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The question I get asked most about lawn care, 

What is causing the bare patches in my lawn?

The patches in your lawn are probably caused by leather jackets 
  • Leather jackets are the larvae of the Crane fly, more commonly known as Daddy Longlegs. 
  • This article will show you how to identify the cause and how to deal with an infestation of Leather jackets.
  • How to prevent future infestations.
  • The patches could also be caused by poor drainage or to much shade so it is worth checking outbut most likely it is an infestation of Leather jackets dealt with on this page

Prevent and control Leather jackets from ruining lawns

Prevention.

Prevention is always the best cure.

  • To Prevent leather jackets infesting lawns it is good "lawn care" practice to encourage the grass to root deep by avoiding over feeding with chemical feed and over watering. 
  • Leather jackets are attracted to shallow rooted grass 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.

Control leather jackets 

  • The best way to control Leather-jackets is to follow the lawn-care practises outlined above, but if your lawn has attracted leather jackets there are no chemical controls available. 
  • To control leather jackets use Nematodes that kill them by infecting them with a bacterial disease it is safe to use for you and your children, pets and wildlife.

How to kill Leather-jackets. 

  • The biological control available for controlling leather-jackets in lawns and the method I use is a pathogenic nematode which is watered into the turf or soil and is safe for you and your children, pets and wildlife
  • 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.

Non-chemical control is the only way to kill leather-jackets as there are no chemical controls available.

When is the best time of the year to kill leather-jackets? 

Autumn- September and October  is the best time to apply when grubs are present, soil is moist and soil temp is above 10C. Best applied after crane flies (daddy long legs) have emerged and are laying fresh eggs in the grass. This normally happens from September 

This is the autumn treatment I use and recommend for clearing Crane fly larvae from lawns. Leather jacket treatment

  • Kills leather-jackets in lawns safely and effectively. Lawn may be used immediately after application.
  • Safe for you and your children, pets and wildlife
  • Apply when grubs are present, soil is moist and temps above 10C.
  • Grass cutting, fertiliser application and weed control can carry on as normal
  • .Apply by watering can or hose end feeder. 

What are Leather Jackets? What attracts them? Why are they a problem?

  • 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 grass 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.
  • Leather-jackets have elongate tubular bodies, up to 30mm long, and are greyish brown. They have no legs or obvious head. 

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 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. 
  • 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.
  • Dry soil conditions post egg laying can result in many of the eggs failing to hatch, so the presence of large numbers of adult flies do 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 patches 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.

More information 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.

Beneficial nematodes

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).

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