Learning Center / Lawn problems
What causes lawn disease, and how do you prevent it?
Fungus, fed by hot days, warm nights and humid air. Mowing tall with sharp blades, watering in the early morning and a preventive program from May to September keep most of it away. Grass it kills has to be reseeded.
- By David Obeid, founder
- Reviewed
- 6 min read
The short answer
Why do lawns get disease in summer?
Lawn diseases are fungi, and Northern Virginia summers give them exactly what they need: hot days, warm nights and humid air. Grass that stays wet for long stretches, especially overnight, is where they get started.
Tall fescue is the right grass for this area, but it is especially prone to brown patch. A thick, healthy lawn handles disease far better than a thin, stressed one.
What to look for
What do the common lawn diseases look like?
These are the diseases our prevention program targets.
| Disease | What it looks like | When it shows up |
|---|---|---|
| Brown patch | Tan, roughly circular patches that can spread quickly | Hot, humid stretches with warm nights |
| Dollar spot | Small, straw-colored spots, roughly the size of a silver dollar, that can merge | Warm days with heavy morning dew |
| Red thread | Pinkish-red, thread-like growths on the grass blades | Cool, wet weather in spring and fall, often on underfed lawns |
| Leaf spot | Small brown or purplish spots on the blades that can thin the lawn | Cool, wet weather |
Prevention
What habits help prevent lawn disease?
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Mow tall
Keep fescue at about 3.5 to 4 inches. A stressed, short lawn shows disease damage faster.
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Keep blades sharp
Dull blades tear the grass, and torn tips give disease a way in.
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Mow dry grass
Mowing wet grass can carry disease from one part of the lawn to another.
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Water early in the morning
Deep, infrequent watering early in the day lets the grass dry off. Evening watering leaves it wet all night.
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Go easy on spring and summer fertilizer
Heavy feeding at the wrong time pushes soft growth that disease loves. Fescue's main feedings belong in fall.
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Keep leaves and debris off
Anything that sits on the grass and holds moisture against it raises the risk.
Treatment
Does a lawn disease program work?
Yes, as prevention: it lowers the risk and the damage, but it can't bring back grass that has already died. Our disease prevention program is five applications spaced about three weeks apart, from around May into September, starting at $54.15 a visit. It is added to a lawn care program and included in the Lifesaver plan.
If your lawn had brown patches last summer, the time to start is before May, not after the patches show up. Weather still drives disease, so even a protected lawn can get some in a bad year.
Recovery
Will a lawn recover from disease on its own?
Lightly damaged grass often recovers when the weather cools, but grass that has died will not grow back. Tall fescue doesn't spread to fill gaps, so dead patches need new seed.
Early fall aeration and overseeding is the best way to fill disease damage back in. How to tell disease from heat stress.
Related questions
What people also ask
What is brown patch?
A fungal lawn disease that shows up as tan, roughly circular patches in hot, humid weather. It is the most common summer disease in tall fescue lawns like the ones across Northern Virginia.
How many disease applications are there, and when?
Five applications, about three weeks apart, starting around May and running into September.
Will it fix brown spots I already have?
The program is preventive. Grass that has already died needs to be reseeded, and fall aeration and overseeding is the best way to fill those areas back in.
Do I need a fertilization program too?
Disease prevention is an add-on to lawn care. A well-fed lawn on a regular fertilization and weed control program is also better able to handle summer stress.
Keep reading
More from the Learning Center
- How do you get rid of lawn weeds and keep them out? Pre-emergent versus post-emergent, why crabgrass timing follows soil temperature, and why a thick lawn is the best weed control there is. Lawn problems · 6 min read
- How can you tell if your lawn is compacted? The warning signs of compacted clay soil, why it happens so often in Northern Virginia, and what actually fixes it. Lawn problems · 4 min read
- Should you renovate your lawn with sod or fix it with treatments? How to tell whether your lawn needs new sod or can be brought back with seeding and a lawn program, what each costs, and how long each takes. Lawn problems · 6 min read
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