What’s Eating Your Lawn? Leatherjackets and Chafer Grubs Explained
Bald patches, loose turf and birds repeatedly pecking at your lawn can all indicate a problem beneath the surface.
Two common culprits in UK gardens are leatherjackets and chafer grubs. Both feed around grass roots and can cause visible lawn damage, but they are different larvae with different lifecycles. Identifying which grub is present is important because the correct treatment and application timing are not the same.
Signs that lawn grubs may be present
Leatherjackets and chafer grubs can weaken the grass by feeding below ground. The resulting damage may include:
- Yellow or brown patches
- Thin or dying grass
- Areas of loose turf
- Grass that lifts away easily because the roots have been damaged
- Birds repeatedly pecking at the lawn
- Foxes, badgers or other animals digging or pulling up the turf
Some of the most obvious lawn damage may be caused by wildlife searching for the grubs rather than by the grubs alone.
Before applying a treatment, check what is living beneath your lawn.
How to find lawn grubs
Choose an area close to a damaged or thinning patch. Water the ground, then cover it overnight with black plastic sheeting or another dark, impermeable cover. The damp, sheltered conditions may encourage grubs to move closer to the surface, where they can be collected and identified.
If this does not reveal anything, carefully lift a small section of turf or dig into the soil at the edge of a bald patch. Check areas where birds have been feeding or animals have disturbed the ground.
Replace the turf and water it afterwards to help minimise further damage.
How to identify leatherjackets
Leatherjackets are the larvae of crane flies, commonly known as daddy longlegs.
They are usually:
- Greyish-brown
- Long and straight
- Legless
- Tough-skinned
- Similar in shape to a small cigar
Leatherjackets feed around the roots and base of grass plants. They may also be found in borders, pots and other cultivated soil where they can damage plant roots.
Crane flies lay their eggs in grass during late summer and early autumn. The leatherjackets hatch beneath the lawn and begin feeding while they are still small. They overwinter in the soil before feeding more actively as temperatures rise.
Damage often becomes particularly noticeable in March and April, when the larvae are larger and birds or animals begin digging for them. By late spring, they stop feeding and enter their pupal stage before emerging as adult crane flies later in the year.
The most effective time to use Leatherjacket Nematodes is generally from late August to October, while the larvae are young and close to the surface. Apply when the soil temperature is above 10°C.
A useful natural timing guide is to apply the treatment approximately two weeks after you notice adult crane flies appearing over the lawn.
How to identify chafer grubs
Chafer grubs are the larvae of several species of chafer beetle. Adult chafers are sometimes called May bugs.
The grubs are usually:
- Creamy white
- Curled into a distinctive C shape
- Equipped with three pairs of legs close to the head
- Marked with a brown or orange-brown head
Chafer grubs feed on grass roots below the lawn. Heavy infestations can weaken or kill areas of turf, but damage is often made worse when birds, foxes or badgers pull at the lawn to reach the grubs.
Adult chafer beetles emerge during late spring and summer. After mating, females lay eggs in the soil. The young grubs hatch and begin feeding on roots while the ground is still warm.
As the weather becomes colder, they move deeper into the soil. They return nearer the surface as conditions improve, before eventually entering the pupal stage and developing into adult beetles.
Late summer is the best time to apply Nematodes for Chafer Bug, when the newly hatched grubs are small and particularly vulnerable. The soil must be above 12°C for this treatment to work.
A spring treatment may sometimes be considered after a warm spring if active grubs are found before they pupate. However, autumn treatment is generally more effective because the grubs are younger.
Leatherjackets or chafer grubs: the quick difference
If the grub is grey-brown, straight and has no legs, it is likely to be a leatherjacket.
If it is creamy white, curled into a C shape and has three pairs of legs near its brown head, it is likely to be a chafer grub.
Correct identification matters because the nematodes used to treat the two pests are different products.
Why treatment timing matters
Beneficial nematodes are microscopic organisms that are watered into the lawn. They move through moist soil and seek out their target pest.
Young grubs living near the surface are much easier to reach than older larvae or pupae. Once the pest has developed a harder pupal casing, nematodes cannot treat it effectively.
This is why it is better to plan treatment around the pest’s lifecycle instead of waiting until the lawn damage is at its worst.
By the time severe damage becomes visible in spring, the larvae may already be large, tougher and approaching the pupal stage.
How to apply lawn nematodes successfully
Always follow the directions supplied with your chosen nematode treatment. The two products have different minimum soil temperatures, so check the conditions before applying.
For both treatments:
- Mow the lawn before application.
- Make sure the soil is moist.
- Apply in the evening, during dull weather or while it is raining.
- Avoid bright sunlight and very dry conditions.
- Use the product before its stated expiry date.
- Store the unopened pack in the refrigerator if you cannot use it immediately.
- Never freeze nematodes.
- Use the complete pack once it has been mixed.
- Water the lawn after application.
- Keep the treated soil moist for at least two weeks.
Nematodes are fresh, perishable biological controls and should be purchased when you are ready to use them rather than stored for long periods.
Treat the cause, then help the lawn recover
Once the grubs have been treated, give the grass time to recover. Lightly rake away dead material, repair badly damaged patches and keep newly sown or repaired areas watered.
Avoid applying seed to badly disturbed ground until you have checked that the main grub activity has reduced. Where birds or animals have lifted the turf, gently press it back into place and water it well.
A healthy lawn with stronger roots is better able to recover from occasional pest damage, but even well-maintained grass can be affected when grub numbers become unusually high.
Act in late summer and autumn
Spring is often when gardeners first notice the damage, but late summer and autumn are usually the most important times to take action.
Young leatherjackets and chafer grubs are nearer the soil surface, the ground is still warm and autumn moisture helps nematodes move through the soil.
Identify the grub first, check the soil temperature and choose the appropriate treatment:
