Potato spindle tuber viroid (PSTVd)

Potato spindle tuber viroid

Avocados and potatoes are important export crops for New Zealand. If potato spindle tuber viroid established here, it would reduce crop yields and overseas markets might reject our produce.

About Potato spindle tuber viroid (PSTVd)

This viroid causes disease in plants from the tomato and potato family, avocados, and some ornamental plants (like dahlias, chrysanthemums, and petunias).

It has been found in many parts of the world, including Europe, Central and South America, and Africa. It's often present in countries with similar climates to New Zealand. Some countries, including the USA, Canada, and the Netherlands, have eradicated it.

Global distribution of Potato spindle tuber viroid

World map showing distribution of the viroid

Why this is a problem for New Zealand

The disease stunts potato and tomato plants, reducing crop yields.

If this disease established in New Zealand, it could also affect our exports.

The viroid can be spread from plant to plant:

  • by an aphid, Myzus persicae, which is widespread in New Zealand. For the aphid to carry the viroid to a new plant, the original plant must be infected with potato leafroll virus (PLRV) as well as PSTVd
  • through contact with infected plant material
  • from infected seeds or pollen.

Map of New Zealand showing where PSTVd could establish

How it could get here

Potato spindle tuber viroid could arrive on:

  • seeds for planting or nursery stock
  • fresh fruit and vegetables (like tomatoes or avocados).

Biosecurity New Zealand has strict measures in place to limit the chances of the viroid making it through the border.

But we need you to be vigilant, too. Whenever travelling to New Zealand, always declare any fruit, vegetables, or seeds in your luggage. If you don't, you could face a $400 fine.

How to identify Potato spindle tuber viroid

Left: Comparison of infected smaller potatoes with larger healthy potatoes. Right: Healthy potato next to 2 spindly diseased potatoes.
Images: EPPO Global Database  

Infected plants may show no signs of disease but have a lower than normal yield.

Visible signs in affected plants can include:

  • stunted plants
  • fruit not ripening
  • spots or streaks of dead tissue on fruit
  • yellow or grey leaves.

In potatoes:

  • symptoms get worse with each generation
  • infected plants are spindly and small
  • leaves can roll, turn yellow, or die
  • the potatoes are very spindly and small with growth cracks.

In tomatoes, fruit may:

  • be small
  • have dead spots and streaks
  • not ripen normally.

What to do if you suspect the disease

If you think your plants are showing signs of Potato spindle tuber viroid:

Note: This information is a summary of this disease's global distribution and potential impacts to New Zealand.

Last reviewed: