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Leatherjackets (or as they are more commonly known, the larvae of daddy long legs), are the scourge of grassland farmers in the west of NI and other western parts of Ireland.
They can decimate pasture in a matter of weeks, and they usually come back to the same field year after year.
Fermanagh seems to be one of the worst hit parts of the country. The insect thrives in wet, poorly managed grassland.
My understanding is that the daddy long legs lay their eggs in wet, poached ground in August
We used to have Clorpyrifos-based products (Dursban) available that were excellent at controlling the leatherjackets but in 2015 the EU decided to ban the use of these products. So we were cut loose and, to date, no other product has become available to control this pest.
My understanding is that the daddy long legs lay their eggs in wet, poached ground in August.
They seem to like plenty of cover so rushes, weeds or heavy swards of grass are ideal.
The eggs hatch into worm-like larvae and they feed on the roots of the grass during the winter and early spring. Eventually they kill the sward.
Patches
The first we farmers know is when we go out in the springtime and discover patches of fields with little or no grass. This would be the ideal time to spray the ground, but that is now illegal.
At this stage there is really very little we can do.
There are other schools of thought that sowing fertiliser or spreading slurry will kill them, but I would be very sceptical of this
There are suggestions that using a heavy roller at night will squash them (they seem to come to the surface at night) but pulling a heavy roller over this type of soil is not ideal.
There are other schools of thought that sowing fertiliser or spreading slurry will kill them, but I would be very sceptical of this.
Improve
Over the last 10 to 12 years, I have tried to improve my grassland management. I try to graze down tight and cut paddocks regularly which ensures that there is not much cover on my pastures during August.
All this seems to have helped and I did not have any serious problems with leatherjackets for seven or eight years.
On this farm, the improvement in grassland management has compensated for the removal of the only product capable of controlling these pests.
Wet
However, last year August was very wet and ground conditions very poor. It meant that good grassland management was impossible.
There was no way that I could get the paddocks cleaned out the way I wanted or cut for silage. I was building covers of grass in preparation for the autumn, but conditions just got worse.
I have several fields with bare patches, something that has not happened here for a while
This was ideal for the daddy long legs to lay their eggs and they seem to have been busy.
This spring they are back with a vengeance. I have several fields with bare patches, something that has not happened here for a while.
I actually had forgot what this looked like, and while I tried to convince myself that it might be some other issue, I quickly had to accept that the pest had returned. I dug several holes, and it was not hard to find the culprits.
Mitigation
I am involved with a group of farmers and scientists who have been looking into leatherjacket mitigation strategies. To be honest I felt like a fraud when I joined the group as I thought that I had eliminated the problem on my farm.
I still believe that grassland management can go a long way to eliminating a leatherjacket problem
But like most things, when you let your guard down there is always the chance of being brought down to earth with a bump.
I still believe that grassland management can go a long way to eliminating a leatherjacket problem, but we will need something else to help out when our best efforts have failed.
There is always going to be years when the weather will work against us, and that is when we need a reliable method of control.
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