Following the identification in 2006 of Potato spindle tuber viroid (PSTVd) in the UK and several other EU countries, in the ornamental species Brugmansia and Solanum jasminoides, a survey for this harmful viroid was initiated. A second closely related viroid, Tomato chlorotic dwarf viroid (TCDVd) has now been identified for the first time in the UK by laboratory testing of imported petunias. As a result of these findings, the UK PSTVd survey will be extended to include petunia.

Like PSTVd, TCDVd causes few symptoms in ornamental hosts.  Some puckering and distortion of the leaves and yellowing of the veins has been observed in infected plants, but these symptoms would seem to be temporary. However TCDVd can infect tomato crops, where it causes serious problems, with symptoms similar to those caused by PSTVd, such as stunting and yield loss.  There is a strong risk that TCDVd may also infect other important solanaceous crops such as peppers.  The major concern is that these infected ornamentals could act as a means for the dispersal of viroids, as its movement between ornamentals and the major hosts, by either mechanical or insect assisted transmission, cannot be ruled out. There is also a theoretical risk to potatoes from exposure to infected material, but this is extremely unlikely under normal (i.e. in the field) growing conditions.

Given the recent findings, growers of all solanaceous ornamentals should consider carefully the sourcing of all their propagation material, rooted cuttings, young and mature plants. Growers are strongly advised to seek assurances from their suppliers about the status of any material ordered and to have material already received tested for viroids before further propagation. Seeds of ornamentals should also be considered to be a potential source until proven otherwise.  However, propagation of cuttings from infected plants is considered to be the most likely route of infection.

Tomato and pepper growers are advised to avoid bringing solanaceous ornamental plants onto their nurseries. A helpful fact sheet on potato spindle tuber viroid is available from the  Horticultural Development Council (HDC). Given their close relationship, the advice given for PSTVd will also apply for TCDVd.

As part of an official survey, samples will be collected by Defra’s Plant Health and Seeds Inspectorate (PHSI) and sent for laboratory testing. PSTVd is an EU Annex IAI listed pathogen and TCDVd is absent from the EU and is considered to pose a significant risk to tomato crops; this means that any material found to be infected during the survey will be destroyed.