The highly-contagious disease ring rot has been found in a batch of potatoes sent to a pack house in East Anglia.

The potatoes – of the variety Sante – came from a Herefordshire grower.

They were being packed at a Cambridgeshire firm when suspect symptoms were identified.

The firm notified Plant Health and Seeds Inspectorate last Friday (30 July).

Officials then arranged an immediate visit and tests using two methods were conducted at the Central Science Laboratory on Saturday (31 July).

Ring rot was confirmed by both testing methods – immunofluorescence (IF) and polymerase chain reaction (PCR) – which gave positive results.

An eggplant test, as required under European legislation, will now be carried out.

But government officials said on Monday (2 August) that there was no doubt about the results of testing already carried out.

Widely regarded as one of the most serious diseases of potatoes, ring rot is spread by infected tubers and on contaminated machinery and equipment.

Annual losses have been as high as 50% in the US.

The Department for Environment, Food and Rural Affairs said the East Anglian firm had acted “promptly and responsibly”.

It also reported “good co-operation” with the grower concerned.

Holding action had been taken to prevent the use or movement of material or equipment which may present a risk, said a Defra spokesman.

A tracing and testing programme has been initiated.

This will include an investigation into the origin of the potatoes that were supplied to the grower in Herefordshire.