Brown patches in your lawn: 9 causes and how to tell them apart

Brown patches almost always tell you what caused them if you look at the shape. Neat circles with a darker outer ring are usually fungal disease. Patches that spread fast and lift like loose carpet are grubs. Isolated spots with a bright green halo are dog urine. A general fade across the whole lawn is more likely drought, heat stress or a mowing problem. Working out which of the nine common causes below you're dealing with is the difference between a fix that works and money spent treating the wrong thing.

None of this is guesswork if you know what to look for. Below is a quick-diagnosis table, then each of the nine causes in more detail — what it looks like on an Australian lawn, why it happens, and how to treat it.

Quick diagnosis: match the pattern to the cause

What you see	Likely cause	Quick test
Whole lawn fading evenly; footprints and mower tracks stay visible	Drought / heat stress	Push a screwdriver into the soil — hard to push in means it's dry
Dry patches in the same spot every time, often near edges or under eaves	Sprinkler gaps	Run the system and watch where the water actually lands
Circular patches with a darker, water-soaked-looking ring at dawn	Fungal disease	Check if you've been watering in the evening or over-fertilising
Patches spread over days; turf lifts like a loose rug when tugged	Curl grubs	Peel back a square of turf and check the soil for C-shaped grubs
Ragged, chewed blades; browning appears almost overnight	Armyworm / caterpillars	Soap-and-water flush brings caterpillars to the surface in ~10 minutes
Small, isolated round spots with a dead centre and extra-green ring	Dog urine	Compare the pattern to where the dog actually toilets
Patches appear right after mowing, following the mower's path	Scalping	Check the mower deck height against your grass type
Thin, patchy growth in high-traffic areas; water pools instead of soaking in	Compaction / thatch	Push a garden fork in — resistance close to the surface means compacted soil
Streaky or blotchy patches in stripes, right after fertilising or spraying	Fertiliser / chemical burn	Check the pattern against your spreader or sprayer's overlap

The 9 causes in detail

1. Drought and heat stress

Through a dry Melbourne summer, most lawns fade from green to a dusty grey-green and then to straw-brown as the grass shuts down to conserve moisture rather than dying outright. The giveaway is that it's even across the whole lawn (or whole sun-exposed sections), footprints and mower tracks stay pressed into the grass for hours, and the soil underneath is genuinely dry. Deep, infrequent watering — enough to wet the root zone, not a daily sprinkle — recovers most drought-stressed lawns within a couple of weeks. Our Victorian lawn care calendar has watering guidance by month if you're not sure how much your lawn needs through the warmer part of the year.

2. Uneven watering and sprinkler gaps

When dry patches show up in exactly the same spot every time, in a shape that doesn't match sun or shade, the cause is usually the irrigation itself rather than the weather — a sprinkler head that's blocked, angled wrong, or just doesn't reach that corner. Run the system during the day and physically watch where the water lands, or set out a few empty cans across the lawn to see which ones fill unevenly.

3. Fungal disease

Brown patch, dollar spot and winter fusarium are the fungal diseases most commonly seen in Australian lawns. They show up as roughly circular brown or straw-coloured patches, sometimes with a darker "smoke ring" edge visible in early-morning dew, and they spread fastest in warm, humid weather — made worse by evening watering (which leaves the lawn damp overnight), thick thatch, poor airflow, and over-fertilising with nitrogen. The first fix is cultural: water in the morning only, don't overfeed, and keep mowing regularly at the right height rather than letting the lawn get away and cutting it back hard. If the disease keeps spreading despite that, a fungicide labelled for lawn disease — products containing mancozeb are a common home-garden option, with tebuconazole-based products used for more persistent cases — can help, but always follow the label rate and withholding period.

4. Curl grubs

Curl grubs are the C-shaped larvae of scarab beetles such as African black beetle and cockchafers, and they feed on grass roots below the surface. Because the roots are being eaten rather than the leaf, damaged turf lifts away like a loose rug when you tug at it, and you may notice birds — magpies especially — pecking or digging at the lawn to get at the grubs themselves. To confirm, cut a small square of turf, peel it back, and check the soil underneath. Products containing chlorantraniliprole give longer residual protection against curl grubs than older contact insecticides, but they need to be watered in afterwards so the active ingredient reaches the root zone where the grubs are feeding — check the label for the exact rate.

5. Armyworm and lawn caterpillars

Armyworm and other lawn caterpillars feed on the leaf rather than the root, so damage looks different to grubs: ragged, chewed, almost see-through blades that brown off fast, sometimes within a day or two, while the turf itself stays firmly rooted. We've covered this one in full in our armyworm identification and treatment guide, including the soap-flush test to confirm it and when it's active in Victoria.

6. Dog urine

Dog urine is highly concentrated in nitrogen and salts, and a dose that strong right at the point of contact can burn out the grass crown, leaving a dead brown centre — often ringed by a patch of extra-green grass where the diluted nitrogen at the edges acted like a mild fertiliser. The pattern is the tell: it's isolated to wherever the dog actually toilets, not weather-driven, and it doesn't spread. Hosing the spot down soon after with plain water to dilute the nitrogen is the most reliable fix. You'll see gypsum recommended online as a cure; the evidence for it is mixed at best, so don't rely on it instead of dilution. Dead centres usually need reseeding or a small turf patch rather than just time.

7. Scalping

Scalping is what happens when the mower cuts below the grass's growing point — usually because the lawn was left too long between mows and got cut back hard to "catch up," or because the ground is uneven and the deck dips into high spots. Damage tends to follow the mower's path exactly, which is the giveaway versus disease or grubs. See our mowing height guide for the right deck setting by grass type, and our guide to how often to mow to avoid letting growth get away between visits in the first place. Top-dressing to level out dips helps stop it recurring on uneven lawns.

8. Compacted soil and thatch buildup

Heavy foot traffic, clay soil (common across parts of the Mornington Peninsula and Melbourne's south-east) and a thick thatch layer between the soil and the green leaf can all stop water, air and nutrients reaching the roots. The result is thin, patchy growth that's often worst along paths, gateways and anywhere kids or pets regularly walk, and water tends to pool on the surface instead of soaking in. Core aeration in spring or autumn relieves compaction, and dethatching or scalping back a thick thatch layer (more than about 1–2 cm) lets the lawn breathe again.

9. Fertiliser or chemical burn

Streaky or blotchy brown patches that turn up in stripes shortly after fertilising or spraying usually mean overlap — passing the spreader or sprayer over the same strip twice concentrates the product enough to scorch the grass, especially with a fast-release, high-nitrogen fertiliser applied ahead of hot weather. Herbicide applied at too strong a rate, or drifting onto the lawn from a garden bed, can do the same. Water the area heavily to dilute and flush what's there, avoid fertilising right before a hot spell, and calibrate the spreader (or walk in a proper grid pattern) so passes don't overlap.

Will it fix itself, or do you need to act?

Drought stress and scalping usually recover on their own once the underlying habit is corrected — proper watering, the right mowing height — and just need a bit of time. Sprinkler gaps and compaction are similar: fix the root cause and the lawn fills back in. Fungal disease, curl grubs, armyworm and fertiliser burn are different — left alone, all four tend to keep spreading rather than settle down, so they're worth treating rather than waiting out. Dog urine spots won't spread, but the dead centre generally won't regrow without dilution and, often, reseeding.

Helping the lawn recover once the cause is fixed

Whatever caused it, recovering turf wants the same basics: consistent watering (not waterlogged, not dry), a light feed once the immediate stress has passed rather than during it, and mowing a little higher than usual while it regrows so there's more leaf area to rebuild the plant. If you're unsure what grass you actually have — which affects how it recovers and how it should be mowed — our buffalo vs kikuyu vs couch comparison will help you identify it. For anything beyond a light DIY fix, our weeding and lawn treatment service covers pest and disease issues like these as part of an ongoing visit.

Frequently asked questions

What does it mean when my lawn has circular brown patches?

Neat, roughly circular patches — especially with a darker ring visible at dawn — usually point to a fungal disease such as brown patch or dollar spot, made worse by warm humid weather, evening watering or over-fertilising.

How do I tell grub damage from drought?

Tug at the brown grass. Drought-stressed turf is dry but still firmly rooted, while grub-damaged turf lifts away like a loose rug because the roots have been eaten. If it lifts easily, peel back a section and check the soil for curl grubs.

Will grass grow back from dog urine spots?

Not reliably on its own — the concentrated nitrogen can kill the crown at the centre of the spot. Dilute with a heavy hose-down soon after the event, and reseed or turf-patch established dead spots rather than waiting for them to regrow.

How long do brown patches take to recover?

Drought and scalping usually green up within a mow or two once corrected. Fungal, grub and armyworm damage takes longer — often several weeks after treatment — since the lawn has to regrow from the roots or crown up, and severe cases may need reseeding or turf.

Should I water brown patches more or less?

It depends on the cause. Dry patches from drought or sprinkler gaps need deep, infrequent watering. Fungal disease needs the opposite — cut back evening watering, since damp turf overnight is what lets it spread.