How to Identify 5 Common Lawn Diseases

Lawn diseases can be frustrating for homeowners. A healthy, green lawn takes work to maintain, so seeing brown spots, dead patches, or fungus take over is disheartening. Understanding the most common lawn diseases will help you identify them early and treat them quickly, restoring your lawn’s appearance. We will describe how to identify the five most widespread lawn diseases and provide tips for treatment and prevention. With proper care and attention, you can get your lawn looking lush and green again.

Symptoms of Lawn Disease

Before jumping into the specifics of each type of lawn disease, it’s helpful to understand some of the general symptoms that may indicate your lawn is suffering from a problem:

Discolored or dead grass – This includes brown, yellow, or orange spots or patches in your lawn. Fungal diseases often cause grass blades to turn yellowish or brown.
Mushrooms/fungus – Particularly after rain or heavy watering, mushrooms or puffballs growing in your lawn can indicate fungus or disease.
Unusual patterns – Some diseases cause grass to die in circles or rings, while others create patchy, irregular patterns. Strange or asymmetric patterns to dead grass or growth can signify disease.
Thinning grass – If your lawn looks less dense than usual or has large bare patches, it could be suffering from an infestation or disease.
Poor growth – Grass that is diseased stops growing normally and quickly. You may notice slower than usual growth after mowing.
Excess moisture – Wet, soggy soil and excessive lawn moisture provide the perfect breeding ground for fungi and disease.

Keep an eye out for these general symptoms. Pay extra attention after rain or watering, as excess moisture increases the likelihood of diseases occurring. Next we’ll cover how to diagnose specific lawn diseases.

Brown Patch

Brown patch is one of the most prevalent lawn fungal diseases in the United States. As the name suggests, this disease creates scattered brown patches of dead or dying grass across the lawn. Here is how to identify brown patch disease:

How to Recognize Brown Patch:

Circular brown spots ranging from a few inches to a couple feet across.
Patches have dark brown borders that slowly expand over time.
Morning dew accentuates the spots, making them more visible.
Often occurs in hot, humid weather in mid to late summer.
More likely to develop in tall, thick, and excessively fertilized lawns.

How to Confirm Brown Patch:

Examine grass blades closely to spot grayish-white fungal mycelium with dark brown spores on the crowns and stems.
The fungal growth causes the grass blades to turn yellow or brown and die.
Healthy grass can easily be pulled away from the fungal areas.
The fungus spreads rapidly under adequate moisture and temperature.

Treatment for Brown Patch:

Improve drainage and reduce watering to dry out the lawn as much as possible.
Avoid excess nitrogen fertilization which encourages brown patch growth.
Let grass grow slightly longer (3-4 inches) to reduce moisture buildup at base.
Apply fungicide containing one of the following active ingredients: azoxystrobin, myclobutanil, propiconazole, pyraclostrobin, or triticonazole.

Prevention of Brown Patch:

Maintain proper fertilization and soil pH levels.
Water deeply but infrequently in early morning.
Allow grass to dry thoroughly between watering.
Promote airflow by avoiding lawn thickets.
Rake up fallen leaves, debris, and thatch to reduce dampness.
Apply preventative fungicide treatments in early summer before disease onset.

So in summary, look for the characteristic brown circular patches that expand outward and examine grass closely to spot grey fungal mycelium in order to diagnose brown patch fungus. Promoting proper lawn care and growth conditions can help prevent this disease.

Dollar Spot

Dollar spot is another very common fungal infection that impacts lawns across the United States. Identifying it early is key, as it can severely damage grass when left untreated. Here is what to look for:

How to Recognize Dollar Spot:

Small brown spots typically no larger than 2 inches wide.
Spots are round to oval shaped, sometimes with distinctive yellow rings around them.
Patches often merge together creating larger dying areas as disease spreads.
Mainly impacts low-cut, heavily watered lawns in warm, humid weather.
Most active from spring through early fall.

How to Confirm Dollar Spot:

Inspect grass closely to reveal tan, dried lesions with ashen white centers on individual blades.
Can see cottony, cobweb-like fungal mycelium early in the morning on infected areas.
Tufts of grass can detach easily from fungal spots.
Does not spread in uniformly circular patterns like some other diseases.

Treatment for Dollar Spot:

Reduce watering frequency and improve lawn drainage.
Apply high nitrogen fertilizer to help grass recover and fill in bare spots.
Mow with sharp blades to avoid stressing the grass.
Rake vigorously to remove debris and break up fungus.
Apply fungicide containing chlorothalonil, propiconazole, myclobutanil, or thiophanate-methyl.

Prevention of Dollar Spot:

Allow grass to grow slightly taller and cut less frequently.
Water deeply and less often early in the day.
Avoid excess nitrogen fertilization which encourages dollar spot.
Reduce thatch buildup through aerating, dethatching, or topdressing with compost.
Use fans or air circulation tools preventively to reduce humidity at lawn level.
Apply preventative fungicide treatments starting in early spring.

In summary, look for the small brown spots with yellow rings that appear in warm, humid weather. Examining the grass closely reveals lesions and fungal mycelium. With proper lawn care and preventative fungicides, dollar spot can be avoided.

Gray Leaf Spot

Gray leaf spot is a foliar disease that impacts many grass types, including perennial ryegrass, St. Augustine grass, and tall fescue. This disease thrives during hot, humid, wet weather. Here is how to identify gray leaf spot:

How to Recognize Gray Leaf Spot:

Roughly rectangular lesions approximately 1/4-1/2 inch long on grass blades.
Lesions are tan, brown, or purple bordered by yellow or chlorotic tissue.
Lesions run parallel to the veins giving a characteristic stripe pattern.
Leaf spots merge and increase in number over time.
Causes significant thinning of the lawn as disease worsens.

How to Confirm Gray Leaf Spot:

Inspect grass closely to reveal lesions with oval gray spots containing fungal spores.
Brush hand back and forth across grass to reveal increasing amounts of dead tissue and lesions.
Can pull grass out easily from areas infected by the fungus.
Most severe during peak summer heat on perennial ryegrass, St. Augustine grass, and tall fescue.

Treatment for Gray Leaf Spot:

Improve lawn drainage and reduce irrigation.
Apply fungicides containing azoxystrobin, myclobutanil, propiconazole, or chlorothalonil.
Bag clippings after mowing to prevent spread.
Rake vigorously to remove debris and infected grass.
Re-seed affected areas to fill in bare spots.

Prevention of Gray Leaf Spot:

Water early in day to allow grass to dry thoroughly.
Avoid over-fertilizing lawns unnecessarily.
Promote airflow and thin grass by removing debris and lawn thickets.
Apply preventative fungicide in early summer or when disease first spotted.
Plant resistant grass varieties like fine fescue or zoysia grass.

To summarize, look for the characteristic rectangular tan or purple lesions running along the grass blade veins. Thinning grass and oval fungal spots confirm gray leaf spot infection. Proper mowing, watering, and preventative fungicides can help avoid this disease.

Powdery Mildew

Powdery mildew is easy to identify from its characteristic white, powdery coating on grass leaves. This is another foliar fungal disease favored by shade and high humidity. Here are the symptoms:

How to Recognize Powdery Mildew:

White to grayish powdery growth on surface of grass blades.
Can appear blotchy, in circular patches, or uniform across affected areas.
More severe on shaded, enclosed areas of lawn.
Impacts all grass types but is most common in tall fescue and perennial ryegrass.
Worsens in cooler weather with high humidity and low sunlight.

How to Confirm Powdery Mildew:

Rub fingers over grass blades to reveal a white chalky residue.
Use a magnifying glass to inspect powdery areas and see fungal structures and spores.
Look for yellowing or browning leaves as the disease advances.
Plant and soil test to verify optimal pH and nutrients are present.

Treatment for Powdery Mildew:

Apply fungicides containing chlorothalonil, myclobutanil, propiconazole, or triadimefon immediately at first signs.
Increase sunlight exposure and airflow circulation in affected areas.
Avoid excessive shade and moisture on the lawn.
Cut grass no shorter than 3 inches to reduce humidity at base.

Prevention of Powdery Mildew:

Select resistant grass varieties like fine fescues or Bermuda grasses.
Reduce nitrogen fertilization and improve drainage.
Water in early morning to allow grass to dry out during day.
Remove lawn debris, leaves, and dense thicket areas.
Apply preventative fungicides when disease is common in your area.

In summary, the white powdery coating on grass is the most obvious sign of powdery mildew. Improving lawn growing conditions and applying timely fungicide treatments can help prevent and control this disease.

Red Thread

Red thread gets its name from the characteristic red or pink fungal threads it produces. It thrives in wet, acidic lawns low in nutrients. Here is how to spot red thread:

How to Recognize Red Thread:

Presence of cottony/hair-like pinkish red threads among grass leaves when wet with dew.
Reddish fungal threads wrap around leaf blades and across the lawn.
Blades of grass appear watersoaked, dull green, or yellowish between red filament strands.
Dieback of circular patches or across large areas of the lawn.

How to Confirm Red Thread:

Early morning inspection reveals red filaments stretching between grass blades.
Microscopic examination shows thin hyaline hyphae with clamp connections.
Primarily impacts northern cool-season turfgrasses like fine fescues.
Worst on acidic, wet, underfertilized lawns.

Treatment for Red Thread:

Reduce lawn moisture by improving drainage and watering early in day.
Increase mowing height to 3 inches to reduce humidity at base.
Apply nitrogen fertilizer to improve grass growth and fill in bare patches.
Adjust pH to neutral level around 7.0 if acidic.
Apply fungicide containing chlorothalonil, mancozeb, myclobutanil, propiconazole, or thiophanate-methyl.

Prevention of Red Thread:

Maintain optimal fertilization, mowing, watering, thatch control, and pH practices.
Allow grass to dry fully between watering and after rain or dew.
Reduce shade and improve lawn air circulation.
Apply preventative fungicide treatments in spring and fall.
Purchase red fescue cultivars specifically bred for disease resistance.

In summary, look for the characteristic pinkish red filaments across dew covered grass to identify red thread fungus. Maintaining optimal turf growing conditions and timely fungicide use provides effective prevention.

How to Prevent Lawn Diseases

While fungicides play an important role in treating active lawn disease infections, the best approach combines chemical treatments with optimal lawn care practices to prevent diseases proactively. Here are the top tactics for preventing lawn disease issues:

Promote Healthy Grass Growth

Maintain proper mowing height for your grass type, never cutting off more than 1/3 total blade length.
Follow seasonal fertilization schedule to keep grass actively growing.
Dethatch and aerate annually to alleviate soil compaction.
Overseed thin or bare areas to maintain dense turf.

Reduce Excess Moisture

Water deeply but as infrequently as grass can tolerate.
Allow grass to dry fully between watering.
Improve drainage through grading, aerating, or amendments.
Avoid frequent late-day watering.

Modify Local Environment

Prune trees/shrubs to increase sunlight penetration.
Use fans or air circulation tools to reduce humidity.
Remove lawn debris, leaves, and dense thickets regularly.

Apply Preventative Fungicides

Use fungicide treatments at disease-prone times of year as a preventative.
Rotate chemical modes of action annually to avoid resistance.
Always follow label directions carefully.

Choose Disease Resistant Varieties

When establishing a new lawn, select grass types or mixes bred for disease resistance.
Fine fescues, Bermuda grasses, and zoysia offer good disease resistance.

Healthy grass is less susceptible to diseases. By combining good agronomic practices with preventative fungicide applications, lawn diseases can be avoided and controlled without significant damage. Be sure to properly identify the specific disease at hand, then apply integrated treatment and prevention methods for the best results. With proper lawn care, your grass can thrive disease-free all year long, keeping your landscape green and lush.

Frequently Asked Questions About Lawn Diseases

What are the first signs my lawn may be suffering from a disease? The earliest signs of lawn disease include thinning grass, reduced growth, yellowing or browning grass blades, and the appearance of mushrooms or puffballs. Strange patterns, rings, or patches of dead grass can also indicate disease.
What causes lawn diseases? Lawn diseases are most often caused by fungal infections. Excess moisture, shade, poor drainage, and low sunlight all create optimal conditions for fungal growth. Diseases also thrive when grass is stressed from improper mowing, fertilization, or improper pH levels.
When are lawns most prone to disease issues? Most lawn fungal diseases peak in summer or early fall when humidity is high. Spring and fall are also common times for disease problems. Extended wet weather increases disease likelihood. Milder diseases like powdery mildew occur in cooler weather.
How can I tell the difference between lawn disease types? Carefully examining the grass for patterns and lesions along with microscopic inspection of fungal structures can help identify specific diseases. Send samples to extension labs for definitive diagnosis if unsure.
Should I use fungicides preventatively or only after seeing disease? Applying preventative fungicide treatments at peak disease seasons is ideal to protect vulnerable grass. However, follow up applications are needed after disease appears to fully treat existing infections.
How long does it take for lawn diseases to kill grass? If left completely untreated, serious lawn diseases like brown patch can damage substantial amounts of grass within a week in peak conditions. Catching infections early allows grass to recover more quickly.
Will lawn diseases spread to my neighbor’s yard as well? Certain fungal diseases can spread via spores blowing from yard to yard. Following similar lawn care practices as your neighbor will help prevent spread. Proper mowing, watering, fertilizing, and fungicide applications should be coordinated.
If my lawn gets diseased, do I need to re-sod the entire yard? Catching lawn diseases early before extensive damage usually means grass can recover with proper treatment. Severely infected areas may need reseeding or spot sodding. Complete resodding is only necessary if the majority of grass is dead.
How can I prevent ever getting lawn diseases again after treatment? The best prevention is integrating optimal lawn care practices to promote healthy grass with preventative fungicide treatments before disease onset. Selecting disease resistant grass varieties, monitoring conditions, and addressing problems early also helps prevent major outbreaks.
What home remedies help cure lawn fungal disease? Home treatments like vinegar or baking soda solutions offer minimal benefits for serious lawn diseases. They do not provide the curative power needed once fungal infections have taken hold. Targeted fungicide applications based on the specific disease present are most effective.

Conclusion

Lawn fungal diseases are common issues for homeowners trying to maintain attractive, healthy lawns. The five most widespread lawn diseases are brown patch, dollar spot, gray leaf spot, powdery mildew, and red thread. Learning how to properly identify each disease through examination of symptoms and grass patterns is key so the right treatments can be applied at the optimal time. Catching infections early improves outcomes. Combining curative fungicide applications with good agronomic practices provides the best prevention and control. Paying close attention to your lawn and following the advice in this article will help you identify and conquer lawn disease problems quickly, restoring the lush curb appeal you desire.