I received this interesting question in July 2020 about lawn seeding after leatherjacket damage. It was posted as a comment on my Leatherjacket Lawn Pests – The Complete Guide blog post, but I thought it needed expanding on.
We have now removed all the grass from a 25 square metre area along with well over 1000 leatherjackets.
However, when we dig down to a depth of 4-6 inches we are still finding lots more so our current plan is to rotavate the area this week to clear as many more as we can find with a view to then reseeding a new lawn.
It would be helpful to understand the best timings from here to sow new seed that will also give us the best chance of avoiding a repeat attack.
Should we re-seed immediately or should we now wait until after any crane flies have stopped laying eggs this time around? Do they actually lay their eggs on the soil or do they find grass to lay their eggs?
Any guidance would be gratefully received.
Thanks for your question.
Well done on completely renovating your lawn after a leatherjacket attack. You should achieve a great lawn with such thorough preparation of the soil.
Seeding your lawn after leatherjacket damage?
As a professional, I would prefer to take into account the weather, rather than potential leatherjacket infestation. Timing of lawn seeding can be a key to success. You asked this in July 2020, so midsummer in the UK. Summer can sometimes be too hot for young grass and it can dry out very quickly. If you are not able to water a new lawn in it’s first couple of months, and the weather is sunny, you may have disappointing results.
However, you do have the advantage of plenty of time left in the growing season. So, if your leatherjacket repair does not work out, you can try again safely in the autumn. Save some seed after your first sowing so that you can patch it up seamlessly with the same grass if you need to.
Crane flies like to lay their eggs in thatchy, long grass. This is why thick turf is often a common target for the pests. A new, thin lawn is not a desirable environment for them. They need a food source for their young which is organic matter. In this case grass leaves and roots. Crane fly adults often blow into corners of gardens and are forced to lay eggs in any patch of soil. So there is still some risk, depending on the layout your particular garden. Personally, I would not delay seeding after leatherjacket damage.
Crane fly pests
Crane flies are an annual pest. Numbers from year to year strongly correlate to the environmental conditions. The winters of 2018/19 and 2019/20 were mainly warm winters following wet late summers. This is the ideal conditions for them and their numbers rocketed. If we experience a dry summer and cold winter in 2020/21, they may not be such a problem. But who knows what will happen?
Some people do claim to have them for many years. If true, this is very rare indeed.
The best thing to do would be to seed your lawn as soon as the soil is ready, and then be vigilant over the winter. At the first sign of any leatherjacket activity or thinning of the lawn start utilising some deterrent methods to reduce their numbers. Hopefully damage is kept under control before it is a problem.
I hope this is a useful answer. Good luck with your new lawn!
The Lawn Man