Leatherjacket grubs can destroy your lawn!

Leatherjackets are one of the most devastating lawn pests found in the UK, literally eating their way through an entire lawn. A severe leatherjacket attack will mean that your lawn has to be entirely replaced … which could cost thousands! Read on to learn how to spot them and how to deal with these potentially troublesome pests if you spot them in your lawn.

What are leatherjackets?

A crane fly (Tipula oleracea) or “Daddy long-legs” CC image by Keith Laverack on Flickr

Leatherjacket grubs are the larval stage of a species of crane fly called tipula oleracea, which is commonly known as the daddy-long-legs.

These curious, clumsy insects are often seen flying around our gardens in late summer and early autumn, bumbling along the ground, getting trapped behind glass windows and flying into our faces when we least expect it!

Unfortunately for them, their lives are very short as adults, with their only aim being to find a mate and lay their eggs for the next generation. They don’t even have any mouth-parts to eat food, so pose no threat to veg or plants. As soon as their energy has been expended, often in less than a day, they expire.

If they are lucky enough to find a mate, the females will fly low to the ground and lay her eggs in the soil (or your lawn), starting the crane fly cycle again.

Just a few weeks later the eggs will hatch into the infamous leatherjacket grub, which will quickly begin to feast on the roots of the plants found around them. They then reduce their activity in the winter due to the cold, but start up again in the spring, voraciously eating their way through the roots in the soil, killing any smaller plants, such as the humble grass plant.

How can you spot leatherjacket grubs in your lawn?

A selection of leatherjacket grubs

Finding out if you have a leatherjacket infection in your lawn is quite simple and you only need a small pocket knife and good knees!

Firstly, have a general look at the lawn and see if you see any patches of obviously dead grass that seem rather out of place and randomly distributed. Then, get down on the ground and have a closer look. First thing to do is to grab a handful of grass and try to pull it up. Healthy grass will not budge, being held in place by the roots. Grass subjected to a grub attack will come away easily, almost like a carpet. With no roots to hold the grass to the ground, the lawn will die suddenly.

Next step is to dig into the lawn and have a look to try to identify a grub. This is important as the remedy will be different to the type of grub found. In the UK you are only likely to encounter leatherjackets, chafer grubs or wireworms. In summary; wireworms are thin and orange, chafer grubs are white, usually curled up in a ‘C’ shape with a black head and leatherjackets are darker coloured, straight and can be over 2cm long.
I found a selection of leatherjackets in a lawn last year and made this short video of one of them wriggling around:

What damage can leatherjackets do to your lawn?

The damage a leatherjacket infestation can do to a lawn can be devastating

In large numbers, leatherjackets can be a very destructive lawn pest, completely destroying a lawn to such a degree that it the grass can be rolled off like a carpet! Such a severe attack is unusual, but even lighter damage can dramatically affect the look of your lawn and can lead to expensive repairs.

The best way to deal with any possible infection is to make sure that it doesn’t get out of hand. Just one or two leatherjackets in a lawn will barely be noticed, but it’s when the they appear in large numbers that you should be concerned and preventative action should be taken as soon as possible.

How can you control leatherjackets?

The only way to control a leatherjacket infection effectively is to control the grub numbers in the soil. There are a number of different methods to control them and, like most garden pests, the best control is to use several methods rather than just relying on one.

• Get help from the birds! – Our feathered friends in the garden love a nice fat juicy grub for dinner, and leatherjackets are just the ticket. Unfortunately the grubs prefer to hide underground, and the birds will happily tear up your lawn to get to them. However, you can encourage them to the surface for the birds to pick off. Simply wait until a wet day (when the grubs move through the soil more easily) then lay some black plastic over the lawn overnight. When you remove it the next day the grubs will be on the surface and will be a nice breakfast for the birds.
• Nemetodes! – This is a relatively new organic treatment which utilises the effect of parasitic nematode worm called Steinernema feltiae for the treatment of leatherjackets. These have to be applied carefully, at the right time and in the correct conditions, but they are a great natural remedy to these lawn pests.
• Insecticide treatment – Unfortunately, effective leatherjacket insecticide treatments are expensive and difficult to find for the home-owner. However, I am licensed to apply a suitable chemical which is proven to be very effective at treating these difficult grubs, and I would be happy to discuss a Lawnscience leatherjacket lawn treatment for your lawn.

Some sources also recommend rolling your lawn to compact the soil, preventing leatherjackets from moving through it and feeding, however I strongly DO NOT recommend this for a domestic lawn, as the resulting damage caused by compacting the soil will be just as bad as a leatherjacket attack! Rolling a lawn is never recommended.

For more information and advice about your lawn, or to book a free lawn survey, please don’t hesitate to get in touch.

Kris Lord
Lawnscience (South Manchester) Ltd