Biosecurity New Zealand is investigating how potato mop-top virus (PMTV) could have entered the country. The agency was working with Potatoes New Zealand after the crop disease was discovered in potato tubers in Mid Canterbury, Ministry for Primary Industries incident controller David Yard said.

Two properties had tested positive for the disease, which had never before been found in New Zealand. The virus was not a food safety issue but could cause productivity issues if it was found to be widespread.

An MPI spokeswoman said that for privacy reasons, the ministry could not name the properties involved ``or their exact locations, given how small the industry is.

Potatoes New Zealand chief executive Chris Claridge said the affected variety, Innovator, was used only for potato chips: “ The industry is working closely with Biosecurity New Zealand to learn more about the virus, the impact it could have on growers, and to stop any risk of spread. We will then consider if it is possible to eradicate it, or whether we will need to work with growers to manage its impact over the long term.