Further details on earlier findings of Ralstonia solanacearum biovar 2 race 3 in Pelargonium zonale cuttings in Europe
Relatively recent findings of R. solanacearum biovar 2 race 3 on Pelargonium, both in Europe and USA, raised the problem of its possible spread to potato crops (see EPPO RS 2001/106, 2001/124, 2003/064). A paper from Janse et al. (2004) gives details about the findings which have been made in Europe in 1999/2000. They recalled that in December 1999, a sample of imported cuttings of Pelargonium zonale was found infected by Ralstonia solanacearum (EPPO A2 list) in United Kingdom. From September to December 2000, symptoms of bacterial wilt were observed in several Pelargonium nurseries in Belgium and Germany. R. solanacearum biovar 2 race 3 was consistently isolated and identified. Latent infections were detected also in the Netherlands on imported material. Surveys carried out in these countries showed that the origin of the infection was cuttings produced in Kenya by several nurseries for export to associated companies in Belgium, Germany, Netherlands and UK for further propagation.
In Kenya, it was found that contamination of nurseries was probably due to the use of contaminated water (river) for irrigation. The water may have become contaminated from infected potato crops known to be situated upstream. In the nurseries concerned, infected plants usually showed symptoms, and the number of latently infected plants was low. At the beginning of 2001, all mother material and cuttings from infected Kenyan nurseries were checked and all infected or suspect material was destroyed. Glasshouses and equipments were disinfected. Irrigation water was no longer taken from the river, but was either taken from a well or disinfected.
In Europe, the following phytosanitary measures were taken:
- destruction of all plants of infected cultivars by burning or deep burial;
- disinfection of infected glasshouses, machines, tools etc.
- officially controlled delivery of all potentially infected lots, after testing, to local market only;
- tracing of all nurseries receiving material from Kenya;
- sampling and testing of all Pelargonium plants on contaminated nurseries and nurseries receiving propagating material from Kenya;
- prohibition to use surface water for irrigation not only for potato and tomato, but also for Pelargonium, Portulaca oleracea (demonstrated as being a host), Solanum melongena and S. sisymbriifolium in known contaminated surface water areas.
In 2001/2002, visual inspection and testing for latent infections were done in Europe and Kenya and no further infections were found on Pelargonium.
Janse, J.D.; van den Beld, H.E.; Elphinstone, J.; Simpkins, S.; Tjou-Tam-Sin, N.N.A.; van Vaerenbergh, J. (2004) Introduction to Europe of Ralstonia solanacearum biovar 2 race 3 in Pelargonium zonale cuttings.
Journal of Plant Pathology, 86(2), 147-145.