The regional board of Freibug / Germany has finished its research on the control of Japanese knotweed with mere hot steam without chemicals which was started in autumn last year. The last treatment process was conducted to distroy the plant’s rhizomes in deep soil layers.
Already in september 2009 the experiment with hot steam was started. Large areas on the shore of the river Rench which were highly contaminated with Japanese knotweed were excavated down to 20-30 cm depth and steamed completely. The success oft he treatment of more than 95% was already visible at the end of the year 20009 and even more at the beginning of 2010. On the treated area only scattered sprouts appeared as expected.
Counter measures against these sprouts were taken by depth treatment with steam. High pressure lances made by the company MTM-SPINDLER were first driven into the soil down to about 1 m depth. The soil was broken and loosened with induced highly compressed air. Then steaming lances were applied and host steam at 200°C induced for about 15 min.
Already in May 2009 a similar test was made together with a regional government organization in the southwest of Germany to sucessfully kill all surviving germinable root residues after a first superficial treatment of contaminated area.
Hot steam denatures all germinable plant parts in the soil and harms them sufficiently that invading germs weakens the plants to a degree that no offspring can be produced.
Later on the positive results will be further supervised and checked if there is a sustaining positive effect.