Import controls tightened as oak disease threatens Britain’s trees

Fordyce Maxwell


FORESTERS, tree nurseries and garden centres throughout Britain have been put on full alert against the threat of "sudden oak death".

The disease, caused by a microscopic fungus called Phytophtora ramorum, has killed thousands of oaks in California and Oregon since it was identified in 1995. It can also affect rhododendron and viburnum and evidence of it has been found at four nurseries in West Sussex, Dorset, Lincolnshire and Lancashire.

It has been found on shrubs in Germany and the Netherlands and it is understood that two of the UK infections were found on imports from Holland.

The Department of the Environment, Food and Rural Affairs (DEFRA) and the Forestry Commission are playing down fears of a tree-killing epidemic similar to Dutch-elm disease.

But a ban has been imposed on plants from some parts of the US and extra controls have been imposed on wood imports.

Roddie Burgess, the spokesman for the Forestry Commission, said yesterday: "Some infected viburnum plants have been found and these have been destroyed.

"On trees, the disease causes lesions in the bark which splits and oozes reddish-black material and they die quickly. But it can be confused with other tree infections and laboratory tests are needed for positive identification."

Scientists believe European and British oaks - there are an estimated 212 million in the UK, 15 million of them in Scotland - are more resistant to the fungus than the US varieties.

But there are other fears that beech could be affected. In susceptible shrubs, such as ornamental rhododendron, the fungus attacks and discolours the leaves, but is seldom fatal.

Mr Burgess said: "It’s far too early to talk about a Dutch-elm type disease. We might have been caught out by that, but we have learned a lot since then. That’s why we’re acting now and shutting the door."

To do that, a number of rules have been imposed or tightened. Rhododendron, viburnum, and oak plants or seeds from areas of the US where the disease is known to occur are banned, and existing controls on imported oak wood now include material derived from all host trees originating in the affected areas of the US.

DEFRA will also have to be told of commercial deliveries of host plants of any origin into and within England and Wales. Imports of oak wood from North America are already subject to measures, such as the removal of bark to reduce other risks.

The government has urged the European Commission to require member states to carry out surveys of potential host material this summer and to report their findings later this year. The commission has already agreed to draft measures for consideration at the next meeting of its plant health committee.

The tiny fungus, Phytophthora ramorum, is distantly related to the potato blight fungus, but scientists say it is not matched by any of the 60 previously known Phytophthora.

The fungus can be spread in soil and rainwater, but most usually by infected wood or plants. It seems to do best in moist atmospheres, but could be vulnerable to low temperatures.