72 volunteers took to the bracken-clad slopes around Rydal in the Lake District to pull out around 640,000 Himalayan Balsam plants.

The Big Balsam Bash event was organised by South Cumbria Rivers Trust and charity Friends of the Lake District.

Jayne Wilkinson, catchment planning and monitoring officer with South Cumbria Rivers Trust, said: "Once it’s established, Himalayan Balsam quickly dominates, out-competing native wildflowers and leaving soils bare and susceptible to erosion when the plants die back in winter."

She added: "The infestation of Himalayan Balsam at Rydal is on a large scale so it is fantastic that so many people came out and joined in the fight to help us control this ‘alien’ invasive species.

"Rivers are particularly good transport systems for the seeds and by controlling the plant in the upper reaches of a catchment we can stop or reduce its spread downstream."

Ruth Kirk, landscape engagement officer with Friends of the Lake District, said: "The statistics from the day are pretty impressive – around 640,000 individual plants were pulled - although we would far rather there was no need for us to undertake this work in the first place.

"The Fight the Aliens Big Balsam Bash was a fine example of partnership working in the Lake District at its best."

Another, smaller scale event is planned for Wednesday, August 21 to get the remaining plants that may have been missed first time round.

Anyone interested in taking part should contact ruth-kirk@fld.org.uk or visit www.friendsofthelakedistrict.org.uk for more information.