A new mechanical method for the control of japanese knotweed successfully proved on the Ain and Isère rivers

Abstract

The recent development of powerful portable machinery for the consolidation of soil on development sites, provides new opportunities for the mechanical treatment of Japanese Knotweed, by mechanical actions directly made on the rhizomes, the only perennial organ of the plant. Further to the success of the first experiment in 2005/2006 on the river Ain, a new experiment had been tried in 2007/2008 on the Isère river and it was a success too. With extremely drastic precautions to avoid the spreading of the knotweed by the worked machines, this method can be used without a complex setting up. Moreover, a direct immersion test of overrun soils in a pond during winter showed with certainty that the site was contaminated. Today, this solution which is envisaged by different river authorities to manage digged alluvia, shows considerable ecological risks for the ponds, and it requires significant precautions to avoid a bank colonization by the invasive plants.