If you suddenly find that patches of your lawn are dying off mysteriously, there’s a chance that you may have a leatherjacket infestation. But what are they? How do you identify them? And what should you do when they make your lawn their home?
To help answer these questions and more, here’s our guide to how to get rid of leatherjackets in lawn to give you all the information you need about dealing with these awkward and unwelcome pests.
What are leatherjackets?
Leatherjackets are the larvae of craneflies, more commonly known as daddy longlegs. Although there are thought to be around 300 species of craneflies present in the UK, Tipula paludosa is the species most likely to cause problems for your lawn.
Craneflies mostly emerge in the summer and only live for a couple of days, during which time they mate before laying their eggs in the ground.
These eggs then hatch, and the grubs that emerge are what we call leatherjackets. They remain in the ground until the following summer when they metamorphose into craneflies, which leave the ground to mate, lay eggs and continue the cycle.
If you want to learn more about craneflies, check out this short documentary video.
What problems do they cause?
In the larval stage, leatherjackets feed on plant roots, and the roots of your lawn are their meal of choice. For part of the year, they are too small to do much damage, but as they get bigger and their appetites grow, your lawn can suffer significantly and may even die.
As if that weren’t bad enough, leatherjackets constitute a tasty snack for a whole range of other animals, including birds, badgers, foxes and more.
This means that when leatherjackets are on the menu, these animals are capable of digging up your lawn and making a mess of your garden to get at them.
As a result, due to the leatherjackets themselves as well as the predators trying to eat them, if you don’t act, an infestation of these greedy invaders can leave your grass in a sorry state.
What do they look like?
In the early stages, leatherjackets are tiny, perhaps less than 1cm long. However, as the season progresses, they can grow to as long as 3cm or more.
The grubs have elongated grey-brown bodies, and a distinguishing feature is that they have no obvious head or legs.
What are the signs that you have leatherjackets in your lawn?
For most of the year, you probably won’t be aware that you have leatherjackets in your lawn – unless you happen to come across them while digging.
This is because from the time when they emerge from their eggs in late summer until April the following year, they are too small to affect your lawn. They may be busy nibbling away underground, but healthy grass will grow roots back more quickly than the grubs can eat them.
However, moving towards the end of April and into early summer, they begin to increase in both size and voraciousness, and if you have a significant infestation, your grass will begin to show it.
You will start to notice patches of grass turning yellow or dying out, and if you try to pull it up, you will find it comes up easily since most of the roots have been eaten away.
Another tell-tale sign to look for is bird activity in your lawn. If you have unusually large numbers of birds pecking at your lawn, it’s a clear indication that there’s something there of interest to them – and there’s a good chance that something is leatherjackets.
Even more serious, if you find larger animals are turning up to dig through your lawn, this can give you a big clue that you have a serious leatherjacket problem since these animals are being drawn to them as a source of food.
Similarly, molehills can also suggest the presence of leatherjackets because moles are partial to these tasty grubs too.
How to check for leatherjackets
If your lawn is suffering and you suspect leatherjackets are behind it, there are a couple of things you can do to check.
The simplest method is to take a garden fork and dig a few exploratory holes. Choose a spot where your grass has died and turn over a few inches of soil with the fork. Sift through it with your hands and see if you can find any leatherjackets in there.
Here’s a video showing a gardener doing just this.
Alternatively, you can use the polythene sheet method. For this, start by giving the area you suspect to be infested a good soak. This will encourage them to come to the surface.
Next, cover the area with a black polythene sheet and fix it in place with some bricks.
Leave it overnight and come back to check the next day.
When you turn it over, if leatherjackets are present, they will have emerged from the ground and be stuck to the sheet. This will tell you whether they are present and if they are, how serious the infestation is.
What to do if you have an infestation
The first thing to understand is, just because you discover one or two leatherjackets in your lawn or garden, it doesn’t mean you’re infested.
Leatherjackets and craneflies are a common and natural part of British fauna, and it is normal for them to be present. This means if you come across just a couple while digging – or you see a few daddy longlegs flying about in summer – you can probably safely ignore them.
You only need to take action when their numbers begin to cause problems, and when that happens, there are a couple of options, depending on the severity of the invasion. No insecticides legal in the UK are effective against leatherjackets, so here are your options:
1. The plastic sheet technique
If your infestation is not too serious, it can be treated by an extension of the ‘plastic sheet’ method above. Simply use the plastic sheet to bring the leatherjackets to the surface and then remove them one by one and destroy them.
If your infestation is not too serious or is limited to a smaller patch of lawn, this may be all that’s required.
2. Nematodes
Another option is to use nematodes, microscopic worms (Steinernema feltiae) that get inside leatherjackets and infect them with bacteria that kills them.
Nematodes can be bought in the form of a fibrous paste that is then mixed with water and applied to your lawn with a watering can.
This might sound like the perfect solution, but unfortunately, nematodes don’t always help.
They require warm, moist soil, and will only kill leatherjackets while they are still small. This means timing is vital; otherwise, they won’t be effective.
Here’s a quick video about using nematodes to treat grass.
3. Replace your lawn
If your infestation is extremely severe and you have already lost large swathes of grass to the bugs, it could be time to go nuclear and replace your whole lawn.
If you want to take such a drastic step as this, first treat your existing lawn with a weedkiller containing glyphosate.
This will kill not only any weeds in your lawn but also the grass itself – but this is desirable since it will remove the grubs’ food sources, starving them to death.
Leave your dead lawn for a few weeks to make sure no leatherjackets survive and then follow the normal procedures for reseeding your lawn or replacing it with turf.
How to Prevent Leatherjackets in Lawn
As you have probably worked out by now, there is no simple way to deal with a serious infestation of leatherjackets, so the best plan is to prevent them from becoming established in the first place.
Here are some steps to follow that will help keep them at bay:
4. Keep your lawn healthy and well-drained
In general, healthy lawns can defend themselves against all kinds of pests much better than unhealthy or sparse lawns, so the first thing is to always follow standard best practices to keep your grass in great shape.
Scarify your lawn as necessary to remove any build-up of thatch. This will remove any eggs that have been laid, and it will also allow your grass to grow thick and lush, making it more difficult for craneflies to lay their eggs there.
Since leatherjackets in the first stage of life require plenty of water, aerating your lawn and ensuring proper drainage will deprive them of this and will also stop them becoming established.
Also, feeding your lawn in early autumn and again in midwinter will help it regrow any roots lost to leatherjacket activity.
5. Keep your eyes open
If you notice increased cranefly activity in summer, there’s a good chance they will be laying lots of eggs in your lawn. This can serve as a warning, allowing you to start taking the necessary action early.
6. Use nematodes as a preventative measure
One thing you can do if you see lots of craneflies in summer is to apply nematodes pre-emptively. This way, you can set the nematodes on the grubs when they are just emerging, increasing the chance of the nematodes wiping them out.
Keep them at bay – and take action when they try to move in
The best way to deal with leatherjackets is to prevent them from becoming established in the first place. If one or two move in, it’s no big deal – but if you see a real infestation developing, it’s best to take the necessary steps early to help protect your lawn from potential damage.
