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Killer fungus deployed in battle against alien invaders in the Broads

PUBLISHED: 13:18 04 September 2019 | UPDATED: 13:19 04 September 2019

Himalayan Balsam (Impatiens glandulifera) has become a major problem in the Norfolk Broads. Picture: GB Non-Native Species Secretariat (GBNNSS).

Himalayan Balsam (Impatiens glandulifera) has become a major problem in the Norfolk Broads. Picture: GB Non-Native Species Secretariat (GBNNSS).

GB Non-Native Species Secretariat (GBNNSS)

A killer fungus has been deployed as a biological weapon against alien invaders sweeping across the Norfolk Broads.

An infected Himalayan balsam plant with pink spotting on its stem. Picture: Broads AuthorityAn infected Himalayan balsam plant with pink spotting on its stem. Picture: Broads Authority

Himalayan balsam, a waterside-loving weed with attractive pink flowers, is spreading so rapidly in the Broads that scientists have become concerned about its impact on the riverbanks and biodiversity, as it out-competes native plants and increases the risk of soil erosion and flooding.

Tackling the invasive species can be difficult and expensive, with the Environment Agency estimating that the current cost of around £1m per year would need to rise to £300m to eradicate it entirely from the UK.

But scientists have been encouraged by the results of a Norfolk project which uses a natural agent in a targeted attack against the alien plants.

Last year, a research team released Himalayan balsam plants infected with a killer "rust fungus" onto sites around the banks of rivers Wensum, Glaven and Bure.

An infected Himalayan balsam plant with brown mottled leaves. Picture: Broads AuthorityAn infected Himalayan balsam plant with brown mottled leaves. Picture: Broads Authority

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.

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 added: "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."

Jim Papworth, estate director for Wroxham Home Farms Estate, is one land manager battling the scourge of Himalayan balsam.

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."

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. Signs include mottled brown leaves and pink spots on the plant stems.

- For more information see the Non Native Species Initiative website.

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