Leatherjackets: how to get rid of leatherjackets

How to identify leatherjackets

Found in the soil of lawns, leatherjackets are grey, tubular grubs up to 3cm long, with tough, leathery skin (hence the name 'leatherjacket'). However the first sign of them is not likely to be the grubs themselves but the yellow and brown patches that develop on your lawn as a result of them eating the roots beneath the surface. If leatherjackets are the culprit, when you lift the affected turf you will find leatherjackets in the soil below.

The leatherjacket lifeycle

The leatherjacket lifecycle is annual: after mating in late-summer, female crane flies lay up to 300 eggs directly into the soil or turf. These hatch after a couple of weeks into grubs, which feed on grass and plant roots from autumn through to summer. In a cold winter they tend to hibernate and lawn patches don't appear until summer. However in a mild winter the leatherjackets continue eating and yellow and brown lawn patches can be seen from late winter. After feeding sufficiently, the grubs pupate in the soil and emerge as adult crane flies in late-summer, to mate and start the whole process again. When the adults emerge, the pupal case is often visible, sticking up above the lawn surface.

Why are leatherjackets a problem?

Leatherjackets aren't always a problem in gardens – they are a natural part of the garden ecosystem and many complete their lifecycles without us noticing. However, because some feed on the roots of grasses, they can cause noticeable damage in lawns, especially if present in large numbers. In flower beds or plots, seedlings and small plants can be killed if the stems are damaged, however lawn grass usually recovers.

On top of the damage caused by leatherjackets, crows, magpies, rooks and starlings all feed on them and will look for them by inserting their their beaks into the turf. This leads to unsightly holes in the lawn.

Controlling leatherjackets

Leatherjackets are part of the garden ecosystem and are an important source of food for birds, particularly starlings, so its best to tolerate them if possible. However, if you want to remove them, the easiest thing to do is to soak the lawn and cover it with black plastic (such as old compost bags) or other light-suppressing material. The following morning, when you lift the plastic you should find the grubs on the surface of the lawn. You can then leave these for the birds to find.

Biological control is available in the form of nematodes, which you water onto the turf or soil. The nematodes infect leatherjackets and other soil-dwelling invertebrates with a bacterial disease, which could affect other organisms as well as your target species. Also, nematodes need to be applied when the soil temperature is no lower than 12°C, so are not usually appropriate to use in winter, when the damage often starts to be noticeable.

Frequently asked questions

Once I have got rid of leatherjackets, will they come back?

Yes, it's perfectly possible that female craneflies will lay eggs in your lawn the following year, so you may find you want to control them every year.

Can't I just leave leatherjacket control to nature?

Yes, this is by far the best way to deal with leatherjackets, as many birds, such as starlings, rely on them for a source of food.

Can a lawn recover from leatherjackets?

Yes, in time a lawn will recover from leatherjackets. If a large area is affected you may consider laying new turf, however if the brown and yellow patches are small these should recover quickly without intervention.