"Seed certification has a role to play in reducing risk, but it's by no means a guarantee that it won't have diseases - you may have to go beyond the fact that it meets a certification grade," he said.
Up to 30 per cent of certified seed can contain potato virus Y, which can lead to tuber cracking, he explained. "Seed potatoes can carry a significant amount of inoculum and can spread disease in different ways."
The physiology and physical condition of seed potatoes can also affect susceptibility to pathogens and hence the uniformity, appearance and marketability of the daughter crop, he added, while frost damage "may not be apparent - you should cut open a proportion of tubers to check for damage".
Agronomist Denis Buckley said: "Potatoes aren't getting any cheaper to grow. Next year you'll pay more than £1,000 per hectare for seed."