First report of Gymnocoronis spilanthoides in the Netherlands
Gymnocoronis spilanthoides (Asteraceae: EPPO A2 List) is a well-known plant in western Europe where it is appreciated for its easy vigorous growth as an aquarium plant, or for its striking fragrant flowers as a pond plant. Native to South America, G. spilanthoides is an invasive alien species in Australia, New Zealand, Japan, China and Taiwan. Within the EPPO region, G. spilanthoides has been recorded in Hungary in canals connected to thermally influenced waters and in a canal in Italy (north-western Lombardy region). In the Netherlands, an unknown aquatic plant species was reported in the urban waterway in Vleuten in 2019 via mobile applications. This triggered a verification action by the NPPO in the Netherlands in accordance with the established early warning protocol for invasive alien species. On September 2019, the identity of the species was confirmed on site (coll. Valkenburg 4038 (L, WAGPD), Vleuten, 20 IX 2019) and the size and extent of the infestation assessed. Based on the size and distribution of the plants along the waterway as well as Google street view images from 2018 (where the invaded population could be clearly seen due to the distinctive green colour of the foliage compared to the Phragmites species in the area) it was concluded that G. spilanthoides has been present at this site for several years, and can survive under the Dutch climate. Eradication measures have been taken. This included washing the root system and using a mesh to filter and retain the root fragments to avoid contamination of the water, along with the subsequent removal of plant material to a certified composting facility. The site will be monitored over the coming years to control any regrowth.
NPPO of the Netherlands (2020-03).