Leatherjackets in lawns & turf
Along with earthworms, leatherjackets in lawns are the most damaging of lawn and turf insects or grubs. However they are less common than worms. These grubs are about 25mm long, grey/brown in colour and legless. Leatherjackets are the larval stage of the crane fly or daddy-longlegs as it is more commonly known.
During the late summer the crane fly lay their eggs in the lawn, these eggs then hatch into larvae after about 2 weeks.
They continue to remain in the soil for about 9 months where they feed on the turf and its roots. The most visible damage can be seen in the spring with yellow patches where they have been feeding. It is not only damage from the leatherjackets which causes a problem.
Birds such as starlings feed on the insects and cause damage by pulling the turf up with their beaks. However birds pecking at the turf in the spring time can be a good early warning sign that there are leatherjackets present in the soil. This gives you time to control them before too much damage is caused.
Another method to see if you have these grubs is to lay a tarpaulin sheet on your lawn overnight. Check it in the morning and if there are over 20 leatherjackets per square meter it would be considered a problem and control will be necessary.
Prevention & control of leatherjackets
In the case of leatherjackets prevention is better than cure. If you notice lot's of crane flies on you lawn in the late summer this is a warning you could have a leatherjacket problem the following season.
Leatherjackets favour very wet soils, therefore winters that are very wet help leatherjacket populations. However leatherjackets are very susceptible to drought during the early stages of their life.
If you can recognise the early warning signs autumn is the optimum time to apply and insecticide containing HCH. However if you don't act in the autumn a product based on leatherjacket killing nematodes can be used later.