Control of Myriophyllum verticillatum L. in Irish canals by turion removal

Abstract

Myriophyllum verticillatum L. is the single most obstructive aquatic plant in Irish canals. Because of the importance of these canals as national amenities, considerable resource has been directed towards the long-term control of this aggressive plant. A combination of mechanical harvesting and chemical treatment has traditionally been employed to control Myriophyllum growth but these methods have only provided short-term control. Myriophyllum verticillatum reproduces by producing turions between September and November each year. These over-wintering propagules sink to the canal bed where they remain dormant until February. At a trial site on the Royal Canal turions were harvested in November 1994 and 1995, significantly reducing the number of propagules present. Biomass and plant cover with M. verticillatum throughout the 1995 and subsequent growing seasons was dramatically reduced. The implications for weed control programmes, habitat development and amenity usage are discussed.