The removal of moisture could act as a potential control strategy for smaller infestations of Japanese knotweed that scourge urban areas nationwide, a new study has found.

The research, carried out by NUI Galway in collaboration with infrastructure consulting firm AECOM and the University of Leeds, found that removing moisture has “a 100pc success rate” on killing and preventing the regrowth of the invasive alien plant which has the ability to grow through concrete.

The study concluded that while incorrect herbicide treatment “cannot control” the growth and regeneration of the species, fully drying the plant material in a lab environment allowed it to be returned to the soil without risk of regrowth. It also showed that, if there are no nodes attached to the underground shoots (known as ‘rhizome’), there is no regeneration.

Senior author of the study, Dr Karen Bacon, a lecturer in plant ecology, botany and plant sciences at NUI Galway, said: “Japanese knotweed is one of the most invasive plant species in the world and has major negative impact on ecology and biodiversity.

"The findings of this study showed virtually no difference between the regrowth of treated and untreated Japanese knotweed samples suggest that herbicide treatment, which is often the most suitable approach to tackle the species, is not always being done effectively.

“We also show clearly that the size of the plant fragment is critical to the initial regrowth, with smaller fragments producing much smaller regrown plants.

"Additionally, if there are no nodes, there is no regeneration, which may suggest potential management strategies in the future. This also highlights that small infestations and plants should not be viewed with the same concern as larger ones and that rapid management should be a goal of tackling this problematic species.”

She said the findings raise an important potential means of management for smaller infestations that are common in urban environments. 

Japanese knotweed can grow up to two to three metres 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.