Four outbreaks of Columnea latent viroid (CLVd) have been confirmed at tomato production nurseries in England. These are the first outbreaks of this viroid in the UK.

CLVd is closely related to Potato spindle tuber viroid (PSTVd) and Tomato chlorotic dwarf viroid (TCDVd). PSTVd was confirmed in 2003 at a tomato production nursery in the UK and more recently both PSTVd and TCDVd have been found in Solanaceous ornamentals.

The primary natural hosts of CLVd are tomatoes and ornamentals (Brunfelsia undulata (Jamaican raintree), Columnea erythrophae, Nematanthus wettsteini (goldfish plant).Like PSTVd and TCDVd, CLVd causes few symptoms in ornamental hosts. However CLVd causes serious problems in tomato. Symptoms can be similar to those cause by PSTVd, with stunting, leaf distortion and chlorosis. However, in the UK outbreaks leaf reddening ('bronzing') and necrosis were also prominent symptoms. Potatoes are  a potential host and there is a theoretical risk to potatoes from exposure to infected material, but this is extremely unlikely under normal growing conditions.

Statutory controls have been put in place on the affected nurseries requiring hygiene measure, to prevent further spread, and restriction on the marketing of the fruit. Investigations are underway to establish the extent of infection, links to other sites and how it got onto the nursery.

Long distance spread of CLVd is most likely by infected plants or possibly by  infected seed, although seed transmission is not yet proven. Once CLVd has been introduced onto a farm or nursery, it can be spread from plant-to-plant by mechanical means, through the use of contaminated cutting tools, on machinery, by handling or simply by direct plant-to-plant contact. The best means of controlling CLVd is by planting pathogen-free plants or (possibly) pathogen-free seed .

Tomato growers are advised to inspect their crops and report any suspicious symptoms to their local Plant Health and Seeds Inspectorate (PHSI). CLVd is absent from the UK and is considered to pose a significant risk to tomato crops; this means that any material found to be infected would be subject to statutory controls.

A helpful fact sheet (09/06: Potato spindle tuber viroid in tomato and new viroid reports) is available from the Horticultural Development Council (HDC). This includes some information about CLVd and given their close relationship, the advice given for PSTVd will also apply for CLVd.