Natural killer of Himalayan Balsam offers hope for tackling troublesome invader

Scientists and land managers have been enthused by promising results from a research site in the Broads National Park, where a killer ‘rust fungus’, which attacks the alien Himalayan Balsam is slowly spreading.

Himalayan Balsam (Impatiens glandulifera) copyright GBNNSS

With its attractive pink flowers, this waterside-loving plant is invading the Broads so rapidly that scientists are concerned by its negative impact upon the riverbank and biodiversity. It out-competes native plants and increases the risk of soil erosion and flooding.

Many land managers struggle to control Himalayan Balsam and resort to expensive measures to halt its advance. The Environment Agency estimate that current measures to tackle the weed cost around £1 million annually, but would rise to £300 million to eradicate it entirely from the UK.

Last year, a research team released Himalayan Balsam plants infected with the killer rust-fungus onto sites around the banks of rivers Wensum, Glaven and Bure. The team, from the ‘RAPID LIFE’ project, the Norfolk Non-Native Species Initiative and the Broads Authority, have since observed the diseased plants spreading through the National Park area.

Joe Kenworthy, Coordinator of the Norfolk Non-Native Species Initiative said,

“Not all plant diseases are bad. This helpful fungus has been carefully tested in the lab and the field to target only Himalayan Balsam, without having a negative impact upon other plants and animals. In the long term, we hope to see native species returning, binding soil together on riverbanks and thus reducing the risk of soil erosion.”

Broads Authority Senior Ecologist, Andrea Kelly, said of the experiment,

“We tend to think of Himalayan Balsam as growing along the riverbanks but recently it has been found taking over other wetland habitats, adding to the reasons why we need this rust fungus to work.”

The pink stem of an infected Himalayan Balsam plant

Wroxham Home Farms Estate Director, Jim Papworth was encouraged by the results on the estate. He said,

“Himalayan Balsam is everywhere, not just along the edge of the Broads. It spreads so fast; you don’t see it one year and then the next year there’s an explosion.

“There are so many places where it grows that are inaccessible to cut it back, so if this method works it could be ideal.”

Joe’s advice for land managers is to keep on tackling Himalayan Balsam. He said,

“Work with your neighbours upstream because that’s the route by which it spreads.

“These are early days and other treatment methods will still be necessary, but in the long term if this rust fungus takes hold, the wider environmental and financial savings could be significant.”

Farmers and landowners are being asked to help scientists by looking out for signs that diseased Himalayan Balsam plants are spreading through the Broads National Park area. The fungus survives in the leaf litter over winter and infects new seedlings. Signs include mottled brown leaves and pink spots on the plant stems. For more information on Himalayan Balsam see the Non Native Species Initiative website.

Wednesday 4 September 2019