Monday, 6 May 2019
Name: Potato spindle tuber viroid (PSTVd)
Symptoms are highly variable depending on host, viroid strain and environmental conditions.
Many ornamental species are asymptomatically infected, such as Brugmansia suaveolens, Dahlia sp., Solanum laxum and Streptosolen jamesonii ‘Yellow’.
Mild strains cause few if any symptoms on the foliage, especially in the earlier generations. More severe strains can cause plant stunting, upright growth habit and, when viewed from above, clockwise phyllotaxy. Leaves are often a darker green than normal, rugose and distorted. Tubers are elongated (or spindle-shaped) and may have surface cracks and very prominent eyes.
Mild strains may not cause any symptoms, while severe strains cause plants to appear stunted and bunched due to shortened internodes. Leaves are small with yellowing and purpling, down curling and twisted. Flowers may abort. Fruit size is reduced and ripen erratically.
Transmission: Seed transmission and trade in vegetatively propagated plants are the main methods of long distance dispersal of the viroid. The viroid is readily mechanically transmissible, and once introduced to a site, can be carried on people’s hands or on pruning tools and can even be transmitted when leaves of neighbouring plants brush against each other.
Favoured by: Delays in recognition of infections.
Host range: Reported natural hosts belong to the Solanaceae, Asteraceae or Amaranthaceae (syn. Chenopodiaceae). Ornamental plant species that are natural hosts include Brugmansia spp., Calibrachoa sp., Chrysanthemum sp., Dahlia sp., Lycianthes rantonnetii, Petunia x hybrida, Solanum laxum (syn. S. jasminoides) and Streptosolen jamesonii. Capsicum, tomato and potato are important vegetable hosts.
If this species is suspected it should be reported to your local biosecurity agency or call the emergency plant pest hotline: 1800 084 881
For further information please refer to the industry Pest ID Tool at www.pestid.com.au
Note that the Pest ID tool is now available with free access to industry.
An initiative of the Nursery Levy funded National Nursery Industry Biosecurity Program (NY15004) and ‘Building the resilience and on-farm biosecurity capacity of the Australian production nursery industry’ Project (NY15002).