Update on the situation of Ralstonia pseudosolanacearum in surface water in the Netherlands
In the Netherlands, Ralstonia pseudosolanacearum (EPPO A2 List) was first found in surface water in 2020 in the province of Utrecht, and in the province of Overijssel (EPPO RS 2021/179). In order to prevent any further spread of the bacteria with water, it is prohibited to use surface water to irrigate seed potatoes across the whole country. In areas where EU regulated Ralstonia species have been found in surface water, it is prohibited to use surface water to irrigate all types of potato crops. The NPPO of the Netherlands recently provided an update of the situation.
In September 2021 water samples were taken in the province of Overijssel and 8 samples tested positive for R. pseudosolanacearum. In November 2021 four plants of Solanum dulcamara, growing at the waterside in this area were sampled and all tested positive for R. pseudosolanacearum. In October 2021 water samples were taken in the province of Utrecht and 10 samples tested positive. In December 2021 seven plants of S. dulcamara were sampled and five tested positive. In both areas R. pseudosolanacearum survived during the winter period.
In 2022, water sampling started in June. In the province of Overijssel, samples tested positive in June, but in Utrecht the samples tested positive for the first time in July. In 2022, the survey for R. pseudosolanacearum was extended to other waterways in the Netherlands. In total 1305 water samples were collected at two times of the year. Twenty tested positive, including 5 samples from the existing irrigation prohibition area, and 15 samples from outside this area. These 15 samples were found upstream in the same waterway in Overijssel which already tested positive in 2020 and 2021. The irrigation prohibition area has been adjusted accordingly. The source of the infection is unclear.
The pest status of Ralstonia pseudosolanacearum in the Netherlands is officially declared as: Present: not widely distributed and under official control.
Sources
NPPO of the Netherlands (2023-07).
Vogelaar M, van de Bilt J, Blom N, Pel C, van Doorn B, Landman M, Gorkink P, Raaymakers T, Vreeburg RA, Bergsma-Vlami M (2023) Presence of Ralstonia pseudosolanacearum (phylotype I) in aquatic environments in the Netherlands. Plant Disease (early view). https://doi.org/10.1094/PDIS-11-22-2628-SC