Gardeners and horticulturalists have been warned to look out for one of the deadliest plant pathogens after it wiped out thousands of trees in southern Europe.
Xylella fastidiosa can kill or damage more than 350 species of tree and shrub by affecting their ability to draw water from the soil. It is a bacterial pest spread by common insects including aphids and froghoppers.
No cases have been reported in the UK and gardeners are being urged to buy British to reduce the chance of it arriving on imported plants.
Gerard Clover, head of plant health at the Royal Horticultural Society, described X. fastidiosa as a game changer that has the potential to kill millions of trees, devastate crops and transform the British landscape.
Dr Clover said: “Xylella is in a class of its own because it kills plants, has insect vectors and such a broad host range.”
The disease arrived in Europe from the Americas and has wiped out whole olive groves in southern Italy. It has since spread to Corsica and elsewhere in mainland Europe, where it has infected grape vines and scores of other plants.
There is no effective treatment for the bacterial infection other than to prevent it being spread by insects with the use of pesticides. Not only does it attack a wide range of plants but its symptoms mimic several other problems such as drought and frost damage, making it difficult to diagnose.
Many garden favourites including flowering cherry, lavender and rosemary are at risk. Potential cases of the disease should be reported to the department for environment, food and rural affairs.
Dr Clover added: “The RHS views the threat of Xylella as a pivotal point in the future of plant health in the UK and as such we have opted to increase our plant health provisions to counter the threat from the bacteria as well as the myriad other pests and diseases knocking at the garden gate.”
Michael Gove, the environment secretary, has urged the EU to introduce more checks on high-risk plants being moved between countries.
The RHS has clamped down on imports. All imported semi-mature trees will be held in isolation for 12 months before they are planted at RHS gardens and shows, where possible, and evaluation of plant health risk will be incorporated into judging criteria at RHS flower shows.
A spokesman for the environment department said that the threat from diseases such as X. fastidiosa was a “very real and growing concern”.
He said: “That is why this year we have pressed hard at EU level for increased protections against Xylella, in order to prevent the devastating disease reaching our shores, and these were approved in October and came into force this month.”