Imported Dutch elm disease-resistant elm trees could introduce the elm yellows (EY) virus into Britain's already beleaguered elm population, Forest Research has warned, as industry views are sought on a response to the threat.
Defra and the devolved authorities are currently consulting with stakeholders to develop a UK position on the virus, also known as elm phloem necrosis, which is spread by insects and by vegetative propagation.
The consultation proposes a choice of two courses of action:
- A surveillance and awareness-raising programme, to determine whether additional EU or national legal requirements would be justified, before the start of the next planting season;
- the same but with restrictions on imports and movements of elm put in place in the interim.
The plant health authorities already intend to trace and destroy trees known to be associated with infected batches.
Elm will also be added to the list of plant genera whose importation from other EU states must be notified to the authorities.
The disease is widespread in North America and there have been a number of outbreaks in Italy, France and Germany. It was detected in a batch of Italian DED-resistant 'Morfeo' elms being trialled in the UK in 2012.
According to an assessment by Forest Research, "The use of resistant elm material from elm breeding programmes in Europe has raised the possibility that EY could be introduced into the UK via planting stock potentially exposed to this disease in the original place of production."
The UK native field elm (Ulmus minor) is thought to be susceptible to EY, while the wych elm (U. grabra) appears resistant.