Parkslide i Sverige. Bekämpningsmetoder och deras effektivitet

Abstract

Invasive Alien Species (IAS) are an increasing concern in a globalized world where more species are transported and planted beyond their native environments. Japanese knotweed (Reynoutria japonica) is notoriously difficult to eradicate and has negative effects on environment and society. Methods are continuously developed, suitable for various sites and conditions. This study investigated which eradication methods are currently used in Sweden, their efficacy, and how soil levels of glyphosate, an herbicide used for eradication, and its metabolite AMPA change over time. New measurements of Japanese knotweed communities previously treated, with three different glyphosate methods or by coverage, in a pilot study by Göteborgs Stad (2021) showed a significant reduction in community size. This demonstrates an effect of all methods in the pilot. To evaluate glyphosate’s persistence in soil, results from the pilot 2021, where soil samples were collected before and 48 hours after treatment, where compared to new follow up samples from the same location. The results revealed that glyphosate had declined below detectable levels, while AMPA concentrations had increased over time. This indicates that when glyphosate is degraded, AMPA accumulates in the soil, and that AMPA appears to have a longer degradation time than glyphosate. Through a questionnaire study with professionals in the field, coverage was found to be the widest used eradication method. However, several other methods were perceived as more effective. The discrepancy likely relates to these methods being newly developed and not widely known, with limited evidence of their long-term efficacy. As most eradication efforts have occurred between 2020 and 2025, these results should be considered preliminary. Continued monitoring is needed to assess long-term efficacy of different methods. Eradication of Japanese knotweed is complex, and many factors need to be considered. No method is effective in every case, rather, a toolbox of varied methods is needed to eradicate the species in the environments in which it grows.