You thought those tan spots on the lawn would go away on their own, but they just keep getting bigger. If your lawn is suffering from dollar spot, ignoring the problem won’t help your grass combat this turfgrass disease. But here’s the good news: All it takes is a little TLC to restore your lawn back to health and control dollar spot.
What is dollar spot, and how do you get rid of it? We’ll help you understand the lawn disease so you can defeat it and help prevent future infections.
How to identify dollar spot
The causal agent of dollar spot lawn disease is Clarireedia jacksonii (formerly Sclerotinia homoeocarpa). The pathogen will infect your lawn when it finds the right turfgrass host and the environmental conditions are in its favor.
When tan spots 2 to 6 inches in diameter are popping up in your lawn, it may be a case of dollar spot. The circular patches are typically the size of a silver dollar, which is where the disease gets its name.
If you ignore the disease and don’t implement treatment right away, the spots will spread and merge to create large areas of dead grass. Delaying dollar spot treatment might be the more tempting option, but you’ll only have more work to do in the future.
Keep in mind that many other lawn diseases also appear as dead patches of grass. For more accurate identification, take a look at the grass blades. Grass blades affected by dollar spot have hourglass-shaped lesions with bleached centers and reddish-brown to purplish borders. As the lesions expand, the leaves are girdled and begin to slowly die.
Another way to identify dollar spot is to inspect the affected areas for a cobweb-like coating. The material is called mycelium and it has a silvery appearance (another reason why the ‘silver’ dollar spot name is so fitting). The best time to look for the mycelium is in the morning when dew is present.
What grass types are susceptible to dollar spot?
Turfgrass falls under two categories: warm-season and cool-season grass. Unfortunately, all species of warm- and cool-season grasses are susceptible to dollar spot.
So whether you grow warm-season zoysiagrass or cool-season Kentucky bluegrass, your grass is susceptible to the disease.
What causes dollar spot?
For a turfgrass disease to develop in your yard, the right environmental conditions must be in place. Most fungal diseases thrive in lawns that are poorly managed and when the weather conditions are just right.
Let’s take a look at the various environmental factors that encourage dollar spot growth:
- Dollar spot is most severe in lawns with low nitrogen levels, low mowing heights, and dry soils.
- Dollar spot symptoms typically occur late spring to early summer when temperatures are between 60 and 90 degrees.
- The pathogen thrives when days are warm, nights are cool, and dew is heavy.
- Dollar spot symptoms also may occur in early to mid-fall when days are warm and nights are cool.
- The disease favors high humidity and long periods of leaf wetness, about 10 to 12 hours long.
- Excessive thatch and leaving wet autumn leaves on the lawn can encourage dollar spot.
How does dollar spot spread?
Even when you don’t see small patches in your yard, dollar spot could already be infecting your lawn. How? The fungus survives unfavorable conditions as dormant mycelium in infected grass.
The disease spreads across the lawn via lawn mowers, lawn equipment, infected grass clippings, shoes, wind, water, and animals.
How to get rid of dollar spot
Spraying your lawn with fungicides might seem like a quick solution, but relying on chemicals alone won’t produce the results you want. Fungicides may offer temporary results, but if you’re not changing the environmental factors that encouraged the disease in the first place (such as excess thatch or poor irrigation), then the disease will continue to persist.
If you want to get rid of dollar spot for good, then you’ll need to rely heavily on healthy lawn care routines. Fungicides can help play a role in the treatment regime, but they shouldn’t be the only disease control method you take.
Another reason fungicides aren’t a reliable solution is that dollar spot quickly develops resistance to fungicides, including benzimidazole and DMI fungicides.
When using a fungicide to prevent further dollar spot infection, combine it with the following lawn care treatments:
- Apply a compost top dressing over the lawn. Compost has been shown to reduce dollar spot severity by increasing the soil microbe population.
- Apply adequate nitrogen fertilizer (remember, dollar spot flourishes in lawns with low nitrogen).
- Remove thatch with a verticutter or power rake.
- Correct your irrigation regime. Watering deeply and less often promotes a robust root system, while watering for short periods too often encourages a shallow root system. Water in the early morning (before 10 a.m.) so the lawn can absorb the moisture before the afternoon sun evaporates it.
- Mow the lawn regularly. Overgrown grass is attractive to disease and pests. Never cut off more than ⅓ of the leaf blade at a time; otherwise, you will stress your turf and make it more susceptible to disease.
How to prevent dollar spot
The best way to prevent any lawn disease from growing in your yard is to keep your lawn well maintained. Skipping the weekly mows, allowing thatch to build up, watering too late in the day –– these cultural practices will create a breeding ground for grass fungi, including dollar spot.
If you don’t want to deal with the headache of lawn disease, here are 15 lawn care treatments that encourage a healthy and robust lawn:
- Remove leaves and other debris from the lawn. Fungus loves to overwinter in debris and take hold of your yard come springtime.
- Mow the grass regularly (and correctly). Remember, don’t cut more than ⅓ of the grass blade during a single mow. Cutting too much at once will stress and weaken the turf.
- Leave behind grass clippings. When your grass is infected with a fungal disease, you don’t want to leave grass clippings behind (otherwise, the infection may spread). But it’s good for your lawn to leave the grass clippings behind when the lawn is healthy. A layer of grass clippings acts as mulch by retaining moisture and adding nutrients to the soil.
- Perform proper irrigation practices. Create a watering regime where you’re able to water the lawn less often but for long periods. This watering technique encourages a strong root system. Avoid watering your lawn in the evening; otherwise, the grass may cling to the grass blades at night and invite pests and disease. It’s best to water the lawn before 10 a.m.
- Invest in a sprinkler system. Sprinkler systems apply uniform water levels across the yard and are designed to meet your lawn’s specific moisture needs. A sprinkler system takes the workload off your shoulders while giving your grass just what it needs.
- Plant grass seed that’s disease-resistant and suitable for your lawn. Don’t make the mistake of growing warm-season grass where winters are long and ice cold. Talk to a lawn care professional about the best type of grass to grow in your area and which varieties are the most disease-resistant.
- Test your soil and add amendments. If you want healthy grass, you’ll need to have healthy soil, too. Perform a soil test to determine what amendments and nutrients it may be missing.
- Fertilize your grass. Many diseases require lawns to have imbalanced nutrient levels. Maintain your lawn’s vigor by fertilizing it at least once a year.
- Aerate compacted soil. Compacted soil prevents water, oxygen, and nutrients from accessing the roots. Aeration relieves compacted soil by creating small holes in the ground.
- Remove thatch that exceeds ½-inch thick. Thatch is the buildup of dead organic matter that accumulates between the soil and turf. A thick thatch layer becomes a breeding ground for pests and disease.
- Overseed the lawn. Keep your grass green and dense by overseeding the yard once a year. It’s a good idea to overseed with a disease-resistant cultivar if you can.
- Remove existing weeds. Weeds compete with your lawn for nutrients, space, light, and moisture. If a weed invasion takes over your yard, your turf may weaken. Remove existing weeds by hand-pulling them or applying a post-emergent herbicide.
- Apply pre-emergent herbicide. You can help prevent invasive weeds from growing by applying a pre-emergent herbicide.
- Control grubs and other pests. Grubs live just underneath the soil’s surface, and they can weaken your turf by feeding on its root system.
- Spread a ½-inch layer of compost across the lawn. Compost is a nutritious soil amendment. You can spread a compost top dressing with a rake or brew a compost tea and spray it on the lawn.
Chemical control: Fungicides for the lawn are most valuable when applied as a preventative measure. Most fungicides are not effective against lawn disease as a curative treatment.
What if I can’t identify the fungus?
Some grass diseases have similar symptoms, making it difficult to determine which one is growing in your yard. If you misidentify the fungus, then your treatment methods might prove futile.
Contact a diagnostics lab or a turfgrass pathology lab when you’re having trouble identifying the fungus in your yard. These labs specialize in diagnosing turfgrass disease and are typically located at state universities.
What other grass diseases can infect my lawn?
Dollar spot isn’t the only lawn fungus that can turn your grass from green to tan. And tan isn’t the only color your lawn might turn. Various fungal diseases can infect your turf, including:
- Anthracnose
- Brown patch
- Fairy ring
- Gray snow mold
- Leaf spot and melting-out
- Pink snow mold
- Powdery mildew
- Red thread
- Rust
- Summer patch
Got grass fungus? Turn to the pros
No one wakes up on a Saturday afternoon and thinks, “I’m so excited to remove fungus from my yard today.” Sure, you’re excited for the fungus to be gone, but chances are good you’re not keen on doing the work to make it disappear.
When dollar spot invades your lawn, hire a local lawn care professional to treat the turfgrass disease for you. Even better, employ a lawn care professional year-round so that you never have to worry about lawn care again. Your yard will thank you for it (but the fungus certainly won’t).
Main Photo Credit: Scot Nelson | Flickr | CC0 1.0
