Action: Crassula helmsii: Physical control using manual/mechanical control or dredging
- We found no evidence for the effects of physical control, using manual or mechanical control or dredging, on Crassula helmsii.
'No evidence' for an action means we have not yet found any studies that directly and quantitatively tested this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.
Mechanical control could be used to remove Crassula helmsii from affected waterways, either by removing vegetation using mechanical or manual methods, or by dredging entire waterbodies. This approach may reduce the dominance of the plant, but is often not fully effective. This is because of the difficulty of removing all the vegetation without small sections breaking off, in combination with C. helmsii’s ability to regenerate from any small fragments that remain (Dawson & Warman 1987). It may require drainage of a pond and removal of the top layer of soil to completely eradicate C. helmsii (Leach & Dawson 2000). The intervention ‘Surround with wire mesh’ discusses using mesh to surround treatment sites and minimize spread of disturbed plant fragments. Dredging and re-profiling waterbodies are included in the intervention ‘Alter environmental conditions to control plants’, and other physical approaches to removal of C. helmsii are discussed in ‘Drying-out waterbodies’ and ‘Burying plants’.
Dawson F. H. & Warman E.A. (1987) Crassula helmsii (T. Kirk) Cockayne: Is it an aggressive alien aquatic plant in Britain? Biological Conservation, 42, 247-272.
Leach J. & Dawson H. (2000) Is resistance futile? The battle against Crassula helmsii. Journal of Practical Ecology and Conservation, 4, 7-17.