For the past few weeks, Invasive Weeds Agency Ltd has been undertaking a control programme of Japanese knotweed near Castle Douglas in the South-West of Scotland using stem injection in what appears to be the largest project of this kind in the country.
The stem injection method involves using a device similar to a syringe in order to inject the herbicide directly into the stem of Japanese knotweed. This method is very effective at controlling Japanese knotweed, however, it is more labour intensive than herbicide spraying. Also, there are areas where it is not appropriate to use stem injection due to health and safety risks to the operator, such as when working close the water’s edge or on a very steep slope. Stem injection is of particular value when Japanese knotweed is growing amongst more desirable plants where there is a risk that herbicide spraying may have a negative impact on the plants surrounding the Japanese knotweed. The stem injection method is also useful as a follow-up to herbicide spray treatment of large areas in order to tackle any plants missed or ones that have not been affected by the spray treatment.
We will not be replacing herbicide spraying with stem injection as we believe that it is important to assess the best method for every individual site. Stem injection is useful for some sites and not for others, as is the case for spraying, digging etc.
IWA. Getting to the root of the problem.