Leather Jackets/Crane Fly can cause extensive damage to our lawns and a recent EU legislation ban on pesticide in horticulture means from 2016 onwards we will see significant lawn pest problems.
It is always a bit hard to tell ahead of time if Leather Jacket larvae are likely to cause problems to our lawns during the forthcoming winter and spring, but following the mildest winter on record during the winter of 2015/2016 conditions have been perfect for Leather Jackets to thrive, even as we write this post in January 2016 the lawn care industry is already finding many lawns seriously affected by Leather Jacket infestation.
Up to August 2015 lawns could be treated by a licenced professional with a pesticide product called Clorpyriphos, but this product has now been withdrawn under new EU legislation leaving nothing that can easily control this Leather Jackets. In the past responsible lawn care operators would only use pesticide as a last resort once a severe Leather Jacket infestation was identified but from now on there will be no effective treatment.
For the foreseeable future what do we do if we find our lawn is suffering from Leather Jacket infestation?
A safe biological remedy, Nematodes, can be applied when the grubs are very young during August-October. Soil conditions must be wet and soil temperature above 12 degrees Celsius for the Nematodes to work therefore results can be very hit and miss, it is also almost impossible to know if you even have a Leather Jacket problem at that time of year therefore the best guide is to apply Nematodes if you notice Crane Fly active in your garden during the autumn. The live nematodes attack the Leather Jacket by entering into it via natural body openings and once inside they release bacteria into the grub which kills it. Most people do not realise they have a Leather Jacket problem until the lawn starts thinning and going bare during the spring by which time Nematodes are unlikely to be effective therefore the most effective treatment is to cover the lawn overnight with a black plastic sheet which draws the grubs to the surface of the lawn, as the sheet is removed during the morning any Leather Jackets larvae can be quickly brushed off and destroyed. This process is rather laborious and is difficult to do on large areas but it can be very effective.
More about Leather Jackets (Tipula spp) & Crane Fly
Crane Fly emerge from mature Leather Jacket larvae between August and October and mate almost straight away. Females lay their eggs into the lawn sward and it is very hard to tell how successful they have been until the larvae (Leather Jackets) become visible during the winter and into the following spring. The Larvae feed on the roots of the grass plant which causes the plant to die. Often or not most people don’t realise their lawn has a Leather Jacket infestation until the lawn starts to thin-out and become bare during the spring by which time remedial work will almost certainly be required. A good way for us to predict if it is going to be a bad year for Leather Jacket problems is to monitor when the Crane Fly are active and if the weather conditions are suitable for the eggs to survive.
During a dry autumn the eggs laid by the Crane Fly are more likely to perish than thrive which means we would expect less of a problem during the following year, however if conditions are damp and there is lots of Crane Fly activity we can expect a high chance of problems during the following year.