preventing dollar spot requires a combination of proper lawn care practices, environmental management, and, in severe cases, targeted treatments. A well-maintained lawn is naturally more resistant to fungal diseases, so prevention starts with good lawn health and proper maintenance routines. Keep the following steps in mind to prevent fungal lawn infections on your turf.

1) Maintain Proper Lawn Nutrition: Applying the right amount of nitrogen fertilizer strengthens your grass and helps it grow vigorously, making it more resistant to disease. However, avoid excessive fertilization, as too much nitrogen can lead to other problems like thatch buildup.

2) Mow at the Correct Height: Keep your lawn at an appropriate mowing height based on your grass type. Avoid mowing too short, as this stresses the grass and makes it more vulnerable to infections. Mow when the grass is dry to prevent spreading fungal spores.

3) Reduce Excess Moisture: Since dollar spot thrives in wet conditions, adjusting your watering schedule is crucial. Water deeply but infrequently, preferably in the early morning so the grass can dry out during the day. Avoid evening watering, which prolongs moisture exposure.

4) Improve Air Circulation & Reduce Thatch: Thatch buildup and compacted soil create a damp environment that favors fungal growth. Aerate your lawn annually to improve drainage and dethatch when necessary. Pruning nearby trees and shrubs can also enhance air circulation, helping grass dry faster.

5) Overseed With Disease-Resistant Grass: Some newer varieties of Kentucky bluegrass, perennial ryegrass, and fescues have been bred to be more resistant to dollar spot. If your lawn is frequently affected, consider overseeding with a disease-resistant variety.

For help with any of these preventive treatments, or for general lawn maintenance and healthier grass in Lincoln, NE, call Summit lawns today!