Cabomba caroliniana (Fanwort) in The Netherlands 3rd International Symposium on Weeds and Invasive Plants Johan van Valkenburg, Rudi Roijackers & Rosalie Léonard The species involved • A common component of your Goldfish plant selection 2 Cabomba caroliniana | October 2011 Cabomba caroliniana or Cabomba aquatica ? • In trade Cabomba aquatica is often misapplied to C. caroliniana plants C. aquatica C. caroliniana Flowers Yellow White Submerse 3-dimensional Mostly 2- leaves dimensional Emerse Round Elliptic leaves 3 Cabomba caroliniana | October 2011 Cabomba caroliniana distribution 2010 Published sources 4 Cabomba caroliniana | October 2011 A brief history for The Netherlands • First record 1989 Maasbracht (Meuse River) NOT invasive • Since 2005 at Loosdrecht INVASIVE • Spring 2006 first attempt at eradication • Summer 2007 Oranje channel near Orvelte expanding • Summer 2008 suburban area at Hoogeveen & fish pond Groningen • Summer 2010 suburban area Hardinxveld, Ridderkerk, Barendrecht • Summer 2011 suburban area Heerenveen 5 Cabomba caroliniana | October 2011 What to do ? • Identification tools & training of field staff • Research on habitat requirements • Research on genetic diversity • Research on management options 6 Cabomba caroliniana | October 2011 Identification tools • Field guide • Info sheet 7 Cabomba caroliniana | October 2011 Habitat requirements Survey March, July, October 2008 Visit at the 3-4 known localities Results: • Wide tolerance for nutrient levels • Large range in conductivity level • Floating plants limit growth • Competition with Myriophyllum heterophyllum Conclusions: • Site conditions do not explain difference in invasive behaviour • Can grow in any eutrophic stagnant to slow flowing water with a sediment poor to very rich in organic matter 8 Cabomba caroliniana | October 2011 Genetic diversity • In collaboration with Plant Research International and CSIRO • Sampling of all known localities in NL • Additional samples invasive populations in France, Germany and Australia • Samples from import shipments SE Asia 9 Cabomba caroliniana | October 2011 Management options EUPHRESCO DeCLAIM project Funding: UK Defra and NL LNV Partners: • Plant Protection Service NL • Wageningen University & Research • CEH - Wallingford Target species: • Cabomba caroliniana • Hydrocotyle ranunculoides • Ludwigia grandiflora • Myriophyllum aquaticum 10 Cabomba caroliniana | October 2011 EUPHRESCO Cabomba trials at Loosdrecht 11 Cabomba caroliniana | October 2011 Cabomba management Field testing 4 methods at Loosdrecht • Standard practice • Washing out • Covering surface • Covering bottom CHARISMA model to assist DSS • Detailed measurements in time • Predicting competition • Timing of management actions 12 Cabomba caroliniana | October 2011 Trial lay out • Standard 3 X 100 m & enclosures • Washing 3 X 100 m & enclosures • Surface coverage 2 X 100 m • Bottom coverage 10 X 10 m • Scheduled for early April performed by May 20th (standard) and July 14th (washing) 13 Cabomba caroliniana | October 2011 Location map trials Loosdrecht 14 Cabomba caroliniana | October 2011 Standard practice J M u a n y e D e c J e u m l b e y r 15 Cabomba caroliniana | October 2011 Result of standard practice • After 1 year dominance Cabomba just like it was before management (June 75-90%; August 80-90%) Enclosures (1 x 1 m) • On average 9(3-30) stems of Cabomba present • Elodea nuttallii July 15-40 % coverage August 40-100% coverage Dominance Cabomba resulting from regrowth, inflow of fragments and competitive advantage grazing 16 Cabomba caroliniana | October 2011 Washing out with hydro-venturi system 17 Cabomba caroliniana | October 2011 Result of washing out • After 1 year dominance Cabomba still reduced (June 5-10%; August 25-50%) Enclosures (1 x 1 m) • Just 1 cage with a few stems of Cabomba entering from the side • Elodea nuttallii coverage August 25-100% coverage Recovery of Cabomba resulting most likely from inflow of fragments and competitive advantage grazing 18 Cabomba caroliniana | October 2011 June 2010 enclosure with Cabomba 19 Cabomba caroliniana | October 2011 June 2010 outside enclosure 20 Cabomba caroliniana | October 2011 August 2010 Elodea nuttallii (other enclosure) 21 Cabomba caroliniana | October 2011 Coverage with black woven geotextile Coverage of sediment Coverage of surface • Recolonisation of Cabomba on new • No plant growth in July sedimentation on top of fabric • No plant growth after 1 month partial removal of fabric Does not work in a situation with siltation and large quantities of August 2011 propagules in the vicinity • 1st ‘removed’ stretch 2 Cabomba stems & 5 plants M. verticillatum 50% cover • 2nd ‘removed’ stretch No Cabomba & 7 plants M. verticillatum 50% cover M. verticillatum and U. vulgaris on top of fabric Non discriminant effective method 22 Cabomba caroliniana | October 2011 Surface coverage experiment August 2010 23 Cabomba caroliniana | October 2011 Surface coverage experiment August 2011 24 Cabomba caroliniana | October 2011 CHARISMA model • Determine growth parameters • Life-cycle knowledge • Vulnerable stages in development • Energy allocation • First findings 25 Cabomba caroliniana | October 2011 Charisma ‘conclusions’ Predictions on growth and competition do not match field observations • Growth potential underestimated • Critical role of root system • Photosynthesis parameters to be evaluated April 2011 26 Cabomba caroliniana | October 2011 Conclusions • Standard practice will not eradicate Fanwort in eutrophic waters • Yearly cleaning in autumn has resulted in 100% dominance of Fanwort in ditches • Washing out is a quite effective method to remove macrophytes rooting in the sediment (e.g. Cabomba & M. heterophyllum) • There is no ‘best management ‘ option • Solution has to be adapted to the actual site conditions: Dimensions of the waterway Conditions of the bank Function of the waterway 27 Cabomba caroliniana | October 2011.