ASCOCHYTA LEAF BLIGHT
Also Known as Dollar Spot Fungus
Ascochyta Leaf Blight, often mistakenly referred to as Dollar Spot Fungus, is a minor stress fungus that can affect all turfgrass cultivars worldwide. Colorado’s hot and dry climate makes this lawn fungus particularly prevalent in the Boulder and Fort Collins areas.
Ascochyta Leaf Blight is most commonly observed when there is a rapid shift from cool, wet weather to hot, dry conditions. This common lawn issue typically arises sometime in late May or early June when temperatures rise quickly from 60’s and 70’s to 80’s plus.
Problems with Ascochyta Leaf Blight are more likely to occur in lawns with short grass roots. Shallow roots can result from poor watering practices, mowing the lawn too short, and inadequate cultural care. Typically, although not exclusively, Ascochyta is found in areas with poor sprinkler coverage or where little to no water is applied to the lawn. Lawns with deep-rooted grass are less susceptible to this minor lawn fungus.
Examples of Ascochyta Lawn Fungus
The Ascochyta lawn fungus can be recognized by the initial damage it causes to the center of the grass blades. In this picture, both the top and bottom of the grass blade remain green.
This lawn in Boulder, Colorado, is currently facing the challenges of Ascochyta Leaf Blight, a harmful fungus that thrives in lawns with shallow root systems. Addressing this issue responsibly will restore the health and beauty of your lawn while preventing further damage.
How to Prevent Ascochyta in Lawns
How to Identify Ascochyta Leaf Blight in a Lawn?
To properly identify Ascochyta leaf blight fungus, examine the newly infected leaf blades by getting on your hands and knees near the edge of the damaged area. Look for a blade of grass that is neither completely damaged nor entirely healthy. You will notice that this blade is collapsed, folded in half lengthwise, with a brown area starting in the center, while the top and bottom remain green. This results in a blade that has a green top, a brown center, and green bottom.
The key difference between Ascochyta leaf blight and Dollar Spot fungus is that Ascochyta does not have a dark band above the brown middle section, whereas Dollar Spot fungus does have this dark band. Aside from that distinction, there are no significant differences between these two common lawn diseases found in Colorado.
Generally, Ascochyta leaf blight causes only minor damage to lawns because it does not affect the crown of the grass blades. To address the lawn issue and prevent future fungus outbreaks, adjustments to the lawn’s watering schedule are necessary. It’s important to remember that Ascochyta is a symptom of a larger problem, often rooted in very short grass roots. Short roots typically result from shallow, frequent watering, which prevents roots from reaching deeper soil for water. Additionally, excessive watering can displace air in the soil, causing roots to remain shallow as they search for oxygen.
Although Ascochyta leaf blight and Dollar Spot fungus are often found in drought-stricken areas, the fungus can enter grass through damaged or cut leaf tips. It frequently utilizes water as a means of transmitting infection to new blades of grass, which is why we recommend waiting 24 hours after mowing before watering the lawn.
Ascochyta/Dollar Spot can be compared to a cold in humans: while anyone can catch a cold, healthier individuals are less likely to contract one. The same applies to turf grass. Lawns with deep roots, proper organic fertilization, aeration, deep and infrequent watering, correct mowing techniques, and strong, healthy soil conditions are far less likely to suffer from minor lawn diseases or fungi.
Grass roots should be about 6-12 inches deep into the soil. This core sample of a lawn with Ascochyta leaf blight shows the shallow roots in this lawn that are only about 2 inches deep.
Treatment Plan for Ascochyta or Dollar Spot
Treatment for Ascochyta caused by Shallow or Frequent Lawn Watering Practices
Expected Recovery in 7-14 Days
When the lawn watering is too shallow the lawn’s roots never dig deep because there isn’t any moisture deep in the soil.
The recommendations for Ascochyta Leaf Blight / Dollar Spot treatment, when the short roots are caused by poor sprinkler coverage or shallow and frequent watering are as follows:
- Adjust the watering schedule of the lawn to properly water the lawn deeply and infrequently. Ascochyta leaf blight / Dollar Spot fungus is a symptom of shallow grass roots. If the lawn was suffering from shallow and frequent lawn watering, the first step is to fix the broken sprinkler head and / or make adjustments to the watering schedule.
- To bring the lawn out of the stressed environment we recommend watering the lawn deeply for 3 consecutive days. After the three deep soakings, go back to a proper lawn watering schedule. Also, it is important to water early in the morning instead of late at night or even worse in the daytime.
- Perform two lawn aerations. One in the spring and one in the fall, to alleviate soil compaction.
- Apply Humate Soil Conditioner at any time of the year or at any time that the disease is active. Humate will increase the beneficial bacteria populations in the soil.
- Never apply synthetic pesticides (weed controls and lawn fungicides) to the infected area. Pesticides can hinder beneficial microbial activity in the soil, and microbial activity is essential to proper treatment of Ascochyta/Dollar Spot.
- Never mow the grass if it is wet, and always wait 24 hours after a mowing to water the grass. After a mowing the grass blades have been damaged. It takes 24 hours for a grass to repair the abrasion. If water is added to the lawn before the lesion has time to heal, the fungus can use the water as a transportation mechanism and infect new and otherwise healthy blades of grass.
Until the lawn fungus is eliminated, bag the grass in the infected area, increase the mowing height to 3” or 3.5”, and increase the mowing frequency so no more than 1/3 of the blade of grass is removed per mow.
Treatment Plan for Ascochyta caused by Overwatering Practices
Expected Recovery in 14-28 Days
If the lawn has short grass roots because it has been over watered, the grass roots are short because the water has replaced all the air in the soil. Since there is no air in the soil the roots will stay shallow because they are starved for oxygen.
The recommendations for Ascochyta Leaf Blight or Dollar Spot treatment, when the short grass roots are caused by severe over watering of a lawn:
- Adjust the watering schedule of the lawn to properly water the lawn deeply and infrequently. Ascochyta leaf blight / Dollar Spot lawn fungus is a symptom of shallow roots. If the lawn is suffering from too much water, the soil will be starved of oxygen and therefore the roots will stay at the surface looking for air. After fixing the watering it will take time and the lawn will need time to dry out so the roots to grow deeper.
- Perform two core aerations, one in the spring and one in the fall, to alleviate soil compaction.
- Apply Humate Soil Conditioner at any time of the year or at any time that the disease is active. Humate will increase the beneficial bacteria because it is a healthy food source full of beneficial organic matter.
- Avoid applying synthetic pesticides (chemical weed controls and lawn fungicides) to the area. Pesticides can hinder microbial activity, and microbial activity is essential to proper treatment of Ascochyta/Dollar Spot.
- Never mow the grass if it is wet and always wait 24 hours after a mowing to water the grass. After a mowing the grass blades have been damaged. It takes 24 hours for a grass to repair the abrasion. If water is added to the lawn before the lesion has time to heal, the fungus can use the water as a transportation mechanism and infect new and otherwise healthy blades of grass.
Until this lawn fungus is eliminated, bag the grass in the infected area, increase the mowing height to 3” or 3.5”, and increase the mowing frequency so no more than 1/3 of the blade of grass is removed per mow.
Photos Examples of Ascochyta Leaf Blight in a Lawn
This lawn in Fort Collins Colorado is suffering from Ascochyta Leaf Blight fungus, which is a mild stress fungus that can be easily fixed with a few adjustments to the sprinkler system.
This Ascochyta Leaf Blight in a tall fescue lawn in Arvada Colorado and you can see Ascochyta in a fescue lawn looks vastly different compared to a bluegrass lawn.
Ascochyta Leaf Blight fungus in a lawn in Louisville Colorado.
Lawn Disease Experts
Choose Organo-Lawn for expert lawn care you can trust! As a state-licensed company, we have a team of skilled professionals dedicated to resolving common lawn issues, including Ascochyta Leaf Blight Fungus and Dollar Spot Fungus. These lawn problems often plague the Boulder and Fort Collins areas, particularly during the summer months of June, July, and August. Let us help you achieve a lush, healthy lawn that stands out in your neighborhood!
We resolve lawn fungus issues by targeting the root cause rather than merely treating the symptoms.
Boulder / Longmont Area (303) 499-2000
Fort Collins / Loveland Area (970) 225-9425.
Ascochyta Leaf Spot and Dollar Spot Lawn Fungus FAQ’s
How to treat Dollar Spot without fungicides?
Dollar Spot should never require a fungicide to repair the damaged area of the lawn. Dollar Spot can be easily repaired by watering the damaged area deeply for three consecutive days and the returning to the 1-2-3-2-1 lawn watering technique.
Other lawn care services that might help with curing Dollar Spot leaf blight are to aerate the soil twice per year in the spring and fall. Humate soil conditioner does a great job at breaking up clay soils which allow grass roots to dig deeper.
What Causes Dollar Spot Fungus?
Most fungus problems occur from poor watering practices. Dollar Spot lawn disease is caused by improper lawn watering practices. Dollar Spot Fungus is a symptom of shallow grass roots typically caused by light frequent watering. The lawn fungus is often most noticeable in areas of poor sprinkler coverage. Dollar Spot Fungus treatment is fast and easy to remedy by correcting the sprinkler system coverage issue or improper lawn watering practices. After fixing the sprinkler system or improper lawn watering practices it is important to water the lawn for three consecutive days and then go back to the 1-2-3-2-1 lawn watering technique. The lawn will typically recover in 7-14 days.
Ascochyta leaf blight is a fungal disease that affects turfgrass, causing patches of brightly colored yellow grass. It primarily affects cool-season grasses like Kentucky bluegrass, perennial ryegrass, and fescue.
The disease is triggered by environmental stress, such as rapid changes in moisture, heat, or mowing stress. It often appears shortly after periods of cool rainy weather followed by a rapid change to hot and dry weather.
The disease causes leaf blades to dry out and turn tan or straw-colored, often with distinct lesions or discoloration starting at the center of the grass blades. Roots and crowns usually remain unaffected, allowing the grass to recover.
No, Ascochyta leaf blight is not usually fatal. The disease affects only the leaves, not the roots or crown, so the grass can recover with proper care and environmental improvement.
Ascochyta leaf blight effects lawns with shallow digging grass roots. To promote deep digging grass roots it is best to follow the 1-2-3-2-1 lawn watering practices, avoiding overwatering or irregular watering cycles, mowing at the correct height (3 inches or taller), and maintaining a sharp mower blade to reduce stress on grass.
The disease often resolves on its own with improved lawn care practices, such as consistent watering and reduced mowing stress. Fungicides are rarely necessary, as the disease is primarily stress-related. Humate soil conditioner applications can help recover the lawn quicker and help prevent future outbreaks.
Ascochyta leaf blight is most common during late spring and early summer when temperatures rise, and the lawn experiences sudden changes in temperature and moisture levels.
Yes, the fungal spores can spread through wind, water, or mowing equipment, but it will only spread to grass that has shallow digging grass roots.
No, but it can look similar. Ascochyta leaf blight causes leaf tips to turn straw-colored or tan, while drought stress typically affects the entire plant and occurs uniformly in dry areas.
Recovery time varies from lawn to lawn due to environmental conditions and soil conditions. Grass typically recovers within a few weeks after the stressors are alleviated and proper maintenance is implemented.