Leatherjackets In Lawn: How To Spot And Treat Grey Crane Fly Larvae In Your Grass

The last thing we want to be talking about after spending the summer watching our grass dry out is the prospect of another lawn-related threat.

But as the weather starts to get wetter and cooler, gardening experts are warning that crane flies (which you might also know as daddy longlegs) are laying their eggs right about now.

These eggs then hatch into larvae called leatherjackets, which Jonathan Davis from Lawnsmith has dubbed “the pest behind one of the most damaging lawn problems”.

“Right now, those eggs are just sitting below the surface [of your lawn], waiting for cold and wet conditions to hatch into leatherjackets,” he said.

Once hatched, the greyish brown grubs “can be a nightmare for your lawn”, he added.

“An infestation can undo all the hard work you’ve put in and leave you with nothing.

“They thrive by eating the roots of grass and plants, killing their food source as they go. Because they live under the surface, gardeners often don’t notice a problem until months later…”

Basically, they’ll spend autumn and winter munching your lawn roots and then, come spring, you’ll start to see the effects.

The key thing to look out for is patches of lawn that start to die, wither or go yellow.

Obviously, after an intensely dry summer and prolonged drought, lawns everywhere are already looking yellow and patchy.

But generally, grass should be growing back by now. Once it has revived itself, it’s important to keep an eye on whether it stays looking green and verdant or begins to die off again – especially come spring.

Davis said “a leatherjacket infestation could be the final blow to your lawn’s health” after the intense summer we’ve had, and suggested prevention is easier than a cure.

Per the Royal Horticultural Society (RHS), a good way to tell whether you have a leatherjacket infestation is to place a light-blocking material, like black polythene, on a watered lawn overnight. If leatherjackets are there, the next morning, they’ll typically be found on the lawn surface under the cover.

Not all leatherjackets will noticeably affect your lawn. According to the RHS, only a small number may actually cause damage, so if you’re not bothered by them, you could just leave them alone so birds and other animals can feast on them.

The small grubs love lawns with poor drainage, according to Davis, who said addressing that now could help prevent an infestation taking hold. “Aerating your lawn can help improve drainage. To do this simply create holes in the turf to allow it to breathe and encourage water to disperse,” he suggested.

Another idea is to remove thick branches of overhanging trees and bushes to help more sunlight reach the turf.

“Some soils are better than others for drainage. For example, nutrient-dense clay soils can make gardens more prone to flooding,” he added.

“If you often see water pooling in your garden, investigate the type of soil so you know how to nurture the lawn correctly.”

And if you’re especially worried about your lawn, you can preemptively treat it with nematodes (specifically ‘Steinernema feltiae’) which “get rid of leatherjackets by infiltrating their outer casing and subsequently killing them”.

But it’s worth noting these don’t work so well in cold weather so the best time to apply them is in September and early October.

If, come spring, you do notice patches of yellow and browning grass, the gardening pro said removing the dead grass and re-seeding the area is your best course of action. Applying fertiliser across the whole lawn can also help maintain its overall health and help its recovery.Good luck!