Brown patches in the lawn, and how to work out the cause

December 14, 2025

A brown patch turning up in the middle of a lawn that was fine a fortnight ago is one of those things that sends people straight to the fertiliser, and it's worth slowing down for 5 minutes first, because there are a handful of usual causes and they each need something different, so feeding a lawn that's actually being eaten by grubs just gives the grubs a better meal.

Round patches with a green ring

A roughly round dead patch with a ring of darker, lusher grass around the edge is nearly always the dog. Urine is very high in nitrogen, so it burns the middle and feeds the edge. Hosing the spot down well straight after the dog's been there dilutes it, and a dead patch will usually fill back in from the edges or with a bit of patch repair seed.

Patches that stay dry after watering

If you water and the water beads up and runs off a patch instead of soaking in, the soil has gone water repellent, which is very common here in sandy soil after a hot dry spell. Poke your finger or a screwdriver into it and it'll be dry underneath even after rain. A wetting agent fixes that, because it helps water get back into the soil, and once it's soaking in again the grass usually recovers on its own.

Patches that lift like carpet

Lawn grubs and caterpillars feed on the roots and the leaf, and the giveaway is grass that pulls up easily like loose carpet, or birds spending a lot of time pecking at one spot. To check, mix a bit of dishwashing liquid into a bucket of water, pour it over a square metre at the edge of the brown patch and wait a few minutes, and if you've got caterpillars they'll come up to the surface. Only treat if you actually find them, and follow the label on whatever you use.

Thin, worn patches

A patch along a path the kids or the dog run every day, or where the car goes over the edge, is usually compaction, because the soil has been squashed so hard that water and air can't get to the roots. Aerating it and keeping the traffic off for a while does more good than any amount of feeding.

Patches in humid weather

Irregular brown patches that show up in warm, muggy weather, especially in a lawn that gets watered in the evening, can be a fungal problem. Watering early in the morning so the grass dries during the day takes away most of what the fungus needs, and it's worth bringing a sample in so we can have a look before you buy anything for it.

Rings and mushrooms

A dark green ring, sometimes with mushrooms popping up along it after rain, is a fairy ring, which is a fungus living in the soil rather than on the grass. The soil inside the ring often goes water repellent, so aerating it and using a wetting agent helps the grass along, and it tends to be slow to clear completely.

And the mower

Yellow or brown scalped strips on the high spots of a bumpy lawn are often the mower cutting too low, so lifting the cutting height a notch can fix it on its own.

Shop related products

Lawn Grub & Beetle Kill Hose On 2L. For a lawn where you've confirmed grubs or caterpillars.
Brunnings Turbo Patch Repairer For Lawns 800g. For filling in a dead patch once you've fixed the cause.
Brunnings Green Up Lawn Food 5kg. A lawn food for once the problem is sorted and the grass is growing.
Brunnings Tough Lawn Seed 1kg. A couch blend for reseeding bigger bare areas.

Did you know we also stock a lawn aerator and a wetting agent for lawns in the shop, and they aren't on the website, so give us a ring on (08) 8536 4333 to check what's on the shelf.

The rest of the lawn range is in our garden centre, and a photo of the patch on your phone is often enough for us to have a decent guess at what's going on.