Dame Helen Mirren has added her voice to an RHS campaign urging holidaymakers not to bring plants back from abroad this summer to help halt the spread of the deadly bacterium Xylella fastidiosa.

The multi award winning actress has witnessed the devastating impact of Xylella in Italy, where it is thought more than 11 million olive trees have already fallen victim. 

The disease prevents plants from transporting water and is known to infect more than 500 different plant species with garden favourites including lavender, oleander, rosemary and flowering cherry all at risk in the UK.

If found in the UK, all host plants within 100m would be destroyed and there would be restrictions on movement of specified plants within a five km radius for up to five years - striking a death knell for gardens and horticultural businesses.

Dame Helen Mirren said: “I have witnessed first-hand the destruction that Xylella causes in Puglia, Italy – devastating (almost overnight) countless centuries-old olive trees in the businesses and communities that have long relied on them. 

“Preventing Xylella’s spread is a priority and something that UK holidaymakers can support by simply avoiding bringing plants back from abroad that may be harbouring the bacterium.

“Our gardens and green spaces are vital for people and the planet and a failure to act could mean the landscapes that define us could be irreversibly changed. We desperately need more scientific research and support to ensure we can protect the historic Italian landscape and our British gardens and natural habitats for the future.” 

Gerard Clover, Head of Plant Health at the RHS, added: “While importing plants in personal baggage is already subject to some restrictions we are calling on holidaymakers not to bring plants back from abroad and instead purchase them in the UK. 

“Several pests and diseases are already thought to have made their way into our gardens through private importations, such as fuchsia gall mite, and we simply cannot afford for Xylella to follow.”

The initiative complements Defra’s ‘Don’t Risk It’ campaign, which continues this summer and raises awareness of the risks of bringing back plants, cut flowers, fruit and vegetables from holiday destinations. 

If you have enjoyed seeing a certain plant or tree on your travels and want to enjoy it in your own garden, you should always buy directly from a UK garden centre or supplier. That way you can be sure that it has been sourced responsibly and gone through the necessary checks for pests and diseases.

The RHS is also working as part of a UK Research and Innovation-funded consortium called BRIGIT, supported by Defra and the Scottish government, to enhance UK surveillance and response to Xylella fastidiosa. Volunteers are being asked to report sightings of spittlebugs in gardens and green spaces; spittlebugs are not plant pests, and should therefore be left alone, but do carry Xylella on the continent where the disease has been found.