"The potential is there for something really horrible to happen," he told the council's Winter Forum in Shropshire last month (23 January).
Burns called on growers to source seed from the continent "only as a last resort", adding: "Varietal availability is not there in the UK and won't be for a number of years. If you must, source from areas known to be root rot-free. The Dutch polders carry a higher risk."
He put the cost of allowing ring rot to establish in the UK at around £13m "at a conservative estimate, and not counting the high reputational damage to the export sector".
The Potato Council's Safe Haven seed certification scheme was originally introduced following an outbreak of ring rot in 2004. A further outbreak in 2012 was also safely contained.
Richard Austin Agriculture head of trials Dr John Keer told the forum that risk of early blight (Alternaria spp.) is on the rise and can lead to yield losses of up to 30 per cent. "The predicted warmer summers will favour it and meanwhile we are losing broad-spectrum controls - when the Swedish growers lost Mancozeb, there was an explosion of Alternaria," he pointed out.
"We are also growing more susceptible varieties such as Markies and Vivaldi, and there are more virulent strains about."
For those growing such varieties, Keer urged: "Plug Alternaria control into your late blight (Phytophthora infestans) control regime. The best late-blight fungicides don't control Alternaria on their own."
Fortunately, 2013 saw a historically low incidence of late blight, said Potato Council blight specialist Gary Collins. But he appealed for more potato growers to act as "blight scouts" in under-represented regions.