If you notice tan spots on your lawn that just keep getting bigger, then your lawn may be suffering from dollar spot. But what is dollar spot, and how do you get rid of it? Ignoring the problem won’t help your grass combat this turfgrass disease.
All it takes is a little TLC to restore your lawn to health and control dollar spot. We’ll help you understand the lawn disease so you can defeat it and help prevent future infections.
What is dollar spot?
Dollar spot is a lawn disease that causes silver-dollar-sized spots of dead turfgrass, typically two to six inches wide. The pathogen, Clarireedia jacksonii (formerly Sclerotinia homoeocarpa), causes dollar spot lawn disease. It will infect your lawn when it finds the right turfgrass host and environmental conditions are in its favor.
How to identify dollar spot
Keep in mind that many other lawn diseases also appear as dead patches of grass. Grass blades affected by dollar spot have hourglass-shaped lesions with bleached centers and reddish-brown to purplish borders. As the lesions expand, the grass blades slowly die.
Another way to identify dollar spot is to inspect the affected areas for a cobweb-like coating. The coating is called mycelium, and it has a silvery appearance.
Pro tip: The best time to look for the mycelium is in the morning when dew is present.
How to get rid of dollar spot
Before you reach for the bottle of fungicide, the best way to prevent any lawn disease is to keep your yard well-maintained. Banish dollar spot and other lawn diseases for good with a proper lawn maintenance routine.
If you ignore the disease, 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.
Apply a fungicide
Fungicides can help treat dollar spot, but they aren’t the only solution you should rely on. If you’re not changing the environmental factors that encouraged the disease in the first place, then the disease will persist. 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:
Aerate the soil
Foot traffic and harsh weather can compact soil and prevent water, oxygen, and nutrients from accessing the roots. Aerating removes small cylindrical plugs of soil from the ground to relieve soil compaction. These small holes are about two to three inches deep and allow nutrients to reach the grassroots. There are two soil aeration methods:
- Core aeration: Also known as plug aeration, this method removes a core or plug of grass and dirt from the lawn.
- Spike aeration: This method involves poking holes into the ground with solid tines or a pitchfork.
Pro tip: The best time of year to aerate cool-season grasses is during the fall, while it’s best to aerate warm-season turf in the summer.
Apply compost
Compost is a nutritious soil amendment that reduces dollar spot severity by increasing the soil microbe population. Spread a ½-inch layer across your lawn with a rake or brew a compost tea and spray it on your lawn. You can make compost with materials, including:
- Fruit and vegetable scraps
- Coffee grounds
- Eggshells
- Straw
- Paper
- Cardboard
- Dry leaves
- Sawdust (not from treated wood)
Control grubs
Grubs are the larvae of several scarab beetle species and live just underneath the soil’s surface. They can weaken your turf by feeding on its root system, making it vulnerable to dollar spots. If you notice your grass is thin and turning brown, then you can take a shovel to the area and lift the soil to see if there are any white, soft-bodied critters living there. Control grubs with:
- Curative insecticides: Control an active infestation, and apply them in late summer.
- Preventative insecticides: Control newly hatched grubs from June to July.
- Nematodes: Microscopic worms provide natural grub control. Apply nematodes every two weeks until the infestation subsides, typically two to three times per season to prevent grubs from returning.
Dethatch
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 diseases like dollar spot Dense thatch also causes poor drainage and prevents herbicides, fertilizers, and insecticides from working by blocking access to nutrients, water, and oxygen.
You should remove thatch when it exceeds ½-inch thick with a verticutter or power rake. The optimal time to dethatch a cool-season yard is in the fall, while late spring through early summer is the best time to dethatch a warm-season lawn.
Fertilize
Many diseases require lawns to have imbalanced nutrient levels. If you want healthy grass, you’ll need to have healthy soil, too.
Perform a soil test to determine what amendments and nutrients your lawn is missing, and then fertilize your grass according to what the test results show your lawn needs. Dollar spot flourishes in lawns with low nitrogen, so you are likely going to need to use an adequate amount of nitrogen fertilizer to combat the disease.
Maintain your lawn’s vigor by fertilizing it at least once a year during your grass’s most active growing season. For cold-season grass, you should apply fertilizer during the early fall, and for warm-season grass, you should fertilize during the summer.
Irrigate
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. Avoid watering your lawn in the evening; otherwise, the water may cling to the grass blades at night and invite pests and disease.
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.
Mow regularly
Overgrown grass is attractive to disease and pests. Mow your grass regularly and correctly. Remember, don’t cut more than ⅓ of the grass blade during a single mow.
If you mow too low, you’ll scalp the lawn, making it difficult for your grass to get nutrients. Cutting too much at once will stress and weaken the turf. Make sure that your mower blade is sharp so that it doesn’t rip your grass.
Mulch with grass clippings
When your lawn is healthy, a layer of grass clippings acts as mulch by retaining moisture and adding nutrients to the soil. Mulching can help your landscaping stay healthy, and grass clippings are not only eco-friendly but free since you already have them available whenever you mow.
Layer one to two inches of clippings over the lawn and then wait for them to decompose before adding more as needed.
Mulching with grass clippings is only good as a preventative measure. Never leave diseased grass clippings behind, otherwise, the infection may spread.
Overseed
Overseeding is where you plant new seeds on top of your existing lawn. Keep your grass green and dense by overseeding your yard once a year with a disease-resistant cultivar. Don’t make the mistake of growing warm-season grass where winters are long and 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.
Early fall is the best time to overseed your cool-season grass, and you should overseed your warm-season lawn from the spring through early summer.
Remove weeds and debris
Fungus love to overwinter in debris and take hold of your yard come springtime. You should actively remove leaves and other debris from your lawn. It can be hard work, but it’s worth it.
Weeds compete with your lawn for nutrients, space, light, and moisture, making it vulnerable to disease. 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. To prevent invasive weeds from growing in the future, you should apply pre-emergent herbicide.
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.
The disease spreads across your lawn via your lawn mower, infected grass clippings, shoes, wind, water, and animals.
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 in the 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 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 spots.
FAQ about dollar spot
Which grass types are vulnerable to dollar spots?
Unfortunately, all species of warm-season 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 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
When dollar spot invades your lawn, hire a local lawn care pro to treat the turfgrass disease for you. With just a call or a click, you can employ a lawn care professional year-round so that you never have to worry about lawn care again.
Main Photo Credit: Scot Nelson | Flickr | CC0 1.0
