NL: No further spread of Ralstonia in cut roses

In 2015, 13 companies (9 growers of cut roses and 4 plant growers/breeders) were contaminated with the brown rot bacterium Ralstonia solanacearum. It is of utmost importance to prevent the further spread of the disease within the company and within the horticultural sector. By the end of 2015 NVWA decided, as a precaution, to extend the investigation to all growers of cut roses. In January/February 2016 no further spread of contaminated companies was noted.

The first contaminated companies are in the meantime almost all cleared, cleaned and disinfected after which they started a new crop. In the coming period these companies will be monitored by NVWA.

Race 1 of the brown rot bacterium was detected. Race 1 is mostly restricted to tropical environments and has a wide range of host plants among which are tomato, pepper, eggplant, Anthurium, Gerbera, Curcuma, Geranium and rose. This tropical race likes warm temperatures; only after the summer will we be able to draw conclusions. Together we will be working on eradicating this disease from the Dutch rose growers and breeders.

A genetic comparative analysis
As mentioned previously the genetic comparative analysis showed that there is no relation between the contamination in roses and the earlier found contamination in tomatoes, Curcuma and Anthurium. The inspected contaminations in roses however are related. Currently all isolates from the samples of contaminated roses and water are further examined. It takes into account that the DNA-profiles are compared between themselves and with worldwide databases of DNA-profiles of Ralstonia. Possibly this will lead to clues as to where this Ralstonia originated from geographically. Sadly the source is not known yet. In brainstorm sessions with growers, propagators, Naktuinbouw and NVWA various possibilities were raised. These will be investigated by NVWA.

The Action Plan: chain approach eradicating Ralstonia
The national commission of Roses of LTO Glaskracht Nederland in due consultation with Plantum drafted an Action Plan to ensure that new outbreaks of Ralstonia does not arise in the future. Work is also underway in conjunction with the government, inspection services and knowledge partners on a research project PPS Ralstonia to answer the many remaining questions as soon as possible.

Advisory map Ralstonia solanacearum
There are no known pesticides against Ralstonia. Another is that it concerns a q-organism and the plants contaminated with this bacterium must be destroyed according to the EU-Fytorichtlijn 2000/29/EG. With finances from the Productschap Tuinbouw an advisory map has been developed by Groen Agro Control in collaboration with LTO Glaskracht. A paper version of the advisory map is available on request from LTO Glaskracht Nederland.

Source: LTO Glaskracht Nederland