Leatherjackets are a brown grub-like blight on many UK lawns causing clusters of yellowing, dead grass. If leatherjackets are present in your lawn, you may also notice birds attacking your grass trying to eat them (Starlings are particular fans of this delicacy!).
You can easily diagnose if your lawn is suffering from leatherjackets by pulling up the suspect yellowing turf that is being targeted by birds. This will reveal if these terrible tenants have moved into your lawn as they will be easily visible.
What causes leatherjackets to appear?
Leatherjackets hatch from eggs laid by crane flies, also known as daddy long legs. Crane flies will lay eggs in most UK lawns and some may never hatch – but if conditions are wet and damp for a considerable amount of time (a wet winter) this will cause them to hatch and begin to live under your lawn. They will then continue to thrive in poor draining lawns, as conditions remain damp and ideal for them to live in.
Can I prevent leatherjackets?
Yes – you can’t stop crane flies from laying eggs, but you can prepare your lawn to deal with wet winters that are most likely to produce living leatherjackets at a later stage. If you find that your lawn suffers from poor drainage (water pools on the surface regularly) then you should try to aeration. Aeration is simply the process of creating holes or pockets of air in the soil to allow it to breathe and encourage the flow and dispersal of rainwater.
My lawn has leatherjackets now, what can I do?
There is no chemical pesticide to eradicate leatherjackets at present. Nematodes are microscopic bacterial worms that get rid of leatherjackets by infiltrating their outer casing and subsequently killing them. There are a wide variety of nematodes on the market, but it is important to make sure you have the right nematodes for the pest you are experiencing. For leatherjackets, the correct nematodes are Steinernema feltiae. Products such as Nemasys can be applied to the infected area or all across the lawn and must be watered in to activate the nematodes. Always follow the instructions on these products.
But what about my grass?
Once you are certain you have eradicated leatherjackets from your lawn, it's time to repair the mess they've left behind. You can read more about how do that, here.