The invention is biodegradable chitosan-based foil, which is enriched with a potent antioxidant plant extract, obtained from an invasive plant species, Japanese knotweed (Polygonum cuspidatum, Fallopia japonica Houtt.), which due to its fast expansion poses global ecological damage, displaces autochthonous plants and leads to a reduction in biodiversity. Moreover, it is causing huge economic harm (e.g. damage to infrastructure).