The arrival of a new species of the fungus which causes Dutch elm disease into Great Britain in the 1960s caused widespread elm death and continues to be problematic following elm regeneration. Attempts at managing the disease have been largely unsuccessful. Forty years after the outbreak, however, researchers continue to be interested in both the underlying biology of such a severe and dramatic disease event and in the policy lessons that can be drawn from it. We develop a spatial model at a 1 km 2 resolution. Following parameterization to replay the historical epidemic, the model is used to explore previously proposed counterfactual management strategies. A new introduction date of late 1962 is estimated. We show that, even had there been high intervention at a national level in terms of disease management early in the epidemic, there would have been little long-term effect on elm numbers. In Brighton, a local pocket of elm which survived the peak of the initial epidemic has been successfully managed. However, Brighton and similar locations are subject to repeated waves of the disease at a 15-to 20-year intervals following regeneration and reinfection of the surrounding areas, during which much more intensive management is required.Keywords: epidemiology, Ophiostoma novo-ulmi, spatial modelling, Ulmus
IntroductionThroughout the 1970s an epidemic of a newly introduced Dutch elm disease fungus swept through Britain, killing the majority of mature elm trees (Gibbs, 1978a;Jones, 1981). The epidemic was caused by the scolytid bark beetle-borne fungus Ophiostoma novo-ulmi Brasier & Kirk, 2001), a new species which had not been identified at the time of introduction. This fungus had been causing widespread elm death in North America, in conjunction with the original Dutch elm disease fungus O. ulmi, which had been introduced from Europe (Gibbs, 1978b). In North America, the native elm species were very susceptible to both pathogens, and a distinction had not been made between them, although a change of disease intensity was identified (Pomerleau, 1961).In Europe, the original fungus had been causing elm death since at least the 1920s, when it was first identified. In Britain, the official line (Peace, 1960) was that the disease did not justify significant government intervention since a degree of recovery could be expected, and epidemic flareups were localized (provided that the disease did not change its character). Following the introduction of the new fungus on infected timber from Canada , there was a resurgence of the disease. In a recent analysis of the science and policy of the epidemic, Tomlinson & Potter (2010) record how the received wisdom of Peace, widely disseminated and largely accepted within plant pathology circles, had the effect of delaying a response, as the resurgence was understandably perceived as a local flareup of O. ulmi. Hindsight suggests that the potential existed for the new fungal species to be identified outside Britain, and that management could have been better coordinated and managed...
