How To Deal With Leatherjacket in Your Irish Garden
What is Leatherjacket?
Leatherjackets are the larvae of crane flies (daddy-long-legs), and they are among the most damaging lawn pests in Ireland. The larvae are greyish-brown, legless, tough-skinned grubs about 30mm long that live in the soil, feeding on grass roots. Adult crane flies emerge in large numbers in late summer and autumn, laying their eggs in lawns and grassed areas. The larvae hatch in autumn and feed through winter and spring, causing damage that becomes most visible from February to May. Leatherjackets are named for their tough, leathery skin which makes them resistant to many predators. They are particularly common in Ireland's western counties where high rainfall and mild temperatures create ideal conditions.
Damage Caused by Leatherjacket
Leatherjackets eat grass roots, causing yellow and brown patches in lawns that gradually spread as the grubs feed through the root zone. In severe infestations, large areas of lawn can be killed, with dead turf easily peeled away from the soil surface. As with chafer grubs, secondary damage from birds digging up the lawn to feed on leatherjackets can be as destructive as the grubs themselves. Starlings are particularly adept at probing for leatherjackets. Young vegetable plants, strawberries and ornamental seedlings planted in soil with high leatherjacket populations can also be attacked.
How to Prevent Leatherjacket
Maintain a healthy lawn through regular feeding, watering and aeration to help grass withstand root damage. In September and October, when adult crane flies are laying eggs, cover the lawn with fine mesh or fleece overnight to prevent egg-laying if populations are known to be high. Encourage natural predators — starlings, rooks and hedgehogs are all effective leatherjacket predators. Improve soil drainage, as leatherjackets prefer moist conditions.
How to Treat Leatherjacket
Apply nematode biological controls (Steinernema feltiae) to the lawn in September or October when the leatherjacket larvae are young and near the soil surface. Soil temperature should be above 10°C. Water the lawn before and after application and keep moist for two weeks. An effective traditional method is to water the lawn heavily in the evening, then cover affected areas with black plastic sheeting overnight — leatherjackets come to the surface and can be collected in the morning. Birds, especially starlings, provide excellent biological control.
Leatherjacket in Ireland
Leatherjackets are extremely common throughout Ireland and are arguably the most significant lawn pest in the country. The mild, wet Irish climate is ideal for crane fly populations, with western counties including Galway, Mayo, Clare, Kerry and Cork experiencing the highest leatherjacket densities. The combination of high rainfall, mild winters (which allow year-round larval feeding) and extensive grassland creates perfect conditions. Many Irish golf courses, sports grounds and domestic lawns suffer regular leatherjacket damage. Organic control with nematodes has become the standard treatment approach as chemical alternatives have been withdrawn from the market.
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