Garden pest control - Leatherjacket (Description and control instructions)

Scientific Name: Tipula paludosa
Other Names: Crane Fly, Daddy-long-legs

The larval stage of the Crane Fly feeds on the roots of grass causing yellow patches; they will also attack potatoes, strawberries, cabbages and lettuce if they are planted in newly cultivated grassland. Pot plants can also be attacked and can be greatly reduced in vigour or even killed - bulbs may never emerge if the young shoots are eaten away. Birds and Badgers find them a good source of food and cause unsightly marks on the lawn as they forage for the grubs.

I have just found some young lettuce and tomato plants shredded by them in the polytunnel, they appeared to be trying to drag the plants into the soil and the culprit was found a few inches below the surface (a bit like the monsters in the film "Tremors").

The female lays about 300 eggs on the soil surface after mating. They hatch in autumn developing until late spring. Pupating in the summer, the adults emerge in autumn to begin the cycle again.

A cultural control to use is covering a well-watered patch of grass overnight with a sheet of black plastic or a tarpaulin, the leatherjackets rise to the surface into the moist space. At dawn they can be swept up or left for the birds. Starlings love them and can be seen in flocks feeding on infested areas. Digging over affected areas and a summer fallow, will allow the birds better access.

This is not an option when they are causing dead patches in the lawn and there is now a biological control which uses a parasitic nematode called Steinernema feltiae. It is applied to moist soil from late August to October when the soil temperature is above 10C / 50°F and the young leatherjackets are active. The nematodes invade the grubs and over a period of 4 to 6 weeks cause them to shrink and die. They are supplied under the trade name Nemasys Leatherjacket Killer and can be ordered by mail or online at any time, but will be delivered at the best time for use in September. (They are also effective against Cockchafer Grubs).

Turn out potted plants to see it leather jackets are present, there will probably be tunnels around the edges.

Provado Lawn Grub Killer which contains Imidacloprid is a recent introduction for the treatment of Leatherjackets and Chafer Grubs.