A research study from the National University of Ireland (NUI) Galway has found that removal of moisture is 100% effective in killing Japanese knotweed, and its regrowth, under lab conditions.
This could act as a potential control strategy for smaller infestations of knotweed, which are common in urban settings.
The study, a collaboration between NUI Galway, University of Leeds and infrastructure consulting firm AECOM, found that incorrect herbicide treatment cannot control the growth and regeneration of this invasive plant but fully drying the plant material in a lab environment allowed it to be returned to the soil without risk of regrowth.
The research also showed that, if there are no nodes attached to the rhizomes – root-like underground shoots – there is no regeneration.
Japanese knotweed is a problematic invasive plant found in many areas of Europe and North America.
It can grow up to 2-3m in height and can dominate an area to the exclusion of most other plants.
Control of Japanese knotweed is complicated by its ability to regenerate from small fragments of plant material; however, there remains uncertainty about how much rhizome is required and how likely successful regeneration is under different scenarios.
The study, published recently in the journal, PeerJ, investigated the ability of crowns (underground mass from which rhizomes and shoots emerge) and rhizomes with different numbers of nodes to regenerate successfully from three sites in Yorkshire and Lancashire in the north of England.
Two of the sites had been subject to herbicide treatment for two years prior to sampling and the third site had no history of herbicide treatment.
The study found that the success of regeneration is related to plant fragment size, with larger fragments more likely to successfully regenerate and, for rhizomes, if there is no node, there is no regeneration.
Additionally, it was found that the removal of moisture on living material resulted in 0% regeneration after plant material was dried and replanted.