Hillier Nurseries director Hossein Arshadi told HW: "There is a canker attacking London planes, spreading quickly up from southern Europe, that kills trees.
"Also, in the past few years horse chestnuts have been increasingly affected by canker, leaf miner and the oak processionary moth."
Arshadi believes the increase of pests and diseases is one of the disadvantages of importing trees into the UK. He added: "I'm not against nurseries importing young tree and liners to grow them on as they have the expertise to inspect them. But I think the problem is uncontrolled imports by traders who don't detect these things."
Commercial nurseries are checked twice a year by the Plant Health & Seeds Inspectorate but Arshadi is concerned that "it is difficult for local authorities or landscapers to know about pests and diseases. Perhaps there should be a code of practice concerning imported plant material."
Forest Research updated its advisory note on diseases affecting plane trees this week to raise awareness within the industry.
Four pathogens are currently moving through Europe weakening and killing plane trees. Fungus Phellinus punctatus, which causes trees to decay, was seen for the first time in Britain in March, on a plane tree in West Sussex. Symptoms to look out for are the pale buff-coloured cankers, Forest Research pathologist Dr Katherine Tubby said. "They are extremely difficult to see on the mottled bark so it is unlikely that a layperson would identify them. So we are relying on reports from the industry."
Another threat, which is "spreading northwards (through France) at a much faster rate than in the previous decade", is Ceratocystis fimbriata f. sp. platani. Commonly known as "canker stain on plane", it causes severe wilting and tree death. Symptoms are elongated or lens-shaped bark cankers which blacken with age. The disease has not been seen in the UK yet.
- For information see www.forest research.gov.uk and to report sightings call 01420 23000.