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It is the question I get asked most about lawn care,
This article will show you how to identify the cause, how to deal with Leather jackets and measure to prevent future infestations.
Tips to prevent and control Leather jackets from ruining lawns.
Prevention is always the best cure. To Prevent leather jackets infesting lawns, encourage the grass to root deep by avoiding over feeding with chemical feed and over watering.
To control leather jackets follow the tips on this page and use Nematodes that kill them by infecting them with a bacterial disease.
What are Leather Jackets?
They are the larvae of the Crane fly, you might know them better as Daddy longlegs. From July through till September the adult Crane fly "Daddy long legs" can lay hundreds of eggs in your lawns. The eggs hatch between late autumn and early spring into a maggot like leather jacket larvae and it's these that eat grass roots and ruin the lawn.
The eggs hatch a few weeks after they have been laid and the leather-jackets immediately begin feeding on plant roots. In cold winters, they overwinter as small larvae and do not grow large enough to cause significant damage until mid-summer. Mild winters allow the young larvae to continue feeding and they can be large enough to cause lawn problems by late winter.
How are Leather jackets a problem in a lawn?
The larvae feed on the grass roots and shoots and can strip large areas of a lawn in just a few days, leaving bare patches that quickly become colonised by weeds or moss.
What attracts them to my lawn?
Over watered and chemically fed lawns can be effected most because over watering and feeding encourages the grass roots to stay near the surface rather than grow deeper looking for the food and water you are providing, making them an easy target for the Leather jacket.
Newly laid turf can attract the adult Crane fly.
A new lawn is also susceptible to damage by the Crane fly larvae as the roots are succulent and easy to digest by the larvae.
What are the ideal conditions for an infestation of Leather jacket?
A combination of poor grass condition, shallow rooting and mild wet winters create the ideal conditions for hatching of the Crane fly larvae. Deep rooted grass, low winter temperatures and frosts usually control numbers.
Dry soil conditions post egg laying can result in many of the eggs failing to hatch, so large numbers of adult flies does not always mean there will be large numbers of larvae or leather-jacket in the next year. A good reason not to over water your grass.
How to tell if leather-jacket are causing the problem in your lawn.
These are the signs to look for in a lawn infested with Crane fly larvae.
The lawn develops patches where the grass turns yellowish brown and eventually dies off. To check this is caused by an infestation of Leather-jacket and not grass diseases, poor soil, over feeding/watering or drainage problems dig up a shallow section of the affected turf and look for Leather-jackets in the soil.
Another way is to soak the lawn with water and cover it with black polythene, leave it overnight and when you lift it the next day you will see large numbers of grubs on the surface of the grass.
Recognising Leather-jackets (Crane fly larvae)
Leather-jackets have elongate tubular bodies, up to 30mm long, and are greyish brown. They have no legs or obvious head.
Don't encourage the grass to root shallow, avoid chemical over feeding and pointless watering.
How to kill Leather-jackets.
The biological control available for controlling leather-jackets in lawns and the method I use is a pathogenic nematode, Steinernema feltiae, which is watered into the turf or soil. The nematodes enter the bodies of leatherjackets and infect them with a bacterial disease which kills them.
Nematodes will kill and clear an existing infestation of Leather-jackets and as a preventive measure nematodes can also be applied in September to early October. Follow the clear instructions on the pack for best effect.
More about using biological controls: Nematodes
The Nematoda, known as nematodes, roundworms or eelworms are a very diverse phylum of animal. There are more than 25,000 described species, and they are found in almost every habitat. Most are microscopic and many are important components of soil and marine ecosystems. More than half of the described species are parasitic on plants or animals and some species such as the potato cyst nematodes (Globodera species) and leaf and bud eelworms (Aphelenchoides species) are plant pests.
Some of the microscopic species of nematode that can infect insects and molluscs have been developed for pest control. These species pose no risk to plants or vertebrates. They work by entering the invertebrate’s body and releasing bacteria. This results in an infection causing the death of the invertebrate, the nematodes then feed and multiply on the decomposing body.
Using nematodes correctly
These nematodes come in packs that are mixed with water and watered onto affected plants and soil. Like other biological controls there are limitations which must be understood if they are to work well. Being living organisms they should be used as soon as possible after they are purchased or received and all manufacturers’ instructions followed.
The nematodes require moist conditions and so are best applied in cool and damp conditions. There are also temperatures restrictions with different species requiring temperatures above 5ºC (41ºF) or 12ºC (54 ºF).