American ash trees could protect British woodlands Infected trees have now been found on land owned by both the Highways Agency and Network Rail, raising fears that the fungus could be spread further around the country on leaves picked up by passing cars or trains. A spokesman for Network Rail, one of the biggest landowners in the country, said a survey on its land has shown it has 400,000 ash trees, with 250,000 in the age range considered to be most at risk. The Highways Agency said it had found infected trees at two locations - on the A1 near Leeming in North Yorkshire and the A12 near Ipswich in Suffolk. The Forestry Commission is conducting tests to find varieties of trees that can be used to replace ash, which currently make up a third of the country's woodland. In Poland and Denmark, around 90 per cent of the ash trees have been infected with the fungus. However, preliminary findings by Dr Heinrich Lösing of the Nurseries Association of Schleswig-Holstein, in Germany, has shown that the green ash, Fraxinus pennsylvanica, and white ash, Fraxinus americana, do not appear to be infected by Chalara. Dr Peter Saville, a retired reader in forestry at Oxford University and chairman of the Future Trees Trust, which has been attempting to increase the genetic diversity of trees in the UK, said: "Hybridising British ash trees with those from America and Asia may give the best long term solution to ash dieback. Although it is not a fast process, the latest advances in genetics has made it a lot easier.