Potato growers in Angus have been warned they are sitting on a timebomb and need to act now to avoid potato cyst nematodes (PCN) endangering their crops.
A scientific paper, to be presented by John Pickup, of the Scottish agricultural science agency, to the Crop Protection Northern Britain conference in Dundee later this month, will reveal an alarming surge in PCN infections in farmland south of Aberdeenshire.
The nematodes are highly destructive and infestations can in extreme cases cause entire crop losses.
Angus has, however, seen the biggest rise with PCN infestation now in excess of 6% of soil samples.
Stuart Wale, the potato specialist at rural college SRUC, said growers needed to wake up to the scale of the potential problem and act immediately.
He told the SAC Association of Potato Producers’ conference at Perth that new more demanding testing for PCN lay behind some of the increase. But the progressive switch from high-grade seed to ware potato production was also at the root of the problem.
He added: “Historically we’ve always had much lower levels of PCN quite simply because we’ve traditionally been a seed-producing region and had that long rotation history between crops.
“But things have changed. We’re now at only 40% seed on 11,000 hectares (27,181 acres). There is now a much bigger area in ware.”
Mr Wale said until the new EU-wide testing regime came into force three years ago Scotland had only 2% of fields downgraded because of PCN infestation.
Mr Pickup’s paper will show the figure has jumped to 5%, with Angus showing a more alarming rise. The area north of Aberdeen remains relatively free at just 1% on average.
Mr Wale said historically PCN in Scotland had been restricted to the globodera rostochinensis nematode.
Confirmed globodera pallida infestations had, however, been discovered and that was far worse as it was much more difficult to control.
PCN already causes huge problems for growers in England and control has not been helped as the EU has banned several of the active chemical ingredients previously used to tackle them amid worries over their persistence in the soil and impact on the environment.
Mr Wale said ware growers needed to think about extending potato crop rotations to a minimum of one every five years. One crop in every six would, however, be better.
Removing volunteer potatoes from crops in fields following tatties was also critical, albeit he recognised the difficulties of ensuring that happened in rented land.
There are already varieties resistant to rostochinensis. Others with pallida resistance are also emerging.
Mr Wale warned: “If we are not careful we are going to end up in trouble. Where you have PCN, then assume there’s pallida, even if the results show just rostochinensis.”
Mr Wale said nematicides are most effective when used with a bed tiller and the chemical is trickled into the top 15cm (6in) of the seedbed.
Brechin-based seed grower Alistair Melrose, of A.J. Allan Potatoes, said PCN infestations were a very real concern.
“I’d urge all those affected to do as much as they can to reduce PCN populations because it is in all our best interests that this happens,” he added.