Speaking at the Four Oaks Trade Show, FERA plant health inspector Martin Parry said elm trees that are resistant to Dutch elm disease being imported from areas such as Italy have been found to be infected by elm yellows virus and they have been intercepted.
Symptoms of the disease range from yellowing of the leaves to dieback of foliage and branches. FERA detected it in the UK for the first time in spring 2014 and issued a fact sheet this April.
The phytoplasma bacterium affects Ulmus Americana, U. alata, U. serotina and U. rubra. U. chemoui, U. japonica and U. parvifolia are less susceptible, while U. minor and U. glabra are little affected. Leafhoppers spread the disease and there is no known treatment.
Parry pointed out that since FERA banned ash trade because of the influx of ash dieback in October 2012 no real progress has been made towards finding a resistant strain. "Similar to Dutch elm disease, it will take 20 years to find a resistant strain."
He added: "Ash dieback brought things to public attention. There was more political change than anything FERA did. Our political masters will determine what resources go into things. We're civil servants directed by Government."
Parry said there is likely to be another public engagement exhibit at the RHS Chelsea Flower Show in 2015. It will "ask people to be careful about where you buy plants", he added.
For information on symptoms and treatments for Elm yellows see the Forestry Commission's Elm yellows factsheet.