My Department has worked closely over the years with the Northern Ireland Environment Agency (NIEA) to fund and manage the Invasive Species Ireland Project and this initiative resulted in Best Practice Management Guidelines for a number of invasive species, including Japanese knotweed being published on the project website at www.invasivespeciesireland.com.
However, the Best Practice Management Guidelines for Japanese knotweed were removed from the Invasive Species Ireland website as there is now a requirement to review and update these guidelines. Work on this review and the development of updated guidelines is currently underway.
In the meantime, information on general management approaches to invasive plant species is available from the Invasive Species Ireland website:
http://invasivespeciesireland.com/toolkit/invasive-plant-management/