It is reported that the authorities are considering restricting the importation of plants from the United States to protect Britain’s oaks from a disease that could depopulate our ancient woodlands.

The problem is a fungus-like disease known as “Sudden oak death” which was initially brought in by plants imported from Asia. It is so potent that it can kill oaks within a few weeks of infection. Concerns are now being raised about imports from the USA where a second form of the disease has been diagnosed. This variant also attacks ash, beech and other species including bilberry and Scottish heather.

Already outbreaks of the disease, also called phytophthora ramorum, have been identified at over 600 sites in England and Wales and many others in Scotland.

The infestation normally begins to manifest itself with brown and black blotching on the leaves and twigs, before developing into oozing cankers on the trunk, leading to rotting and death. Experts fear it is spreading so fast that it could have the same impact as Dutch elm disease, which is estimated to have killed 25 million elms during the twenty year period beginning 1965

This week a report from the Royal Horticultural Society (RHS) is to be released. This will warn that the number of disease outbreaks on all types of plant is up 60% on last year. It claims this is linked with the surge in imports of exotic foreign plants. British consumers spent £870m on them in 2005

The RHS report adds: “Alien pests and diseases, inadvertently imported on exotic plants, are threatening the plants in our gardens and across the countryside. Increased global plant trade, coupled with evidence of rapid climate change, suggests that the problem will only get worse”.

One option in countering the threat of sudden oak death is said to be extending the existing “plant passport” system controlled by the EU, which restricts the import of vulnerable species, especially rhododendrons, from infected parts of America.

Simon Thornton-Wood, the director of science and learning at the RHS, said: “This disease is hard to control. It has killed a lot of trees in America and we need to take it very seriously”.

Land & People agrees �“ we have already seen what the importation of the North American grey squirrel has done to our indigenous red, we need to ensure that our oaks and other native species are protected from alien species of flora.