With the loss of organophosphate insecticide chlorpyrifos in 2016 as a form of chemical control of leatherjackets, farmers have had to rely much more on management to control the pest.

Grub populations in the central and southwest Scotland are at a similar level to last year, but the Renfrewshire/Dunbartonshire areas are higher than average at 1-2m plus grubs/ha, according to a survey carried out by the SRUC.

Also more than 60% of the fields contained in these areas had populations greater than 0.6m grubs/ha.

“If you are seeing crops coming through that are being affected by leatherjackets, if they have gaps within the emergence, then rolling the crop is your only option,” according to Dr Andy Evans from the SRUC.

“You can roll a crop of spring barley up to growth stage 31 without doing any damage, but the first thing to do is to go out and dig up the ground and see if you can see them.

“With the chemical control being withdrawn there is the potential of numbers building up, so farmers need to see what they can do from a management point of view.”

Prevention

When it comes to management of pastures to prevent leatherjackets developing there are some actions that farmers can undertake, according to David Michie, head of farming and land use with the Soil Association.

“One of the best things that farmers can do is to graze fields tight in the autumn, this will help to minimise tusky grass, where the crane fly will breed in the back end of the year.

“If someone is going from grass to spring barley then it can decimate the crop.

“Leatherjacket populations generally go through a cycle of a spike every six to seven years, followed by a lull, and we are currently in that low population period,” according to David.