Leatherjacket control in lawns: Leatherjackets

Leatherjackets will now begin to pupate and their pupa casings will prevent Leatherjacket Killer Nematodes from attacking them. The next time the Nematodes will be effective is in September, when the Crane Fly have laid their eggs into the lawn and the new Leatherjackets have hatched. Please read on for more information about Leatherjackets and how Nematodes are a safe and effective treatment for them.

We hear a lot about global warming and the effects it might have. Even relatively small rises in average temperatures can mean the difference between success or failure for certain species. And the recent warm, damp autumns and winters have certainly favoured leatherjackets. So it's important to be on the lookout for daddy-long-legs from late August and be prepared to act.

If these conditions occur, apply Leatherjacket Killer at any time from late August to the end of October.

An autumn 2007 survey revealed that leatherjacket numbers were again high and lawn owners, particularly in the south of the country, should anticipate risk of damage by leatherjackets.

Although average leatherjacket numbers were down on 2005 levels at 97.1 per m2 they were still significantly higher than the long term average of 69.7 for all survey sites in the period 1992-2006. Regionally, average numbers of leatherjackets have fallen in the Midlands and north but in the southern region they are 28% higher than in 2005 and the highest since 2001.

Adequate soil moisture in the autumn is critical for the survival of cranefly eggs and newly hatched leatherjacket larvae. All counties experienced heavier than average rainfall in late August, and apart from a warm dry week ending 12 September 2006, the weather in autumn 2006 has been conducive to egg and young larvae survival.

"We have been routinely monitoring leatherjacket numbers, via an independent organisation, since 1992," explains Andy Cawley, Sales and Marketing Manager, Dow AgroServices.

"Monitoring helps groundsmen and lawn owners plan control measures against leatherjacket damage. It certainly helped alert them in 2006 when 2005 survey figures revealed exceptionally high numbers of leatherjackets in the soil."

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Leatherjackets are the larvae of the Crane fly, more commonly know as Daddy Long Legs. Crane flies emerge from their pupa casings from late July through August, at which time they mate and lay their eggs within 3 weeks. These eggs mature quickly, hatching into leatherjacket larvae through August and September. Although the damage may not be too apparent at first these larvae will immediately start feeding on grass roots. As temperatures drop going into the winter the larvae will reduce their feeding and wait for the warmer spring weather to arrive. It is at this time that the damage will start to become apparent with turf turning yellow in patches and thinning out. By the end of May the larvae start to pupate and then hatch as adults in July / August and the Daddy Long Legs will emerge again for the cycle to continue.

There are several methods to see if you have leatherjackets in your lawn. Firstly you may notice starlings, crows and even foxes in bad cases pecking or scratching your lawn. This behaviour will help you pinpoint bad patches in your lawn allowing you to go in for a closer look.

Take a spade and dig approximately 1 -2 inches into the soil. If leatherjackets are there they will be in amongst the turf mat or just below it. During the night they can come up to the surface and feed on the succulent crowns of turf grasses causing maximum damage. On some mornings with heavy dews they can be seen crawling on the turf.

If this doesn't work then mix some lemon washing up liquid in a bowl of water and tip it out onto approximately 1m2. The washing up liquid has a suffocating effect on soil organisms, forcing them to the surface.

Some people try the following method to reduce leatherjacket numbers. Take a large black polythene sheet and place it over the suspected infestation. Leave the cover on overnight. In the morning peal back the cover a little at a time and collect the leatherjackets as you go. This will work best on warm nights from May to early June when the leatherjackets will be at their largest, fattening themselves up ready for pupating. However, by then much of the damage has already been done. This is not a reliable method of eradicating leatherjackets.

The control of leatherjackets has been made harder by the ban of certain pesticides that are harmful to the environment. There are lots of natural predators of the leatherjacket such as starlings and even mites but the sheer number of larvae is often overwhelming. The best method of control is to use nematodes to kill them when they are at their weakest, which is when the eggs have just hatched into larvae around September/October.

The great thing about nematodes is that they are completely safe to humans and animals. One new pesticide on the market today, advertised for use on leatherjackets, contains the active ingredient imidachlorprid which is harmful to bees. Bees have an extremely important role to play in food production and plant growth, and with native species constantly under threat from parasites and other predators, it's important not to make life any harder for the bee. It's a shame that pesticides are promoted which are harmful to insects, when nematodes do an equally good job without causing any environmental damage.

Leatherjackets and Leatherjacket control