October 1st, 2018 by Chris Chapman

The transition between summer and autumn can be a hard one for your lawn to make. After the long, hot, dry spells throughout summer, your lawn now has to deal with rapidly cooling temperatures and large amounts of rainfall. This can really weaken your lawn, putting it at real risk from a host of bothersome lawn pests and lawn diseases (to find out more about the UK’s most common lawn diseases, click the link). If your lawn starts to look sparse, it could be suffering from an infestation of leatherjackets, one of the UK’s most common lawn pest. But what exactly are leatherjackets and how can you stop them? Read on for all the information you need.

What are Leatherjackets?

Leatherjackets are actually the larvae of daddy long legs, also known as crane flies. Adult daddy long legs are completely harmless and won’t damage your lawn, but their larvae – the leatherjackets – are a completely different story. Daddy long legs actually spend the majority of their life as leatherjackets hatch underground at the end of summer (around September-time) before feeding on grass roots and growing until they’re ready to transform into adults in June. Once they emerge as adult daddy long legs, they only actually survive for around two weeks! What this means is that leatherjackets can survive under your lawn for around ten months feeding on your grass roots. If the drastic weather changes between summer and autumn have weakened your lawn, a severe leatherjacket infestation can finish it off, leaving your lawn looking bare.

How to Identify Leatherjackets

Source: Rasbak [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], from Wikimedia CommonsLeatherjackets are plump, brown grubs which look like they’re covered in leathery skin (hence the name). They aren’t pleasant to look at but they’re very appetising for local wildlife, so the easiest way to diagnose a leatherjacket infestation is to keep an eye on the wildlife on your lawn! Birds, hedgehogs, moles, and other animals love to eat leatherjackets and have no problem with digging up your lawn to get to them! This means you might start to notice small holes and patches of loose earth where animals have been digging for food. If your grass starts to look frail and yellowish and you notice more animals than usual looking interested in your lawn, it might be worth investigating further. Cut out a patch of dying turf in a C-shape (creating a “hinge” so you can flip the turf back into place when you’re done) and check the soil for grubs. Leatherjackets are usually found near the edge of dead patches or turf. It’s normal to find a few leatherjackets and other grubs in the soil, but if you have a severe infestation and there aren’t any other obvious causes of your lawn’s poor health, it can be time to take action.

How to Get Rid of Leatherjackets

Leatherjackets are very difficult to get rid of. There are no legal chemical treatments for them in the UK, so your only option is to use nematodes. Nematodes are microscopic parasites which latch onto leatherjackets and kill them without harming any other type of wildlife. The nematodes will then reproduce inside the dead leatherjacket and spread across your lawn, quickly stopping the leatherjacket infestation in its tracks. Using nematodes isn’t without a few drawbacks, however. Nematodes are very expensive, so if you have a large lawn you can expect to pay through the nose to treat it. In addition, nematodes are living things that will die if they don’t find a host, so you can’t just buy them at a knock-down price months in advance and stockpile them for when you need them. A much more effective solution is to prevent leatherjackets from infesting your lawn in the first place.

How to Prevent Leatherjackets

Like most lawn grubs, leatherjackets don’t like it when the soil is slightly acidic. Acidic soil will discourage adult daddy long legs from laying their eggs on your lawn in the first place, so keeping your lawn well-maintained with iron sulphate is a great way to prevent leatherjackets. Iron sulphate is a lawn nutrient that helps make grass lush, green, and soft, so it’s a good idea to use it seasonally to help your lawn stay healthy. If your lawn is healthier, it becomes naturally more resistant to disease and pests anyway, but iron sulphate also has the side-effect of making your soil slightly more acidic. It doesn’t make your soil so acidic as to be harmful to wildlife, just enough to discourage certain pests from making a home there. You’ll still find a few grubs, including some leatherjackets, beneath your lawn even if you regularly make use of iron sulphate, but there shouldn’t be enough to damage your lawn. To apply iron sulphate to your lawn, wait until some rain is forecast and sprinkle it evenly across your turf. The rainfall will water the iron sulphate down into the soil where it can work its magic! If there isn’t any rain forecast, just make sure you water the iron sulphate into your lawn thoroughly so it can be absorbed by your grass’ roots.