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Gardeners warned after never-before-seen pest, which covers trees in 'unsightly' white strands, found in UK

The RHS has warned that more and more devastating garden pests are invading the UK from abroad - PA
The RHS has warned that more and more devastating garden pests are invading the UK from abroad - PA

Gardeners have been warned to look out for a new pest, which has never been seen before in the UK, which covers popular garden trees in unsightly white strands.

Cotton stringy scale is a pest usually found in Asia and parts of Italy that is thought to be attracted to magnolia, mulberry and dogwood trees - and it is suspected to have been brought to the UK for the first time on a plant imported from abroad.

The Royal Horticultural Society has warned of the pest which can be a nuisance to gardeners and is easily spread, as the eggs are carried in the wind.

Their head of plant health head of plant health Gerard Clover told The Telegraph: "Many of the UK’s 27 million gardeners take pride in their green space and the unsightly appearance of cotton stringy scale will be an unwelcome addition.

"Its anticipated spread is a reminder of the battle we face in preventing new pests and diseases from finding their way into the UK and protecting our gardens for the future. To reduce the risks from new problems it is important that gardeners are aware of plant health threats and how to mitigate them."

The pest has spread around the world because of plant trade and is prevalent in parts of Italy.

The RHS is keen to hear from gardeners who find the pest in their garden so that it can build a picture of host plants in the UK and tailor advice to gardeners.

Magnolias, mulberries, elders, sycamores and dogwoods are thought to be a favourite. Gardeners are encouraged, where practical, to remove egg masses with a stiff brush and water.

An RHS spokesperson said: "Given that many plants are grown for their blooms, foliage or textured stems and branches, the pest could certainly lessen their enjoyment.

"If it proves impossible to remove [with a brush and water] and its aesthetics are considered too much to bear a pesticide can be applied strictly according to label instructions, this is likely to be most effective when the eggs hatch in summer."

Pests which mar and destroy gardens have been brought in from abroad in recent years, sometimes to devastating effect.

The RHS identified one new plant disease last year – a Phytophora on a Water Iris - and in previous years their identification includes deadly diseases which have taken hold in gardens across the UK, including Box blight in the 1990s, Escallonia leaf blight in 2007 and Kerria twig blight in 2014.

The Fuchsia Gall mite, discovered in the UK by the RHS in 2007,  is now causing real problems for fuchsia growers in the South East.

The spokesperson added: "The arrival of the cotton stringy scale in the UK is evidence of the need for biosecurity issues to remain a top priority – not all of them promise to be as benign.

"There are currently more than 1,000 plant pests and diseases on the risk register including Xylella – a bacterium which is known to affect more than 350 species of plant, including garden favourites such as lavender, hebe and rosemary - has been found in Italy, France and Spain."