Published online by Cambridge University Press: 01 July 2016
Over the last four years the Forestry Commission has conducted sample surveys to estimate the spread of Dutch Elm disease in England and Wales. The data were described and some of the problems of making inferences from them were indicated. These include the definition of an individual elm tree, the two main modes of infection, the complexity of the spatial distribution of elms and the existence of at least two strains of the fungus C. ulmi with different pathogenicity.