Potato spindle tuber viroid: declared pest

Page last updated: Wednesday, 6 July 2022 - 7:58am

Please note: This content may be out of date and is currently under review.

Potato spindle tuber viroid (PSTVd) is a declared pest in Western Australia. It can significantly reduce crop yields in potatoes and tomatoes.

Potato spindle tuber viroid is a serious plant disease that affects the growth of plants, mainly tomatoes, potatoes, ornamentals and solanaceous weeds. PSTVd is generally symptomless in ornamentals and weeds. 

Use certified disease-free planting material, destroy infected plant material, and employ on-farm biosecurity practices to prevent unwanted diseases, pests and weeds from entering your property. By doing so, you will also protect Western Australia's agricultural industries.


PSTVd was first reported as a disease in potatoes in North America and first detected on tomatoes in South Africa. The disease is reported to occur in Asia, Africa, North America, South America, and Europe.

There have been previous detections and eradications of PSTVd in Australia, including in Western Australia.

Agricultural and economic impact

Yield and quality losses

The yield of marketable potatoes and tomatoes from affected plants can be significantly reduced, but varies with plant age, age when infected and disease severity. There have been reports of yield losses in potatoes of up to 65% and of 1060% in tomatoes due to PSTVd.


Various changes in growth habit and to foliage, roots, flowers, and fruit occur in plants infected with PSTVd.

Symptoms may be confused with those of nutrient imbalance, spray damage, insect damage or other plant diseases such as true viruses.

Some infected plants may have no visible symptoms. The severity of symptoms can vary due to different strains of the viroid.

On potatoes

Foliage symptoms are often difficult to recognise and are rarely distinguishable before maturing.

Potato tubers affected with PSTVd are smaller and deformed compared to healthy potatoes

(L) infected potato tubers; (R) healthy potato

  • Stems are upright with internodes longer and more slender than normal.
  • Leaflets are twisted, wrinkled and slightly smaller than normal with fluted margins.
  • Leaves near ground level are held in an upright position in contrast to leaves of healthy plants that often rest on the ground.
  • Tubers are elongated with pointy ends. Eyes are deep and more prominent; surface cracking may occur.
  • Tubers of some cultivars develop knobs and swellings and are severely misshapen.

Foliage and tuber symptoms become more severe with each generation.

On tomatoes

Infected tomato plant on left compared with healthy plant on right. Plant is much smaller.

(L) Infected tomato plant; (R) healthy plant

  • In mature tomato plants, infection with severe PSTVd strains causes purpling and yellowing of the leaflets, shortening of leaflet internodes resulting in a ‘bunchy top’ effect, leaflet down-curling and twisting and general plant stunting.
  • Spindly shoot growth can occur.
  • Flowers may abort.
  • Fruit can be dark green, fail to ripen normally and have thicker outer walls.


Disease transmission occurs between plants through contact of the sap from small wounds in the leaf of a diseased plant to a healthy plant.

Initial introduction of the viroid into potato and tomato crops is mostly through infected seed.

Spread can occur through

  • handling of plants
  • movement of animals and machinery through a crop
  • cutting tools
  • clothing

Transmission also occurs through pollen but only to the seeds pollinated, not to the whole plant. Transmission is also reported by aphids if the source plant is also infected with Potato leafroll virus.

Prevention and control

There are no products to prevent or treat PSTVd infection.

Control is achieved through strict biosecurity measures, including the appropriate destruction of infected plant material and the sanitation of tools and production facilities.

To prevent infections:

To reduce spread within a crop:

  • Limit the movement of machinery, vehicles and people:

    • between infected areas and uninfected areas.
    • entering production areas.
  • Clean machinery, vehicles and equipment after any contact with an infected area and between paddocks.
    • Wash cutting tools in a solution of 2% sodium hypochlorite after use.
    • Change or sterilise clothes and shoes when moving from areas where PSTVd is present into clean areas.
  • Wear vinyl or latex gloves when handling infected plants and change gloves regularly.
  • Always work in clean areas first and then move to infected areas.
  • Remove crop plants infected with PSTVd, and those nearby that could be recently infected.  Deep bury or burn them rather than cultivated back into the soil after harvest.
  • Control weeds and volunteer plants that can be sources of infection.

Status in Western Australia

Potato spindle tuber viroid is a prohibited organism under section 12 of the Biosecurity and Agriculture Management Act 2007.

Western Australia's Regional Pest Freedom for PSTVd is supported by general and specific surveillance. A person who finds or suspects the presence of PSTVd must report it to DPIRD.

Report suspect disease

Early detection and eradication will help protect Western Australian tomato and potato growers. Please make a report on MyPestGuide or contact the Pest and Disease Information Service (PaDIS).

Samples of suspected PSTVd infected leaves or tubers can be sent for testing to DDLS-Plant Pathology. Complete the Potato virus identification form clearly marking the ‘Potato spindle tuber viroid PCR test’ and writing ‘suspect potato spindle tuber viroid’ in the comments section. 


MyPestGuide® Reporter contacts

Contact information

Pest and Disease Information Service (PaDIS)
+61 (0)8 9368 3080