The Management of Giant Hogweed in an Irish River Catchment

• Published in: Journal of aquatic plant management 2001-01, Vol.39, p.28-33
• Main Author: Caferey, J M
• Format: Article
• Language: English
• Subjects: Eire; Freshwater; Heracleum mantegazzianum
• ISSN: 0146-6623

Giant hogweed (Heracleum mantegazzianum Sommier and Levier) is an alien plant that was introduced to Ireland as an ornamental in the late 19th Century. The banksides of rivers and streams are the preferred habitat for the plant and it is now a feature in many important angling catchments. The continued spread of this plant is a cause of concern because of its impact on human health and on the ecology of infested river corridors. As giant hogweed populations can only be perpetuated by seeds, most control strategies aim to limit recruitment to future generations and to deplete the seed bank reserve. Trials conducted in Ireland and in Europe have revealed the sensitivity of the plant to herbicidal treatment using glyphosate. Based on research conducted in Ireland a four-year treatment program, using glyphosate, was formulated. Prior to 1998 no coordinated attempt to eradicate giant hogweed from a catchment had been undertaken. To investigate the feasibility, and logistics, of managing this hazardous plant in a discrete river catchment, a control program on the Mulkear River catchment (670 km super(2)) was undertaken by the Office of Public Works. Field surveys indicated that an area of circa 35 km super(2) within the catchment was overgrown with giant hogweed. Weed treatment commenced in March 1998 and continued through 1999 and 2000. With almost three of the four-year treatment schedule complete, the preliminary results are very encouraging. The benefits to the local community and the overall ecology of the river and riparian habitats are discussed.