Leather Jackets are the larvae of the Crane Fly, commonly known as ‘Daddy Long Legs’. The adult Crane Fly is usually found in the late summer & early autumn; late July to September. An adult female Crane Fly will lay around 300 eggs on the soil surface of the lawn. Around 90% of the eggs are laid within a few metres of the site of the emergence of the adults.
Eggs hatch within 2-3 weeks into the small grey/brown larvae, which are rubbery to the touch. The larvae live in the soil and immediately begin feeding on the roots of the grass. They are well adapted to life in damp, wet conditions; a problem made worse by the ever increasingly mild, damp winters that are now commonplace in Scotland.
The Larvae thrive and feed vigorously on the roots of your lawn during the winter and into early spring. They mature during late May/June by which time they can reach 4cm long. They cease feeding; pupate in the soil and the adult Crane Fly emerges late July/early September.
Damage will vary depending on the infestation (number of larvae per sq.m) from a yellowing of the grass with lacklustre growth, to the total ‘dying back’ of the grass, leaving bare patches on the lawn. In this case, some re-seeding would be necessary. Damage can also occur from an increase in bird activity, scratching at the lawn surface, attracted to the larvae.
Effective treatment would be through the use of insecticide. However, changes in government legislation in May 2015, means many insecticides have been removed from the market and can no longer be used in domestic and amenity turf.