BuRO advice on the risks of four Asian knotweeds in the Netherlands

Examples of measures are:

stopping the trade in Japanese knotweed (including Fallopia japonica var. compacta), giant knotweed, Bohemian knotweed and Himalayan knotweed. including viable partseld of soil transport, garden waste, organic waste, compost and the trade in stems;

measures in the field of soil transport, garden waste, organic waste, compost and the trade in stems.

BuRO also provides the Minister of LNV with the following advice:

• Take measures to prevent hybridization and generative reproduction by seed formation, for example by stimulating the detection and removal of male specimens of Japanese knotweed, giant knotweed and Bohemian knotweed.
• Consider setting up the measures in such a way that they also apply to species that cannot or can hardly be distinguished visually from the aforementioned species, unless it has been convincingly demonstrated that these subspecies or hybrids do not pose any risks to Dutch nature or other social values.
• Submit the Japanese knotweed, the Sakhalin knotweed and the hybrid knotweed to the European Commission for inclusion on the European Union list of invasive alien species of Union concern.

Asian knotweed

Japanese knotweed, giant knotweed and Bohemian knotweed have settled in the Netherlands and are widespread in both urban and natural areas. These species form dense settlements, displacing native plant species, reducing the presence of invertebrates and changing ecosystems. Since 2012 it is known that in the Netherlands there are male plants which can fertilize females specimens of Japanese knotweed. The Dutch climate currently seems suitable for the successful setting and maturation of seeds seed of Japanese knotweed, giant knotweed and Bohemian knotweed. If viable seeds are formed, they can easily be spread by water and wind.

Background

Due to the spread in the Netherlands of Japanese knotweed, giant knotweed and Bohemian knotweed, the problems experienced in removing the species and the discovery of Japanese knotweed with seeds, the Office for Risk assessment & Research (BuRO) of the Netherlands Food and Consumer Product Safety Authority (NVWA) has asked the question what risks the species pose for biodiversity, ecosystem services and other social values.