Potato mop-top virus

In September 2018, potato mop-top virus (PMTV) was confirmed in New Zealand. Find out about the virus and what Biosecurity New Zealand and Potatoes New Zealand are doing to manage the disease.

Background on the virus and how it spreads

Potato mop-top virus is a plant virus that largely affects potatoes. It's also is a notifiable organism in New Zealand under the Biosecurity Act 1993. 

The virus is transmitted by the soil-borne fungus Spongospora subterranea that causes powdery scab, a very common disease of potatoes.   

Once established in fields, the virus can survive in the resting spores of the fungus in soil for at least 18 years. Consequently, paddocks infected with powdery scab and PMTV will remain infectious for a long time.  Eradication of PMTV in the presence of powdery scab is not possible.

The disease can be managed

While PMTV is confirmed present in New Zealand, it is a manageable disease. The disease is established in North America and Europe where it is generally managed effectively without causing major production losses. However, where it is poorly managed, it can create production problems for potato growers.

Download our fact sheet about the virus [PDF, 813 KB]

No food safety risk

There are no food safety risks from eating potatoes that have the PMTV virus. Potatoes remain safe to eat.

What's being done?

A potato sliced in half showing brown discolouration caused by the virus
A potato infected with the virus.

Biosecurity New Zealand has been working in partnership with Potatoes New Zealand to manage the discovery of PMTV. Further sampling is underway to learn more about the virus and to build a better picture of whether the disease has spread beyond the initial detections.

We are looking into how the virus may have entered the country, but we may never know.

We've removed the unwanted organism status for the potato mop-top virus. This decision was based on advice from MPI scientists and discussion and agreement between Biosecurity New Zealand and Potatoes New Zealand (PNZ).

The removal of the unwanted organism status doesn't change your obligation to report to MPI if you suspect your crops may have the virus. It is still a notifiable organism.

What you need to do

You have an important role to play in protecting your farm, your region, and the potato industry from biosecurity threats.

If you suspect you have found PMTV on your property, contact the Biosecurity New Zealand pests and diseases hotline on 0800 80 99 66.

Help control the spread of potato mop-top virus

PMTV can be spread by:

  • seed tubers
  • soil on boots and machinery
  • waste from potatoes.

That's why on-farm hygiene practices and developing a robust farm biosecurity plan are vital to try to minimise the spread. Our fact sheet has more information about good on-farm biosecurity practices.

Download our fact sheet about the virus [PDF, 813 KB]

Find out more

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