Leatherjackets in Your Lawn: How to Spot Them and What to Do

If your lawn has started developing thin, yellow or bare patches and you can’t work out why, the problem might be hiding beneath the surface.

Leatherjackets live in the soil and can damage grass by feeding around the root zone. Because you often won’t see them unless you go looking for them, it can be easy to mistake the symptoms for another lawn problem.

The good news is that there’s a simple way to check whether leatherjackets are present, and if you do find them, there are steps you can take to control them.

What are leatherjackets?

Leatherjackets are the larvae of crane flies, commonly known as daddy longlegs.

Crane flies lay their eggs around grassy areas, and after hatching, the larvae live in the soil beneath your lawn. They’re greyish-brown, legless and have a long, slightly wrinkled body with the tough, leathery appearance that gives them their name.

While the adult crane flies you see flying around your garden are harmless to your lawn, their larvae can cause problems below ground.

What damage can leatherjackets cause?

Leatherjackets feed around the roots and lower parts of grass plants. When there are enough of them present, this can weaken the grass and result in visible damage above ground.

You might notice:

• Areas of grass becoming thin or weak
• Yellowing or discolouration
• Bare or dying patches
• Grass that seems to be struggling despite otherwise appropriate lawn care

The difficulty is that these symptoms aren't unique to leatherjacket damage. Poor growing conditions, drought, disease and other lawn problems can produce similar symptoms, so it's worth checking before deciding on a treatment.

How to check your lawn for leatherjackets

Because leatherjackets spend most of their time beneath the surface, you might not spot them simply by looking at your lawn.

Fortunately, you can carry out a straightforward overnight test.

1. Soak a small area of your lawn

Choose an area where you've noticed damage and thoroughly water the ground in the evening.

You want the soil to be properly moist rather than just wetting the tips of the grass.

2. Cover the area

Place a black plastic sheet over the wet section of lawn and leave it there overnight.

Make sure the sheet is sitting against the grass and secure it if necessary so it doesn't blow away.

3. Check underneath in the morning

The following morning, carefully lift the sheet and inspect the surface of the lawn.

If leatherjackets are present, the moist, covered conditions can encourage some of them towards the surface, making them much easier to spot.

Look for greyish-brown, legless larvae with long, slightly wrinkled bodies.

What should you do if you find leatherjackets?

If your test confirms that leatherjackets are present, one option is to treat the affected lawn with leatherjacket-specific nematodes.

Nematodes are microscopic organisms that are applied to the lawn in water and target leatherjacket larvae within the soil.

Timing is particularly important when using them.

Treating leatherjackets in autumn

Leatherjacket nematodes can be applied at the normal recommended dose through October, providing the conditions are suitable for the particular product you're using.

Always follow the instructions supplied with your chosen nematode treatment, including guidance around soil temperature, moisture and application.

What about leatherjackets in spring?

Leatherjackets become larger as they develop, which can make them more difficult to control later in their lifecycle.

If you're treating them in spring, a double dose of nematodes may be required.

Again, check the instructions for the specific nematode product you're using before application.

Can your lawn recover from leatherjacket damage?

Finding leatherjackets doesn't necessarily mean your lawn is beyond saving.

How quickly it recovers will depend on the extent of the damage, the time of year and the overall condition of the grass.

Once the pest problem has been addressed, giving the lawn the right conditions to recover will help. Depending on the amount of damage, this could include appropriate feeding and general lawn maintenance or overseeding areas where grass coverage has been lost.

For more substantial damage, a lawn renovation may be needed to restore coverage.

Don't ignore unexplained lawn damage

When a lawn starts thinning or developing bare patches, it's tempting to immediately reach for grass seed or fertiliser.

But if there's an underlying problem, it's important to identify that first.

If your lawn isn't responding as you'd expect and you can't see an obvious explanation above ground, have a look at what's happening underneath it. A simple overnight test could reveal that leatherjackets have been quietly causing the problem all along.

Healthy lawns start with understanding what your grass needs, both above and below the surface.