Why does my lawn have brown patches?
A diagnostic order for dead patches — grubs, disease, drought, urine or the mower — based on the shape of the patch and whether the turf lifts.
- Difficulty
- beginner
- Time
- 25 min
- Read
- 3 min
Short answer
Pull at the turf first. If it lifts like a carpet with no roots, it is grubs. If it is firmly rooted, ask whether the patch is round — round means fungal disease, irregular means drought, urine or a mowing fault. That one test settles most of it.
Brown patches all look similar from a standing position and are entirely different problems underneath. The order of the checks matters more than knowing every disease name.
Step by step
- Tug the turf in the patch.If it peels back with almost no roots underneath, chafer grubs or leatherjackets have eaten them. You will usually find white C-shaped grubs or grey leathery larvae in the top 50mm.
- Look for birds and animals digging.Magpies, crows and badgers tearing a lawn up are after grubs. The tearing is a symptom, not the cause.
- Check the shape.Circular or ring-shaped patches with a defined edge point to fungal disease. Irregular shapes point to environmental or mechanical causes.
- Look closely at a circular patch in damp weather.Pink or red needle-like threads at the leaf tips is red thread, which is common, mostly cosmetic and indicates low nitrogen. A greasy grey-white edge in cold wet weather is fusarium.
- Feel the soil under an irregular patch.Rock hard and dry in summer means drought over a compacted or shallow area — often over a buried path, a rubble patch or a heavily walked route.
- Look for a dark green ring.A small scorched patch ringed with lush green is dog urine, and behaves quite differently from everything else here.
- Check for straight edges.Straight lines, stripes or rectangles follow a machine. A mower set too low scalps high spots; spilt or unevenly spread fertiliser scorches in bands.
- Treat according to what you found.Grubs need biological nematodes applied at the right soil temperature. Red thread needs a nitrogen feed. Drought needs aeration and a higher cut. Scalping needs the mower raising.
- Reseed after the cause is fixed.Rake out the dead material, loosen the surface, seed and keep damp. Reseeding before fixing the cause simply feeds the same problem.
Tips
- Lift a corner of the turf before doing anything else. It settles half the diagnosis.
- Red thread looks alarming and is mostly a feeding problem, not a disease to fight.
- Straight-edged damage is always something you did with a machine.
Common mistakes
- Watering brown patches without checking the cause — If the roots have been eaten by grubs, or the patch is fungal, extra water makes it worse. Wet grass favours most lawn diseases.
- Applying a fungicide before identifying the problem — Most brown patches in UK lawns are not fungal, and domestic fungicides do very little to the ones that are. The feeding and mowing regime does more.
If it doesn't work
Turf lifts with no roots
Cause: Chafer grubs or leatherjackets — Fix: Apply the appropriate nematodes when soil is warm and moist, then repair the turf. Keep the lawn well watered while it recovers.
Circular patches with pinkish threads
Cause: Red thread, a low-nitrogen fungal problem — Fix: Apply a nitrogen-containing feed. It grows out. Collect clippings while it is present.
Patches only in hot dry weather, soil hard
Cause: Compaction plus drought — Fix: Aerate, raise the mowing height, top dress and overseed in autumn.
Straight-edged or striped browning
Cause: Scalping or uneven fertiliser — Fix: Raise the mower, level the high spots over time, and apply feed with a spreader rather than by hand.
Questions people ask
How do I tell grub damage from disease?
Pull the turf. Grub damage lifts away because the roots have been eaten; disease patches stay firmly anchored. It takes five seconds and it is the most useful test there is.
Is red thread serious?
No. It disfigures the lawn but rarely kills it, and it usually means the grass is short of nitrogen. A feed clears it over a few weeks.
Will brown patches recover on their own?
Drought patches green up after rain. Disease patches recover once conditions change. Grub damage does not — the roots are gone and the area needs reseeding.