Dutch elm disease (DED) first appeared in the north-west of Europe around 1910. Between 1914 and 1919, several female Dutch scientists carried out influential research on the cause of the disease. Then in the late 1920s Dr Tom Peace of the UK Forestry Commission began to monitor its rapid spread to Britain.
The first epidemic caused losses of 10-40% of elms in various European countries. But by the 1940’s this first epidemic died down and in 1960 Dr Peace was able to write that "unless it completely changes its present trend of behaviour it will never bring about the disaster once considered imminent". However such a change did come in the late 1960s with the beginning of a second and far more destructive outbreak of the disease.
Forestry Commission research showed that the new outbreak of DED was caused by an entirely different, far more aggressive species of DED fungus that had been imported into Britain on elm logs from Canada.
Container of rock elm imported with Dutch elm disease and Hylurgopinus rufipes larvae.
What followed was the catastrophic epidemic once feared by Peace:
- Within a decade about 20 million of the UK’s 30 million elms were dead
- By the 2010 it was considered some 60 million elm trees have been lost to the disease.
Studies on the new DED fungus showed that it differed from the original fungus in almost all its important biological properties. The two pathogens were later described as separate species:
- Ophiostoma ulmi - caused the original epidemic
- O. novo-ulmi - a new highly aggressive pathogen that caused the second epidemic