Smalle theeplant (Gymnocoronis spilanthoides (D. Don ex Hook. & Arn.) DC., Asteraceae), een onverwachte eerste vondst voor Nederland

Senegal Tea (Gymnocoronis spilanthoides (D. Don ex Hook. & Arn.) DC., Asteraceae) is a well-known plant for aquarists in western Europe. Appreciated for its easy and vigorous growth as an aquarium plant or for its striking fragrant flowers as a pond plant. Since August 15, 2019, the species is included in the list of invasive alien species of Union concern pursuant to EU regulation no.1143 / 2014. Whereas an array of alien aquatic plants, such as Water Lettuce (Pistia stratiotes L.), Water Hyacinth (Eichhornia crassipes (Mart.) Solms), Giant Salvinia (Salvinia molesta Mitch.), Parrot’s Feather (Myriophyllum aquaticum (Vell.) Verdc.), and Fanwort (Cabomba caroliniana A.Gray), can be commonly found in urban waterways in the Netherlands, escapes of Senegal tea were unknown. This has changed in autumn 2019. Senegal Tea is native to South America and has recently become a problematic species in other continents. It is considered an invasive alien species in Australia, New Zealand, Japan, mainland China, and Taiwan. In Europe, the species has recently established in Lombardia in Italy. The plant was first recorded in the Netherlands along a watercourse in Vleuten, Province of Utrecht, on August 30, 2019, by a volunteer who reported this as a species unknown to him in the app NOVA. In early September, the plant was recorded at the same locality twice and its identity was confirmed in another recording app. This triggered a verification action by the NVWA (Netherlands Food and Consumer Product Safety Authority) in accordance with the early warning protocol in place for IAS (Invasive Alien Species) in the Netherlands. On September 20, the identity of the species was confirmed on site (Valkenburg 4038 (L, WAGPD), Vleuten, 20 IX 2019) and the actual size and extent of the infestation delimited. Based on the size and distribution of the plants along the watercourse as well as the presence of a clump of Senegal Tea plants on Google Street View images made in 2018, it is clear that the species has been at the site in Vleuten for several years. Hence it can be considered hardy in the Netherlands. Eradication measures have been taken, comprising containment of the individual plants by metal mesh of 5 mm prior to washing out the root system and subsequent removal of plant material to a certified composting facility. The site will be monitored for the coming years to control any regrowth that may sprout.