Techniques for controlling Crassula helmsii in United Kingdom
In the United Kingdom, Crassula helmsii (Crassulaceae - EPPO Alert list) is a highly invasive aquatic plant out competing many native plants by forming dense smothering mats of vegetation.
In 2003, action was needed to control or eradicate the plant in Old More (near Barnsley, South of Leeds), where the plant had probably been present for about 10 years.
- Smothering and burying: in March 2003, black plastic was laid over areas of Crassula and topped with about a metre of soil. Although a 100% kill was achieved, this is not a feasible method to employ on such a large site, as it is very labour-intensive and causes much disturbance.
- Spraying biodegradable “Waipuna” hot foam: Waipuna is a biodegradable organic compound of coconut and corn sugar. Applied as hot foam, the solution holds in the heat to break down the cellular structure of the plant. Spread 3 times about one month apart in September, October and November, the hot foam produced a 50% kill rate. The treatment was stopping the spread of the plant rather than eradicating it.
- Spraying with Glyphos biactive: Exposed C. helmsii was sprayed in July and August 2004 with Glyphos Biactive at 5 l/ha. The results were similar to those from spraying with “Waipuna”, with an approximate kill of 50% over areas where it was applied.
Bridge T (2005) Techniques for controlling New Zealand Pygmyweed. British Wildlife, October, 19.