A melting lawn might sound like something out of a horror movie, but if your yard is affected by leaf spot and melting-out, you may wake up to find your beloved grass has turned a ghastly yellow or blackish-brown.
Leaf spot and melting-out disease look similar, but these turfgrass diseases have some important differences. Read on to learn more about these troublesome fungal diseases and how to get rid of leaf spot and melting-out.
What Are Leaf Spot and Melting-Out?
Leaf spot and melting-out are both fungal pathogens that affect turfgrass lawns and golf courses. They can affect all parts of the plant, attacking roots, shoots, and leaves to cause decay that can spread rapidly and damage turf in large areas of your lawn.
These lawn diseases were originally thought to be one disease caused by the fungus Helminthosporium Plant biologists now recognize that these are two different diseases caused by different fungi. Melting-out disease is caused by the fungus Drechslera poae, while leaf spot is caused by Bipolaris sorokiniana.
Note: While leaf spot is unlikely to cause permanent damage, melting-out can kill turf if left untreated.
How to Identify Leaf Spot and Melting-Out
Leaf spot and melting-out typically resemble each other–– at first. The issue is, these two diseases can have very different outcomes, so it’s important to know which one you’re dealing with. Here’s how to determine whether you have leaf spot or melting-out disease.
Leaf spot symptoms:
- Browning and yellowing areas that spread through the yard
- Black or purple lesions on blades up close
- Appears in the summer
Melting-out disease symptoms:
- Resembles leaf spot at first, producing similar dark lesions on leaf blades and yellowing or browning turf
- Reddish-brown rotting as the disease escalates and spreads
- Appears in early spring, with rotting starting in April or May
Causes of Leaf Spot and Melting-Out Disease
Leaf spot and melting out can both survive in turf during typically unfavorable conditions, lying dormant over winter until temperatures climb above freezing. Combined with improper lawn care, when weather conditions are right, these diseases can appear and spread quickly.
Leaf spot and melting-out commonly attack Kentucky bluegrass, perennial ryegrass, and tall fescue. They’re both encouraged by these conditions:
- wet weather
- excess nitrogen fertilizer
- thatch buildup
- Low mowing height
- other sources of lawn stress
In addition to these conditions, melting-out tends to come out when there are cool temperatures, and has been observed appearing in weather as little as just above freezing. Leaf spot, meanwhile, needs warm evening temperatures and long periods of dew to take hold in your lawn.
How to Cure Leaf Spot and Melting-Out
If you’re looking to cure leaf spot and melting-out, it’s important to act fast. Both diseases can spread quickly, and when melting-out development progresses to turf rot, it becomes nearly irreversible. Luckily, there are many options available to treat leaf spot and melting-out disease.
If you’re facing an outbreak, these lawn care measures will help your lawn recover:
Mow Properly
If you’re struggling with leaf spot and melting out, mow your grass at the recommended height for your grass type, but no lower than 2 inches. Mowing lower than 2 inches may increase your turf’s vulnerability to the fungi.
Water in the Morning
Water grass deeply before 10 a.m., particularly in the summer months when leaf spot runs rampant. This will make sure your lawn soaks up all the hydration before the afternoon sun rises. Avoid watering in the evenings, as this will encourage damp conditions that lead to disease.
Water Less Often
Your lawn should only be watered when it needs to be. Water deeply and infrequently based on the needs of your grass type to make sure you’re nourishing the whole root system. Watering too often and for short periods encourages a shallow and weak root system.
Fertilize the Right Way
Apply fertilizer in only moderate amounts. Avoiding overfertilization won’t only protect your lawn from these troublesome diseases–– it’s better for your yard, your wallet, and for the environment long-term.
Overseed
Once a leaf spot infection spreads to the roots and crowns of grass, or when melting-out progresses to rotting, tending to the thinned turf that remains intact and overseeding with a resistant type of turfgrass is the only way to revive your lawn. Certain varieties of Kentucky bluegrass have been cultivated for resistance to these diseases.
Fungicides: A Last Resort
There are also several fungicides available that provide some control over leaf spot and melting-out. Proper timing is key to getting an effective result. For leaf spot, apply fungicide preventatively or in early stages of development. For melting out, apply fungicide before rotting begins.
These fungicide ingredients are recommended for use on leaf spot and melting-out disease:
- Iprodione
- Chlorothalonil
- Mancozeb
- Fludioxonil
- Azoxystrobin
- Penthiopyrad
Preventing Leaf Spot and Melting-Out Disease
In addition to practicing healthy lawn care habits, the best way to prevent leaf spot and melting-out disease is to plant resistant varieties of turf wherever possible. Several resistant cultivars of Kentucky bluegrass have shown promise against these diseases, while those that are prone to infection are likely to face recurring problems as the disease goes dormant and returns year after year.
If you have regular trouble with leaf spot, preventive application of fungicides can also help, but should be combined with healthy lawn care.
When to call a pro
When you’re dealing with a rapidly-spreading lawn disease like leaf spot or melting-out disease, it’s important to act as quickly as possible. These fungi won’t work with your schedule, but local lawn care pros are ready and willing to help whenever they’re needed.
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