Lawn Pests: Leatherjackets and Chafer Grubs

If your lawn has developed mysterious yellow patches, feels spongy underfoot, or you have noticed birds frantically pecking at the grass, there is a good chance you are dealing with lawn grubs. Leatherjackets and chafer grubs are the two most destructive lawn pests in the UK, and they can turn a healthy lawn into a patchwork of dead grass surprisingly quickly.

The real damage often is not from the grubs themselves, though they do plenty of harm. It is the secondary destruction caused by birds, foxes, and badgers tearing up your lawn to feast on the larvae beneath. Understanding which pest you are dealing with and when to act is crucial for saving your lawn.

Leatherjackets: The Crane Fly Larvae

Leatherjackets are the larvae of crane flies (daddy longlegs), those leggy insects that invade your house every autumn. The adult flies themselves are harmless, but their offspring are lawn destroyers. Female crane flies lay eggs in lawns during late summer, and the resulting grubs spend autumn through spring feeding on grass roots just below the surface.

Leatherjackets are grey-brown, legless grubs that look like small, tough tubes. They can grow up to 30mm long and have a distinctive tough, leathery skin (hence the name). You will find them in the top 5cm of soil, often revealed when you lift a section of damaged turf.

The damage they cause typically appears as yellowing patches that spread through autumn and winter. The grass feels loose because the roots have been eaten away, and you can often pull up affected turf like a loose carpet. Starlings, rooks, and magpies love leatherjackets and will probe your lawn relentlessly to find them.

Chafer Grubs: The C-Shaped Destroyers

Chafer grubs are the larvae of various chafer beetles, including the garden chafer and the larger cockchafer (May bug). They are easy to distinguish from leatherjackets by their creamy-white colour, distinctive C-shaped curl, and visible brown head with six legs near the front.

Chafer grubs cause similar damage to leatherjackets, creating bare patches where roots have been destroyed. However, they are particularly notorious for attracting larger animals. Badgers and foxes can smell chafer grubs beneath the surface and will literally tear your lawn apart to reach them, sometimes destroying square metres of turf in a single night.

How to Check for Lawn Grubs

If you suspect grubs, perform a simple test. Cut a 30cm square section of turf in an affected area and peel it back like a carpet. Healthy soil should have no more than a handful of grubs per square foot. If you count more than 25-50 leatherjackets or 5-10 chafer grubs in that section, you have an infestation that needs treatment.

The timing of your inspection matters. Leatherjackets are most active from October through May, while chafer grubs are typically found from autumn through to the following summer. Both are easiest to find when the soil is moist.

How to Treat Lawn Grubs

The most effective treatment for both leatherjackets and chafer grubs is biological control using nematodes. These are microscopic parasitic worms that seek out and kill grub larvae without harming anything else in your garden.

Nematode Treatment Timing

Timing is absolutely critical with nematodes. They only work when the soil temperature is above 12 degrees and when grubs are small and vulnerable. For leatherjackets, apply nematodes between September and October. For chafer grubs, the window is typically August to September. Check soil temperature with a probe before applying.

Application Method

Nematodes come as a powder that you mix with water and apply using a watering can or hose-end sprayer. Water the lawn thoroughly before and after application, as nematodes need moist soil to move through and locate grubs. Apply in the evening or on an overcast day to prevent UV damage to the nematodes.

Keep the soil moist for at least two weeks after treatment. If the lawn dries out, the nematodes will die before reaching their targets. Aerating your lawn before treatment can help nematodes penetrate the soil more effectively.

Repairing Grub Damage

Once you have treated the infestation, you will need to repair the damage. Dead patches will not recover on their own since the grass roots have been destroyed. The approach depends on the extent of damage.

For scattered patches, overseeding with a fast-germinating grass seed will fill the gaps within a few weeks. Rake out any dead material, loosen the soil surface, and apply seed at the recommended rate.

For severe damage covering large areas, you may need a full lawn renovation. This involves scarifying to remove dead material, aerating compacted soil, and overseeding the entire lawn. Autumn is the ideal time for renovation as soil is still warm but conditions are moist.

Preventing Future Infestations

While you cannot completely prevent crane flies and chafer beetles from visiting your garden, you can make your lawn less hospitable to their offspring.

Healthy, well-maintained lawns are more resilient to grub damage because they have deeper, stronger root systems. Regular feeding, proper mowing height, and good aeration all contribute to a lawn that can tolerate some grub activity without dying off. For a complete guide to building a resilient lawn, see our lawn care troubleshooting hub.

Nematodes do not provide lasting protection since they die once grubs are eliminated. Many gardeners apply preventative nematode treatments annually in late summer, especially in areas with known pest pressure. It is far easier to prevent an infestation than to repair the damage afterwards.

If animal damage is your main concern, some gardeners have success with physical barriers like chicken wire pegged over vulnerable areas during peak activity periods. This will not stop the grubs but does prevent foxes and badgers from tearing up the lawn.