Leatherjackets

When it strikes

When and where to look

Scout the planting while temperatures hold between 5°C and 22°C, with humidity above 80%, after rain or heavy dew, while the leaves are still wet. Risk builds after roughly 12 unbroken hours of those conditions, so the morning after such a night is the moment to look.

The signs that lead here

• Patches and rings in the lawn

Full problem lists for these crops

• 🌱 Lawn

About

Leatherjackets are the larvae of crane flies (daddy-long-legs), and they eat grass roots through autumn, winter and spring. Damage is worst after a wet late summer, because the adults lay far more eggs into consistently damp turf.

Symptoms

Yellowing, thinning patches of lawn that peel back like a carpet because the roots are gone. Birds — starlings, crows, magpies — tear the turf up in numbers, which is often the first thing noticed. Grey-brown, legless, tough-skinned grubs sit in the top 5 cm of soil.

Organic Treatment

Water in parasitic nematodes (Steinernema feltiae) in early autumn while the larvae are small and soil is above 12°C. Alternatively, water the lawn heavily in the evening, cover with black plastic overnight, and collect the grubs that come to the surface at dawn.

Chemical Treatment

No lawn insecticide is available to gardeners for leatherjackets in most of Europe. Nematodes are the accepted replacement and work well if the timing is right.

Prevention

Improve lawn drainage and avoid waterlogging in late summer, when the adults choose where to lay. Scarify to reduce thatch, keep the sward dense and well fed so it outgrows moderate root loss, and overseed damaged patches promptly.