Brighton in Sussex is home to Britain’s largest population of Elm trees. These 19,000 elm trees are known as The National Collection. Elm trees are increasingly rare due to the blight brought by Dutch Elm disease principally in the 1970s.  Initially this came into the UK as long ago as 1926.  Dutch Elm disease is a fungus carried by beetles and affects only elm trees. In response to this attack, an elm tree will automatically produce tyloses, an effective natural defence against the 1926 strain of Dutch Elm disease. Tyloses occur in the xylem - water conducting vessels of the plant / tree, sealing them off and restricting the movement of the pathogen. However in the early 1970's,  a new strain of Dutch Elm disease was imported from channel ports, linked directly to the Canadian Rock Elm. This strain travels faster through the elm trees and kills them before they can produce tyloses. Since the introduction of this strain of Dutch Elm disease to Britain, the number of elm trees has gone down from about 3 million to fewer than 200,000 and many of these are very young ones which will certainly succumb to the disease. Elm trees reproduce by root stalks more often than by seed and so this transmission mechanism quickly spreads the disease between elm trees and along elm hedgerows. Read more...