A Lethal fungal disease is threatening to create an 'ecological disaster' along North Yorkshire's rivers, according to the Environment Agency.

RIVER NIDD: At risk from the spread of phytophthora

Alder trees growing on riverbanks are under threat from phytophthora, a disease which invades their stems and roots.

Environment Agency ecologist Martin Fuller is urging anglers, farmers, walkers and other river users to follow a new code of practice to try to limit the spread of the disease.

"The total destruction of alder populations along our river banks would be an ecological disaster and would completely change the landscape of rivers such as the Nidd," he said.

The River Nidd, which rises above Pateley Bridge and joins the Ouse west of York, is thought to be particularly at risk.

An Environment Agency spokeswoman said: "The banks of the Nidd are pretty much alder dominated, so the concern is that if the disease really takes hold on the Nidd, large areas of alder trees would be wiped out by it."

Phytophthora was first identified in southern England in 1993 and then spread rapidly.

The disease was first spotted in York on the banks of the River Ouse in 1996.

Other cases were spotted in Yorkshire the same year and it is now present on all of the region's main river catchments - although many smaller tributaries remain unaffected.

Although the fungus is not spread by the wind or by other natural means, it can be carried in mud. Anglers, farmers and walkers are thought to play a significant part in its spread.

The agency has responded to the threat by drawing up a code of practice, which suggests that anyone who enters rivers or who walks along the river's edge should:

Clean off all footwear, equipment or machinery before moving upstream or to another watercourse

Wherever possible, delay moving from one catchment to another as the fungal spores only live for a few days

Avoid transferring any river water between watercourses or upstream, and

Anglers should ensure that all tackle is thoroughly dried before they move to another water.

Mr Fuller said: "Whilst our understanding of the disease is incomplete, it is hoped that by following the code of practice, the public can do their bit to stop the spread."

Leaflets about the disease phytophthora are available from the Environment Agency's offices at Coverdale House, Aviator Court, Amy Johnson Way, Clifton Moor, York YO3 4UZ.

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