Brown Patches In The Lawn

What's happening?

Brown patches have several very different causes and the treatments contradict each other, so identifying which you have matters more than acting fast. The test that separates them takes seconds: try to lift the brown turf. If it peels back with no roots holding it, something has eaten the roots: chafer grubs and leatherjackets both do exactly that, and the secondary sign is birds, badgers or foxes tearing the lawn up to get at them. If the turf is firmly rooted, the cause is above ground: drought over a shallow or stony patch, a dog urinating in the same place, fertiliser or a spillage scorching the grass, or a fungal disease. Patches that follow a straight line usually trace a buried service trench or a strip of thin soil.

What usually causes it?

• Chafer grubs feeding on the roots, leaving turf that lifts freely and attracts birds and mammals digging
• Leatherjackets (crane fly larvae) doing the same damage in the same way
• Drought stress over shallow soil, rubble or a buried obstruction that holds little water
• Dog urine scorching the grass in repeated spots, typically with a darker green ring around a dead centre
• Fertiliser burn from uneven spreading or a spillage, often in sharp-edged patches or stripes
• A fungal disease such as red thread, which discolours the leaf but leaves the roots intact
• Petrol, oil or a cleaning product spilled on the grass, or scalping where the mower has cut into a high spot and taken the sward down to the base

Is it dangerous?

No. It is a lawn health problem. The only cautions are practical: pesticide and biological controls for grub problems have specific approved uses and timings, so read what you are applying and do not treat on the assumption of grubs without confirming them; and a lawn being dug up nightly by badgers is worth identifying properly because badgers and their setts have legal protection.

Can I fix it myself?

Do the lift test on a brown patch and look at what you find. Turf that peels away with no roots means grubs, and turning it back reveals white C-shaped chafer grubs or grey-brown legless leatherjackets in the top few centimetres. Turf that stays rooted points to drought, scorch or disease. Water thoroughly in dry spells rather than lightly; dilute dog urine spots with water immediately; keep fertiliser off the drive and spread it evenly; and raise the mowing height so high spots are not being scalped. Re-seeding a bare patch works once the cause is dealt with, not before.

When should you call a gardener?

Call a gardener if the turf lifts without roots, if animals are digging the lawn up, if the patches are spreading across the lawn, or if you have re-seeded a patch and it has browned again. Grub damage in particular needs identifying to species and treating in a specific window, and re-seeding over an active infestation loses the seed as well. Also call where the patches follow lines or hollows, which usually means the soil beneath needs attention rather than the grass above.

What will the gardener actually do?

• Lift sample turf to identify whether roots have been eaten and, if so, which larva is present
• Separate drought, scorch, urine damage and disease by pattern, rooting and leaf symptoms
• Apply an appropriate control for the identified pest at the correct point in its life cycle
• Improve the root zone where soil depth or compaction is the underlying cause, by aerating and top-dressing
• Repair the damaged areas by lifting dead turf, preparing the soil and over-seeding or patch-turfing
• Adjust the mowing height and set a watering and feeding regime that suits the lawn's soil and aspect

Questions people ask

Sources & References

1. RHS: Chafer grubs in lawns
2. RHS: Red thread
3. RHS: Lawns