The leatherjacket larvae feed on the roots. They are the larvae of crane fly (Tipula spp.). Attacks are more likely to occur after a grass rotation and if there are damp conditions in late summer and early autumn. Dry weather reduces the pest risk because eggs and young leatherjackets are vulnerable to desiccation. The pest can interfere with crop establishment and reduce yield by up to 80% in places. Cereal crops are susceptible to damage as seedlings but can withstand attack better once they have tillered.
Ploughing in July and early August (before the main pest egg laying period) can help to control it.
Large numbers of adult crane flies in July and August and rooks, crows and starlings feeding on grubs indicate possible leatherjacket problems. Monitoring can be done by driving plastic pipes into the ground and filling them to near the brim with brine so that leatherjackets float to the surface. Thresholds for economic damage are 50 per m2, or 5 in 12 pipes or 5 per m of row.
There is currently no effective chemical control available for leatherjackets.
The parasitic nematode Steinernema feltiae (available as 'Nemasys') can be used as an alternative and can be watered onto soil. These parasites infect the grubs with bacteria to kill them. Treat between August and October.