This report contains the result of a research project on four invasive aquatic macrophytes, Cabomba caroliniana (Fanwort), Hydrocotyle ranunculoides (Floating pennywort) , Myriophyllum aquaticum (Parrott’s feather) and Ludwigia grandiflora (Water primrose). The collaborative project was intended to generate a prototype decision support system for optimising control measures for these species, considered to be the four most troublesome invasive alien aquatic weeds at present in the UK and NL. A further reason for selecting these species is that they are widely sold in the horticultural trade and are therefore the number of invaded sites is likely to increase in the short term.