CONSERVATIONISTS in South-East Wales are turning to a radical solution to tackle a fast-spreading invasive plant along two of the region's main rivers.

Himalayan balsam may have attractive pink flowers, but the non-native species is harming biodiversity within the catchment areas of the rivers Wye and Usk, smothering other plants and causing excessive erosion of riverbanks in the winter months.

Current methods of tackling the spread take up too much time and money, but in a new approach, bio-scientists will introduce a fungus into the ecosystem to hopefully rid the region's waterways of this harmful weed.

Himalayan balsam was introduced to the UK in the mid-nineteenth century. It can grow to around two metres high, and is known for its exploding seed pods in the autumn months.

The most common way of clearing Himalayan balsam is to uproot, cut, and spray it – but the Wye and Usk Foundation said this method had largely been ineffective.

An extensive and project has resulted in the near complete removal of Himalayan balsam from the River Monnow catchment area in Monmouthshire, but such work is costly and time-consuming.

A new method tackling the species involves the introduction of a specialised fungus into the ecosystem.

Rust fungus has been found in tests to be highly specific to Himalayan balsam, not affecting any other plant species.

In 2010, scientists at the Centre for Agriculture and Bioscience International (CABI), based in Oxfordshire, began testing the use of a rust fungus as a control.

Four years later, the fungus was approved for release by the UK government's Department for Environment, Food and Rural Affairs (DEFRA) – becoming the first fungal biological control agent to be released against a weed anywhere in the European Union.

The Wye and Usk Foundation will now begin a joint venture with CABI to trial the rust at two locations in the Wye catchment.

The initiative is part of the foundation's Restoring Our Amazing River project, funded by DEFRA’s Water Environment Grant.