How to tell if leather-jacket are causing the problem patches in your lawn
The patches could also be caused by poor drainage or to much shade so it is worth checking out. Most likely the patches in your lawn are caused by an infestation of Leather jackets. Here's how to check;
Prevention is always the best cure.
The best way to control Leather-jackets is to follow the lawn-care practises outlined above. However, if your lawn is infested with leather jackets and you have checked that it is not poor drainage or to much shade causing the patches in the lawn. Let's look at getting rid of them. There are no chemical controls available to kill leather jackets. However, there is a biological treatment that will kill leather jackets by infecting them with a bacterial disease. It is safe to use for you and won't harm children, pets and wildlife.
The biological control available for controlling leather-jackets in lawns. Is a pathogenic nematode that is watered into the turf or soil and is safe for you and your children, pets and wildlife
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.
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 plants 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).