Dollar Spot is a fungal lawn disease that can infect both warm- and cool-season grass types. This disease causes unsightly patches of yellow or tan grass to develop on low-mowed lawns. Though Dollar Spot is most often identified by the small size of the infected patches it leaves behind, those small patches often melt together to form widespread damage across your entire lawn.
Symptoms Of Dollar Spot
Identifying Dollar Spot on a lawn is not overly difficult because of the unique damage the Dollar Spot disease causes. Dollar Spot is a foliar disease, which means that the infection is limited to the leaf of the plant rather than affecting the roots. Affected grass blades begin developing straw-colored markings that are typically surrounded by a brownish border. These markings begin at the tips of the leaf blades and slowly work their way down to infect the entire blade of grass. Older lesions form into an hourglass shape on higher-mowed lawns, which is an easy identifier of Dollar Spot.
On lawns that are mowed low to the ground, we can see where this fungal lawn disease gets its name. Dollar Spot is known to form small patches of damaged turf on residential lawns. While tall grass will show damage more on individual blades of grass, Dollar Spot forms silver-dollar sized patches on lawns with short grass. These patches initially measure only a few centimeters in diameter, but these smaller patches often spread and combine into larger patches of discolored turf. Early in the morning, you may be able to notice a cobweb-like mycelium spreading across infected patches on your lawn.
What Causes Dollar Spot To Spread?
In the 1930’s, Dollar Spot was first identified, and it was believed to belong to the Sclerotinia homoeocarpa fungal species. However, debate has gone on ever since the discovery of this disease to try to determine if it is actually caused by this fungus. In recent years, it has become accepted that Dollar Spot is caused by several species of a different fungus, the most common of which is believed to be Clarireedia homoeocarpa.
These fungi love warm and humid conditions, which is why Dollar Spot is most often found between spring and fall. The ideal temperature for Dollar Spot to form is between 60-77 degrees Fahrenheit. However, this disease can still occur outside of these temperature ranges if the humidity is high enough. If you live in an area with frequent morning dew or fog, your lawn may be more susceptible to developing Dollar Spot. Make sure all areas of your lawn are draining properly to avoid hazardous puddles or standing water.
As previously mentioned, Dollar Spot spreads via mycelium that is typically found sprawling across infected patches in the early morning hours. This is not the only way that Dollar Spot can spread, however. The disease can also be transported by wind, mowers, rakes, and other lawn equipment. If you have diagnosed Dollar Spot on your lawn, it is important to take care when handling infected grass clippings and debris. Be sure to properly dispose of any infected material so that the disease does not have a chance to spread further.
Will Dollar Spot Kill Your Grass?
Luckily, Dollar Spot does not affect the roots or crown of grass, which means it will not kill your lawn. This does not mean that an infection will not damage your grass. Older lesions on grass blades eat away at the leaf until it collapses, which makes healthy regrowth more difficult. An infection can cause your grass to thin out and become weaker, which will leave your lawn susceptible to other problems. Weeds will have an easier time taking root in spots where grass has thinned, and your lawn will be more likely to experience drought damage and erosion.
Dollar Spot is known to overwinter, so do not expect the cold weather to kill off this disease. The fungus survives in fungal stroma of dead plant tissue, and it infects damaged glass blades as they emerge during the following spring. While it may be alarming to see sick grass blades so early in your lawn’s growing season, remember that this disease does not spread via spores and does not damage roots. Pay close attention to your lawn care routines, and your lawn should have no trouble recovering from Dollar Spot.
Affected Grass Types
Like many fungal lawn diseases, Dollar Spot infects all types of grass in a variety of climates. Both warm-season and cool-season grass types can become infected, but some are more susceptible than others. The most commonly affected grasses include the following:
- Creeping Bentgrass – This is a cool-season grass that is often used for golf courses and low-mowed lawns, which creates an ideal environment for Dollar Spot.
- Annual Bluegrass – As the name suggests, this is a grass that only lasts for one season. It germinates in the fall and dies off in the spring, which makes it susceptible to Dollar Spot during its short lifespan.
- Perennial Ryegrass – Another cool-season grass, this type of grass is often used for overseeding lawns in colder climates. Perennial ryegrass is also used on soccer fields and other high-traffic areas where a durable grass is needed.
- Zoysiagrass – Zoysiagrass is a warm-season grass that is common in the southern United States. This type of grass has a higher tolerance to Dollar Spot than bentgrass and ryegrass, but it is still susceptible to the disease.
Preventing & Treating Dollar Spot
The best way to prevent Dollar Spot is to maintain a healthy lawn. Be sure to mow your grass at the recommended height for your grass type and fertilize regularly. Water deeply and less frequently to encourage deep root growth. If you live in an area with high humidity, make sure that your lawn has good drainage so that water does not pool on the surface of the grass.
Low nitrogen levels are believed to be linked to Dollar Spot, so it is important to make sure you are fertilizing appropriately for each season and grass type. You also want to make sure not to over-fertilize your lawn, which could lead to dead grass. Frequent applications of low-nitrogen fertilizer is a good way to both prevent and treat this disease.
In addition to excess moisture causing fungal disease, dry or drought-stressed lawns are also susceptible to Dollar Spot. Be sure to water your lawn deeply and less frequently to maintain a healthy level of moisture for your soil that will not drown your lawn or deprive it of adequate hydration. Also, remember that watering should always take place early in the morning to avoid the development of fungi.
Low mowing heights create the ideal environment for Dollar Spot. Be sure to mow your lawn at the recommended height for your grass type to help prevent this disease. If you do notice Dollar Spot, raise your mowing height until the lesions have healed and new growth has filled in any thin or bare spots. In general, try to avoid removing more than the top 1/3 of grass length in order to maintain a resilient lawn.
Certain cultivars of grass are more tolerant to disease than others. Mixing tolerant grass types into less-tolerant lawns can help deter fungal infection. For Dollar Spot specifically, creeping bentgrass is frequently affected because it does not grow too tall, so overseeding with a more resilient grass type, such as colonial bentgrass, can stop or slow the spread of infection.
Fungicides are effective against Dollar Spot, but applying them can be tricky if you don’t know what you are doing. Chemical control must be applied at an appropriate rate during the season in which the disease is most active, otherwise you may damage your lawn. Always consult with a local lawn care expert before using any fungicides on your lawn.