Leatherjackets can be a common problem in lawns, eating roots and causing patches.
But what exactly are leatherjackets? Are they really a problem? And what should you do about them?
In this article, we’ll take a closer look at these common larvae, how you can work out if you have leatherjackets causing damage in your lawn, flower beds or vegetable patches. And what to do about it if you do.
What are Leatherjackets?
Leatherjackets are the larvae of crane flies, also known as daddy longlegs (Tipula ssp.). There are a range of different species of crane flies present in UK gardens. The larvae are grey-brown in colour, with no obvious head and no legs.
Depending on the species they can be up to 3cm long. They take their name from the fact that these larvae have a tough leathery skin.
The long dangling legs of the adults make them easily recognisable, and they are a familiar sight across the British Isles. Female adult crane flies lay up to 300 eggs in the lawn or on the soil surface some time in the late summer. After a couple of weeks, a proportion of these will hatch into the leatherjacket larvae. If the weather is dry at this time, fewer will tend to hatch successfully.
If the weather over the winter is cold, the leatherjackets will overwinter as small larvae and will not grow to feed on plants or potentially cause problems until the following mid-summer. However, if the winter is mild, young larvae will continue to feed and can begin to cause problems by the time winter is through.
Once the leatherjackets are fully grown, they pupate below the soil surface. The adult flies then emerge from their pupal cases and the life cycle continues.
Are They a Problem in the Garden?
It is important to understand that only a few species of crane fly larvae actually pose a problem in your garden. These few species can be problematic because they eat the roots of lawn grasses, leaving yellow or brown patches and causing the grasses to die back in certain infested areas.
Leatherjackets can also occasionally become an issue in vegetable plots of flower beds, especially in new beds which have recently been created over an area of lawn. The larvae may nibble off seedlings at ground level, causing them to collapse.
How To Identify a Leatherjacket Problem
It is important not to rush to judgement if you see adult crane flies in your garden. Because these may not be of the species which pose a threat to your lawn or seedlings.
If you do see patches of dead or dying grass in your lawn, or patches where birds have made small round holes in the turf, then leatherjackets may be the issue. But it is important to investigate a little to make sure that a different problem is not to blame.
Dry and dying patches of lawn can have a range of causes. To make sure that it is leatherjackets and not a disease or other pest issue, you should lift a patch of the turf that is affected. If leatherjackets are present, you should see that the root system of the affected grass is damaged or practically non-existent, and should find the culprits themselves fairly easily in the upper layers of the soil.
You can also see whether leatherjackets are the problem by watering and then covering the affected area with a layer of black plastic. Leave this is place overnight. The next morning, if leatherjackets are present, lift the cover and you should see a large number of these grubs on the surface.
Where you see holes in the soil where birds have dug in their beaks, this could be a tell-tale sign that larvae are present. Corvids and starlings will look for leatherjackets in this way. However, they could also be looking for chafer grubs.
Foxes and badgers may also dig up chafer grubs, so if there is greater disturbance then chafer grubs may be more likely to be the issue.
In a new flower or vegetable bed, if seedlings or small plants have their stems damaged at soil level and collapse, there can be a number of culprits. Again, looking around in the upper levels of the soil for the leatherjackets themselves will help you identify whether or not these pests are to blame.
Why Leatherjackets Are Sometimes Beneficial in a Garden Ecosystem
Leatherjackets can be a pest for those who like a neat and tidy lawn, and can occasionally be an issue in other parts of the garden. But as mentioned above, it is important to remember that only a small number of crane fly species have larvae which will actually do any damage. And even if you do have an infestation of a damaging type, it will need to be rather a large infestation to pose a serious threat to your lawn grasses or other plants.
It is important to remember that like all other garden creatures, crane flies and their larvae are part of the garden ecosystem. The best way to deal with any pest species is not to eradicate them or get rid of them entirely. Rather, the best strategy is to manage their numbers, and create a balanced ecosystem with plenty of predators to keep their numbers down.
So if you have a lot of crane flies and leatherjackets, look to attract plenty of the birds and other species which eat them to your garden. They can be valuable prey for a range of different animals.
Those many species of crane fly which do not cause damage feed not on roots of plants but on decaying vegetation, fungi etc.. They therefore play an important role in recycling nutrients in the soil and can be beneficial within the garden ecosystem.
How To Deal With a Serious Infestation
If you do have a serious infestation of damaging leatherjackets in your garden, then it is of course important to manage the problem organically. First of all, try to manage the problem by manually removing the larvae, and by taking steps to increase the numbers of natural crane fly predators present in your garden. If all else fails, however, there is a biological control to consider.
It is possible to purchase certain pathogenic nematodes – Steinernema feltiae or Steinernema carpocapsae, which can be watered into the lawn, or soil. These nematodes are microscopic organisms which enter the bodies of the leatherjackets and give them a bacterial disease.
These can be used in moist soil, which has a temperature of at least 12 degrees C. When the conditions are right, these should be watered into the area of the infestation and the surrounding area. However, it is crucial not to try this when the soil is too cold.
If the leatherjacket population is out of control and a lot of damage is being caused, these nematodes can be the most effective solution.