Testing is ongoing to determine the spread of the potato mop-top virus, with four properties confirmed to have the virus and another ten being tested.

The virus largely affects potatoes and is a notifiable organism. It was found on two properties in Ashburton District last month.

It is transmitted by soil-borne fungus that causes powdery scab and can survive long-term only in the potato plant or in the fungus.

Once established in fields the virus can survive for up to 20 years in soil but if found to be established in NZ it is a manageable disease.

PMTV is established in North America and Europe where it is managed effectively without causing major production losses but where it is poorly managed it can create a production problem for potato growers.

Potatoes NZ’s latest industry update reports extensive testing is ongoing with 3593 tubers producing 41 positive samples, 38 of variety Innovator and three of variety Russet Burbank.

All samples tested are from the previous growing season.

BiosecurityNZ has also started testing potatoes from North Island growers.

Seed lines for the 2018-2019 crop are being tested and are all negative so far. Testing of the Innovator, Russett Burbank and Agria seed lines is complete and are all negative. Sampling for Nadine and Moonlight seed lines is continuing.

The main focus is to understand the risks associated with the possible establishment of PMTV in NZ and to minimise its impact.

Investigative work is under way to understand virus distribution and affected crops to formulate options to manage, contain or eradicate and to limit and contain infection to known paddocks and processing plants, particularly focusing on processing waste contamination.

PotatoesNZ said stakeholders are being informed of potential issues while creating minimal industry and public alarm.

The investigation is looking to determine if an import pathway can be identified.

The Ministry for Primary Industries has assured the industry all possible pathways of introduction are under investigation as is the development of long-term planning options.

In agreement with BiosecurityNZ and PotatoesNZ MPI’s chief technical officer has now removed the unwanted organism status for the virus.

The removal of the status does not affect the obligation of growers to report to MPI if they suspect crops might have the virus as PMTV is still a notifiable organism.

PotatoesNZ said it has now been agreed MPI will transition the response into an industry-led management programme while supporting the industry to achieve agreed outcomes.

Technical workshops are being planned with dates and venues to be announced soon.

The workshops will cover what symptoms to look for, how to submit tubers for testing and provide a response update.


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