25 June 2026 · 7 min read
Dollar spot fungus: identifying and treating this lawn killer
Dollar spot creates silver-dollar-sized straw patches on lawns, especially in warm humid weather with low nitrogen. Here's how to confirm and treat it before it spreads.
Dollar spot is the fungus you notice when you walk out one morning and see dozens of small silver-dollar-sized straw patches scattered across the lawn. It hits warm humid mornings on lawns that are short on nitrogen and stressed by drought. The good news: dollar spot usually responds to a nitrogen feed alone — no fungicide needed. Here is how to confirm it and stop the spread before it merges into bigger dead zones.
What does dollar spot look like?
True to the name, dollar spot creates patches about the size of a silver dollar — roughly 1 to 2 inches across. The patches are bleached straw-coloured, almost white in the centre.
Two more clues to confirm dollar spot specifically:
- Hourglass lesions on individual blades. Pull a blade from the edge of a patch. You'll see a tan or straw-coloured band across the middle of the blade with brown edges. The shape narrows in the middle like an hourglass. Healthy green is above and below the lesion.
- White cobwebby mycelium in morning dew. Walk out early in the morning before the dew burns off. Dollar spot patches show fine white threads — like spider web — across the patch. The mycelium disappears once dew evaporates.
If you see both — hourglass blade lesions plus morning mycelium — it's dollar spot, confirmed.
When does dollar spot hit?
Dollar spot loves a specific set of conditions:
- Warm humid mornings. Daytime 70–90°F (20–32°C), nights cool enough for heavy dew.
- Low nitrogen. A lawn that's hungry is much more vulnerable.
- Drought stress. Stressed grass can't fight the fungus.
- Long dew periods. Damp leaves give the fungus time to colonise.
- Mowed too short. Shorter grass dries slower and stresses easier.
It hits cool-season lawns (Kentucky bluegrass, tall fescue, fine fescue, perennial ryegrass) and warm-season lawns (Bermuda, Zoysia) — basically every common North American lawn grass. Peak season is late May through September in most regions.
Dollar spot vs brown patch — don't confuse them
Brown patch is the other big summer fungus. It looks different and needs different treatment.
| Feature | Dollar spot | Brown patch |
|---|---|---|
| Patch size | 1–2 inches | 1–3 feet (and merging) |
| Patch shape | Small round | Large irregular circle, often with darker "smoke ring" edge |
| Blade lesion | Hourglass band, tan with brown edge | No clear lesion — whole blade dies |
| Morning mycelium | Fine white threads on the patch | Smoke-ring border of grey mycelium |
| Best fix | Nitrogen feed first | Fungicide, less water |
| Grass type | All cool-season + Bermuda/Zoysia | Tall fescue, Kentucky bluegrass, St. Augustine |
| Nitrogen response | Nitrogen helps | Nitrogen makes brown patch worse |
If you're not sure which one you have, look at patch size. Dollar spots stay small and discrete. Brown patch goes big fast.
The first-line fix — nitrogen
Here is the surprising part about dollar spot. A simple nitrogen feed is often enough to stop it on its own. No fungicide required.
Why? Dollar spot exploits hungry grass. A well-fed lawn grows faster than the fungus can spread, the new growth outpaces the damage, and existing patches green back over within a couple of weeks.
How to feed
Apply about 0.5 to 1 pound of nitrogen per 1,000 sq ft. Options:
- Quick-release nitrogen (urea-based fertilisers, Scotts Green Max). Works in days. Water in lightly after spreading.
- Slow-release nitrogen (Scotts Turf Builder, Milorganite, Vigoro All Season Lawn Food). Works over weeks but no burn risk.
Milorganite is a great call for dollar spot specifically — it feeds gently, has trace iron for colour, and won't push the soft growth that brown patch loves.
Watch the lawn for 7–10 days. In most cases dollar spot stops spreading and the patches fill in.
Cultural fixes — stop dollar spot from returning
If dollar spot keeps coming back every summer, fix the underlying conditions.
Water deeply, early morning
Dollar spot needs long leaf-wetness periods. Watering at night or in the evening keeps leaves wet for 10+ hours and creates fungus heaven.
Water early morning instead — between 4am and 9am. The lawn dries by mid-morning. Aim for 1 inch per week split across one or two deep soaks, not daily shallow sprinkles. Use a tuna can to measure.
Reduce thatch
Thick thatch holds moisture against the soil surface and creates a perfect humid environment for fungus. Dethatch in early fall with a power rake or core aerator. Keep thatch under 1/2 inch thick — push a screwdriver in and check the dead layer at the top.
Mow with sharp blades
Dull mower blades shred grass blades and leave ragged tears. Those wounds are the perfect entry point for fungal spores. Sharpen your blade in spring and again mid-summer. Replace it every couple of years.
Mow at the right height
Mowing too short stresses the lawn and dries it faster.
- Kentucky bluegrass: 2.5–3.5 inches (setting 4–5 of 7)
- Tall fescue: 3–4 inches (setting 5–6 of 7)
- Bermuda: 1.5–2 inches in summer (setting 3–4 of 7)
- Zoysia: 1.5–2.5 inches (setting 3–4 of 7)
Stop watering at night
This one alone fixes a lot of dollar spot. Evening watering = dew that lasts all night = fungus paradise.
When to use a fungicide
If you've fed the lawn and the dollar spot keeps spreading after 10–14 days, bring out the fungicide. Same if the patches are merging into larger dead zones.
Products that work on dollar spot:
- Scotts DiseaseEx (azoxystrobin) — easy granular at Home Depot, Lowe's, Canadian Tire. Apply with a hand spreader and water in.
- BioAdvanced Fungus Control for Lawns (propiconazole) — granular or liquid. Wide-spectrum, covers brown patch and rust too.
- Heritage G (azoxystrobin, pro-grade) — Tractor Supply, Site One. Longer residual.
- Propiconazole concentrate (Quali-Pro, Bonide Infuse) — mix-and-spray. Hose-end versions are easiest for homeowners.
Apply on a calm morning. Cover the whole affected area plus a 5-foot buffer of healthy grass. Don't mow for 24 hours after application.
Most fungicides give 14–28 days of protection. Reapply if conditions stay hot, humid, and dewy.
Worth flagging: propiconazole and azoxystrobin work by different modes of action. Rotate between them rather than using the same product back-to-back. This prevents fungus from developing resistance.
Why dollar spot returns year after year
If you got it last summer, expect it again this summer unless you change something. Dollar spot spores survive winter in the thatch and infect the same areas every year when conditions return.
To break the cycle:
- Feed the lawn through summer — don't let it run out of nitrogen
- Dethatch and aerate every 1–2 years
- Switch to early-morning watering
- Sharpen your mower blade in spring
- Mow taller in summer
Do those five and dollar spot drops dramatically.
Frequently asked questions
Can I just leave dollar spot alone?
Small isolated patches will sometimes fade on their own when the weather cools and the lawn grows out of it. But if you see new spots every week, it will spread. Feed the lawn — that alone usually handles it.
Does mowing spread dollar spot?
Mowing through wet patches can spread spores to clean areas. Mow when the lawn is dry, ideally late morning after dew burns off but before mid-day heat. Bag the clippings until the disease stops spreading.
Is dollar spot dangerous to pets or kids?
No. Dollar spot is a plant disease only. The patches and the fungus pose no health risk to people or animals.
How long does dollar spot last?
Active infections last as long as the conditions support them — usually 2–8 weeks during warm humid stretches. Once nights cool below 60°F or daytime humidity drops, the fungus stops spreading and the lawn starts to recover.
What grass is most resistant to dollar spot?
Modern tall fescue varieties (Rebel, Titan, RTF) and newer Kentucky bluegrass cultivars have decent resistance. Old common bluegrass and creeping bentgrass are highly susceptible. If you keep getting hit, consider overseeding with disease-resistant varieties in fall.
How Lawnova catches dollar spot early
Lawnova watches your local humidity and dew-point trends. When the conditions for dollar spot line up, we flag a "fungus watch" task in your plan and prompt you to check for hourglass lesions on the morning rounds. We also remind you to feed the lawn before it gets hungry — the single biggest dollar spot preventer.
Get your free Lawnova plan and stay one step ahead of summer fungus.
Catch the silver-dollar patches early — they spread fast when you ignore them.