New Zealand pygmy weed - update

The following are brief summaries of some of the action that we and our partners have done since the Species Action Framework was launched. They're in chronological order, with the most recent updates at the top of the page.

December 2010

Control of New Zealand pygmyweed at Mochrum Lochs SSSI - year 4. In Mochrum Loch, spot herbicide treatments of small areas of colonisation by New Zealand pygmyweed were carried out in March 2010. Larger areas of habitat supporting the species were again covered with weed control fabric. When Mochrum Loch was surveyed in September 2010, it was found that the cover of habitat by New Zealand pygmyweed had decreased from 516 to 268 square metres and there were no large areas of colonisation. However, New Zealand pygmyweed was found occupying small areas throughout the habitat. The majority of these areas were likely to have been colonised recently. Although there had been an overall reduction in cover by New Zealand pygmyweed, of 97% since management began, presence of these newly colonised areas represents a threat to the condition of the Loch. It is therefore necessary that management continues.

December 2009

Control of New Zealand pygmyweed at Mochrum Lochs SSSI - year 3. The remaining weed control fabric was removed in March 2009. It appeared to have had a considerable effect in the areas in which it was employed. No evidence of viable New Zealand pygmyweed was found in areas that had been covered, except where the plant had escaped between overlapping sheets of fabric. New Zealand pygmyweed was found to cover approximately 359 square metres of habitat at Mochrum Loch. Significant control of the species had therefore been achieved, representing a 96% reduction in the New Zealand pygmyweed growing at the Loch.

Following removal of the weed control fabric, targeted spot herbicide treatments were undertaken on the remaining New Zealand pygmyweed. Glyphosate was applied to the edge/emergent plants and dichlobenil to the submerged plants.

The three lochs of the SSSI were again surveyed in September 2009. Castle Loch and Black Loch remained free from New Zealand pygmyweed. In Mochrum Loch, there had been a small increase in cover since March, but the control measures had nevertheless resulted in a decrease in cover by New Zealand pygmyweed, of approximately 95% since 2007, and the main large areas of infestation had been removed.

December 2008

Control of New Zealand pygmyweed at Mochrum Lochs SSSI - year 2. In spring 2008, weed control fabric was deployed to shade the New Zealand pygmyweed. This was left in place for several months. A proportion of the weed control fabric was removed in December 2008.

May 2008

Assessment of risk from existing populations of New Zealand pygmyweed - On behalf of Scottish Natural Heritage, the University of Stirling collated information on the current distribution of New Zealand pygmyweed in Scotland. For each population, the source and means of colonisation was assessed. The risk posed by each population, in terms of potential for spread, and in situ and regional threat to protected sites or species, was then categorised. The categorisation took into account the use of the site, its accessibility, size and origin, and the connections to other sites. The information provided by this project will be the basis for prioritising work on control/eradication of populations of New Zealand pygmyweed. A report is available here.

April 2008

Training manual for identification of invasive non-native species - A training manual has been prepared to raise awareness of New Zealand pygmyweed and other invasive non-native aquatic plants. In addition to New Zealand pygmyweed, there are other invasive non-native plants associated with freshwater that also threaten Scotland's biodiversity, and the Species Action Framework action for New Zealand pygmyweed is being used to highlight the wider management issues associated with the invasive species covered in the training manual.

The training manual is in two parts - an Identification guide    and a Powerpoint presentation  .

December 2007

Control of New Zealand pygmyweed at Mochrum Lochs SSSI -  year 1. In 2004, New Zealand pygmyweed was recorded in Mochrum Loch during Site Condition Monitoring at Mochrum Lochs SSSI. In September 2007, a detailed survey of the distribution and abundance of New Zealand pygmyweed in Mochrum Loch was undertaken by a contractor, ECUS Ltd.. The other two lochs of the SSSI and surrounding wetland habitats were also surveyed at that time and appeared to be free from colonisation by this species. In September 2007, the coverage of habitat at Mochrum Loch by New Zealand pygmyweed was estimated as 1 hectare (10,000 square metres).