Dollar spot is a turf disease primarily caused by fungus Sclerotinia homoeocarpa. This disease is most common with high maintenance turfgrasses like those found on golf courses or sports fields, however, it’s not uncommon for it to be spotted in residential lawns. It is becoming a more serious concern for lawn owners in the U.S. because of the extension of this disease in the country.
The disease can weaken the roots and the quality of the grass internally, making it harder for the grass to survive in fall.
Let’s start by taking a basic look at the appearance and description of a dollar spot. This description will make identifying the problem much easier.
What does dollar spot look like?
Dollar spot includes small, bleached round spots on the turfgrass ranging between 5–6 inches in home lawns. The disease also converts the color of the grass to a tan-ish color that looks similar to straw, compromising its overall natural look and luster. You may find these dollar spots on a wide variety of turfs.
There are a few symptoms of the dollar spot disease that homeowners should keep an eye for.
There is no fixed size for dollar spot in your lawn, however, they are closer to a coin size in most cases—hints its name. As previously mentioned, the typical size of dollar spot-damaged areas in your turf are usually 5–6 inches. However, this may also be greater depending on specific turf conditions.
The leaf blades affected from the disease usually have an upright appearance that are white or pale in color. The lesions change color with reddish-brown margins.
The tips of the leaves begin to die after becoming girdled on the surface, which is the clearest indicator of dollar spot disease in turfgrasses. However, you may not see this in closely cut turfgrasses. Instead, the leaves may become white or tan on the tips. The turfgrass starts dying in these spots until it spreads throughout the lawn. Some homeowners may also see short, fuzzy, mycelium forming on the turf. This increases when the morning dew is present and starts contributing to the disease.
Pictured above: Mycelium on turfgrass.
With that being said, the best way to officially diagnose dollar spot in your lawn is by sending a sample in to your local extension service office.
Brown Patch vs. Dollar Spot
Some people often mistake brown patch disease for dollar spot and vice versa. However, both are different with their particular solutions. While both diseases are caused by an invasive fungus, their conditions are different.
For instance, brown patch, or Rhizoctonia solani, includes brownish-yellow “patches” that can spread through the surface of turfgrass if not controlled properly. Brown patch may start at a few inches (usually around 6 inches) but can spread as much as several feet if you do not take steps to treat it.
Brown patch becomes more severe during warmer weather in the U.S. Similarly, high humidity levels can also cause this disease to escalate.
Dollar spot has smaller spots on the ground. Similarly, these turf patches are perfectly circular making them different from a brown patch.
However, it can be a little difficult for some homeowners to understand the difference between the two. The best way to identify any type of disease is by sending a sample in to your local extension service office.
Pictured above from left to right: Brown patch and dollar spot. Although the diseases in the images above look different, both brown patch and dollar spot can appear in different shapes and sizes.
What causes dollar spot?
We talked about what the disease is and what its symptoms look like. However, there are a few factors that impact the development of the disease.
The biggest cause for dollar spot is a change in the weather conditions, and as a result, soil conditions in your lawn. The infestation levels are much higher in the spring season as compared to other times of the year. However, temperatures need to exceed a particular barrier for this.
Temperature is a key player in dollar spot development in turfgrass surfaces. The growth of dollar spot increases during higher temperatures. While exact temperatures vary, a temperature range higher than 50o F is a must.
As mentioned in our Lawn Disease Control article, dollar spot also requires a particular level of moisture for the pathogen to spread. This period ranges between 10–12 hours of consistent leaf wetness in most cases. Combined with cool nights, excessive periods of moisture can surely contribute to dollar spot outbreaks.
The type of nutrition grasses receive affects the overall strength and resistance against dollar spot for most lawns. Lawns with a lower level of potassium usually have poor tolerance against dollar spot disease and can easily get infected.
Drought conditions impact the turf negatively, which can increase the growth of dollar spot in a lawn as well. In other words, lawns that have been weakened by some other external stressor become more susceptible to disease outbreaks in general.
Excessive Thatch and Frequent Irrigation
Extra thatch buildup and excessive irrigation can make it harder for the turfgrass to stay healthy. Both factors block out the turf’s ability to absorb nutrients and contribute to turf diseases like dollar spot. Conduct an irrigation audit to make sure your lawn is receiving the proper amount of water.
Pictured above: Thatch in turfgrass
When does dollar spot appear in lawns?
As stated in NC State Exention’s article on dollar spot, “Dollar spot usually infects grasses in the spring when night temperatures exceed 50°F, even though symptoms of the disease may not appear until later in the spring or early summer.”
What types of grass does dollar spot affect?
You may find dollar spot on a wide variety of turfs. However, dollar spot is most commonly found in smaller-length turfgrasses, or grasses that are usually maintained at a shorter height. Dollar spot has a diameter of 5–6 inches depending on the severity of the diseases in grasses kept at heights lower than 1 inch. You can also find dollar spot on longer-length grasses (like most lawns).
Some grass types may be at a higher risk of developing dollar spot. For instance, bentgrass, perennial ryegrass, Kentucky bluegrass and bermuda grass are the most common grass types for dollar spot outbreaks.
How do I treat dollar spot?
Following are some common preventive measures and treatment options that homeowners should consider while taking care of their lawn.
Cultural Control of Dollar Spot
- Avoid Cutting the Grass Too Short: Shorter grass has a higher probability of contracting dollar spot disease. Therefore, homeowners should not cut their grass too finely. Learn more about your grass type’s ideal mowing height here. Avoid cutting your grass at a height less than 1 inch.
- Irrigate Turf Timely: Irrigation patterns in your turfgrass impact the propagation and growth of pathogens on the grass. Therefore, avoid over-irrigating the turf surface because it can lead to further fungal growth. Consider conducting an irrigation audit.
- Keep the Lawn Clean: Thatch growth and concentration can prevent necessary nutrients from reaching the soil. Therefore, ensure you keep your lawn clean and maximize aeration in the grass for better growth and cycle.
- Add Fertilizer: You already understand how malnutrition impacts dollar spot. Therefore, try using a fertilizer with more potassium in it to keep your soil free from dollar spot.
- Use Soil Test Results: You can always run soil tests if you aren’t sure what your turf lacks. These tests provide a comprehensive report and help lawn owners come up with the best mode of action for solving the dollar spot condition. Learn more here.
Sod Solutions recommends the Lawnifi® Fertilization Program. Lawnifi gives your lawn what it needs in the form of nano-sized nutrients, exactly when it needs it in the form of easy-to-apply monthly applications from March to November.
It’s important to note that even with the use of an improved fertilizer program, timely applications of fungicide are still necessary for overall lawn health. If you fertilize your lawn with nitrogen before applying a fungicide and presently have a fungus, that fungus will expand exponentially, which can be disastrous for your lawn.
Chemical Control of Dollar Spot
If dollar spot has already occurred in your lawn, the next step is finding the proper treatment. Although applying dollar spot fungicide can be slightly challenging, it is definitely effective for controlling the disease in your lawn.
What is the best fungicide for dollar spot?
When searching for the best disease control for dollar spot, there are many options to consider. For best results, you may consider using chlorothalonil, fluoxastrobin or azoxystrobin for controlling dollar spot in your lawn. These fungicides are available in brands such as Fame and Heritage. Armada 50 WDG is also an effective disease control product for dollar spot. Follow label instructions properly.
How do I prevent dollar spot?
While disease control products are generally used for fixing diseases like dollar spot in your lawn, they can also be used to prevent diseases from occurring in the first place. Apply one of the products above at a preventive rate during the spring or fall if you’ve had dollar spot before. Apply at a preventive rate in the late spring to prevent disease outbreaks in the summer for cool season turf.
Be wary of the disease becoming resistant to applications of the same chemical if you apply disease control multiple times. Consider rotating fungicides with differing active ingredients to keep this from happening. Learn more here.
Because applications vary with different grass types, it’s important to follow the label’s directions precisely. Generally, fungicide applications take place in 14–28 day intervals, although the time of year for application may differ among cool season and warm season turfgrasses.