What are leatherjackets? Leatherjackets are the larvae of the crane fly and have a thick, long, brown body. A leatherjacket looks a little like a short worm with a hard skin.
What damage do leatherjackets cause? Leatherjackets are active at night, when they go in search of food. The damage that they cause to lawns can be recognized by the brown, bare patches in the grass. There is also a risk of secondary damage from the presence of leatherjackets. Animals such as jackdaws, crows, blackbirds, starlings, and moles like to hunt for leatherjackets, and while they're searching, they dig up the ground, leaving considerable damage behind on the lawn.
The lifecycle of leatherjackets The leatherjackets of the crane fly cause the most damage. The crane fly has a lifecycle of around a year, and adult crane flies only live for a few weeks. The adults take flight from August to October, and then lay new eggs. A larva (leatherjacket) will emerge from the egg after around two weeks, and will then continue to grow for around a year until it pupates to become an adult crane fly. The marsh crane fly is also prevalent and has a longer lifecycle of two years. These crane flies take flight between April and June and August and October. The adults only live for a few weeks, and larvae emerge from the eggs after around two weeks.
Managing leatherjackets with nematodes Leatherjackets are best treated when they are still small, so in the first few months after they have hatched from their eggs. The following is a good rule of thumb: nematodes are most effective if used one to two months after the crane fly has begun to fly. If you're unsure when the crane flies were first seen, the nematodes are best saved for use at the end of October. Nematodes can also be used effectively against the marsh crane fly in July.
What sort of nematode should I opt for? Steinernema carpocapsae is the most effective against leatherjackets. If the soil temperature is below 12°C, it is better to use Steinernema feltiae. The soil temperate is an average of daytime and night-time temperatures.
