All Rhodies lead to Galloway

I was delighted today to learn I've been awarded a contract to carry out a survey for the non-native invasive shrub Rhododendron ponticum at several sites in Galloway. In England, ponticum is listed in Part II Schedule 9 of the Wildlife and Countryside Act 1981 (and amendments) which makes it an offence to plant or allow it to grow in the wild, and landowners have a duty to remove it if it occurs on their property. The situation is different in Scotland. Ponticum is listed in the Scottish Biodiversity Strategy’s Species Action Framework (SAF) as an invasive non-native species that presents a great risk to biodiversity – but it is not a Schedule 9 species north of the border and there's no compulsion on landowners to act.

Nevertheless, responsible land owners appreciate they have a duty of care to the environment. Ponticum is widespread and abundant in woodlands throughout Scotland, where it has led to a serious decline in the abundance and diversity of the associated native plant communities. It spreads rapidly and regenerates from small fragments of material. It is poisonous to livestock and cannot be controlled by grazing. It is host to the disease organisms Phytophthora ramorum and P. kernoviae, which attack oak and beech. In 2011, hundreds of Japanese larch trees had to be felled at a forestry plantation on the Craignish peninsula, Argyll, after being found with the deadly Ramorum infection – the first recorded time in Scotland the disease has been found outwith tree nurseries.

I've done a bit of work on invasive species in Argyll and Bute – and they really have an issue with ponticum there. A study by Forest Research concluded that Rhododendron occupies an area of 4,654 ha in Argyll and Bute (in 2008) of which 85% is located within woodland. Control is being undertaken at only 15% of the area affected and the species could spread by half as much again in 50 years.

The SAF states that it is essential that control is coordinated across ownership and administrative boundaries and that follow-up action is sustained to prevent recolonisation of cleared ground. Although it is difficult to control, there are management options available. Glyphosate is the usual control agent – although I anticipate that could be problematic to use in the water-rich environment I'll be studying in Galloway. Nevertheless, I am looking forward to visiting one of my favourite areas in Scotland in coming months.

Reference: Edwards, C. and Taylor, S. L. (2008). A survey and appraisal of Rhododendron invasion in Argyll and Bute. Forest Research. Reports and a presentation on best-practice control of ponticum, can be found at: http://www.forestresearch.gov.uk/fr/INFD-7DYGEN