What drives the success of knotweed control by tarping?

Faced with increasingly constraining herbicide regulations, many land-managers are turning towards alternative methods to control highly invasive plants. For clonal plants such as Japanese knotweed s.l. (Reynoutria spp.), “tarping” (a.k.a. covering) is frequently applied yet with contrasting results, as robust recommendations regarding effective application are currently lacking. We used a survey-based dataset of tarping operations in Europe and North America to explore the factors affecting the success of knotweed control by tarping. Variations of four response variables were analysed: an effectiveness score (estimating the capacity of tarping to limit the vigour, lateral spread and propagule dispersal of knotweed stands), the visual eradication status of the plant, and the presence of knotweed regrowth at the edge of the tarped area or at the junction of fabric strips. Among 85 evaluated operations, 59