Japanese knotweed is extremely hardy and should really only be tackled and disposed of by an expert, especially if you want to be sure you have eradicated every last trace of it. DIY attempts to burn knotweed away or even treat it with bleach, as some people have tried, will be futile as it will continually keep growing back.
So, how do you kill Japanese knotweed? Here are a few known knotweed treatments offered by JKSL:
1) Knotweed herbicide treatments
Current control methods rely mainly on chemicals. Herbicides, such as glyphosate based products, can be used in spray form on the foliage, but only in areas that are not ecologically sensitive.
Depending on the herbicide applied, late Summer/early Autumn is the most effective time to chemically spray Japanese knotweed as this is when the plant is in full leaf. By spraying onto the foliage just before the plant goes into senescence, will ensure that the herbicides effectively make their way to the root system.
In areas where spraying is not suitable and herbicides need to be used sparingly, stem injection methods can be used, whereby injecting the chemicals directly into the stem of the plants.
Herbicide treatments take time to work, with chemical treatments taking around 3 to 5 years to complete.
2) Knotweed excavation
The only way to be absolutely certain of permanently removing the Japanese knotweed is to professionally dig out the underground roots with machinery. The extensive network of rhizomes need to be carefully removed so as to ensure that no small fragments remain which could re-grow.
The excavated rhizome and soil would need to disposed of at a licenced landfill facility or an alternative plan for on-site burial (such as inside a heat-sealed geo fabric membrane).
3) MeshTech treatment of knotweed
In today’s more environmentally aware days, the use of herbicides is increasingly frowned upon as a solution to getting rid of Japanese knotweed. MeshTech provides a more eco-friendly alternative as it does not involve the use of any chemicals.
The new technique uses the knotweed’s aggressive nature against itself by forcing the plant to sever its own stems on a mesh placed over it where it grows. This method was designed by Dr Eric Connelly and JKSL, and has minimal impact on the surrounding environment, meaning it is an ideal deal technique for use on riverside locations, railway embankments and highways.
4) Biological control of knotweed
Another eco-friendly method includes the use of biological control in the form of releasing natural predators, such as the psyllids insect, which although it will not kill Japanese knotweed, may help naturally keep it under control.
Research has identified the psyllid, an insect naturally found in Japan, as safe for introduction to control Japanese knotweed in the UK. Several years of research in Japan and in quarantine facilities in the UK identified the insect as effective at controlling knotweed as well as the impact on native plants and invertebrates being low. The insects have been released around riverways where they were more likely to thrive and further research is continuing into the effectiveness.