A fungal disease, disseminated by various elm bark beetles. The original strain, Ophiostoma ulmi, mutated after an earlier infection killed 10-15% of the UK’s elms in the 1930s. Returning as Ophiostoma novo-ulmi, DEDkilled 25 million elms in the UK in the 1960-70s. It remains present and now threatens the few survivors, notably in Brighton. Efforts to replant using ‘disease-resistant strains’ have not been successful on any scale and naturally-growing elms tend to succumb when they reach 8-10 years and are large enough to interest the beetles which carry the infection.
What we can learn from this large-scale disaster is that the search for ‘disease-resistant strains’ has not provided a solution for elm. The lost trees have never been successfully replaced and 40-50 years later, the disease is still present in the UK and is slowly infiltrating Brighton – one of the last outposts of the elm in the UK.