Leatherjackets are the larvae grubs of the Crane Fly (Daddy Longlegs.) Leatherjackets in lawns are a real pest and can have severe consequences unless killed. They are a pest of the lawn, for they eat the roots of the grass plants causing the grass to die.
They can also be a considerable pest in other parts of the garden - but not so noticeable - unless you have vegetable root crops - for roots of plants are their source of food until they emerge from under the ground and turn into Craneflies.
A small infestation is nothing to worry about, however if you have a lawn full of leatherjackets then the effect can be quite dramatic. In worse cases, resulting in much of the lawn dying and needing substantial remedial treatment.
Chemical control ceases to be available as from end September 2013. However, we outline a very effective measure below. If not treated, then quite a bit of turf damage can occur. It will soon re-grow, but look unsightly for several months.
Leatherjacket Approx size
First signs of leatherjacket Pests attacking your lawn are during the spring and summer, when small yellowing patches start to appear in the lawn. These eventually turn into brown patches in the grass. This is the result of the grubs feeding upon the roots of the grass. The severity of the problem is dependent upon the number of leatherjackets, and can start as just a few small patches a few inches across – hardly noticeable in an average lawn, but a considerable lawn pest if not treated - killed.
Other signs of leatherjackets in lawns will be birds pecking at the lawn to get at the grubs– mainly starlings, though members of the crow family are also partial to a feast of leather jackets - crows and magpies in particular. The birds also do a good job of aerating the lawn, for their beaks can penetrate several inches. It does no damage to the lawn.
You can do an easy follow-up analysis to see the cause, by simply lifting an area of grass where the problem exists. If it is leatherjackets in your lawn, they will be seen no more than a few inches below the turf/soil surface.
If you do not treat the leatherjacket pests, you will also see a large number of Crane flies hovering about the lawn area as the grubs emerge as Daddy Longlegs Flies.
These Adult flies then lay eggs in the lawn during autumn, which shortly hatch and start feeding on the lawn roots. The feeding normally stops in winter – unless it is mild – but soon resume again in the spring – thereby completing the cycle as above for leatherjackets in lawns.
The picture shows the damage caused by leatherjacket pests. The browning of the lawn is caused by the leatherjacket larvae/grubs, eating the lawn grass roots just below the surface. You should also be able to see a few peck holes in the top right corner.
There is a biological control by name of Nemasys. This control method - nematodes – is applied in Autumn whilst the soil temperature is still warm. The microscopic nematodes then seek out the leatherjacket grubs ‘invade’ them and destroy them from the inside!
Until recently there was no chemical treatment. However Provado Lawn Grub killer, kills Leatherjackets and also chafer grubs in the lawn. It is now available from most good garden centres. Again, this should be applied in the autumn. Late September 2013 you will nit be able to buy this, for it is being banned for garden use, Late November 2013, you will have to stop using any stocks that you have. It will be illegal to use is after that date.
There is no point in trying to treat leatherjackets in the lawn, until you are sure that they exist, but you can try the system below from late summer.
An old method – which works – is to cover the lawn area with a black plastic sheet at night in damp conditions. Peel back the sheet slowly in the morning and collect up the surfaced leatherjackets. Make sure that you peel back the sheet slowly, for if you just peel it right back, some of the leatherjackets will escape back down into the lawn to get away from the light. You then have the task of killing your leatherjacket pests!
This method can be used before you actually spot the leatherjackets damage in your lawn. Anytime after mid-summer should provide results.
For those of you who prefer to try biological control, there is a nematode available - Steinernema feltiae. The plastic sheet is very effective on lawns, but not on cropped vegetable plots!