Ulmus Glabra - Pests and Diseases

Pests and Diseases

While the species is highly susceptible to Dutch elm disease, it is less favoured as a host by the elm bark beetles which act as vectors. Research in Spain has indicated the presence of a triterpene, alnulin, renders the tree bark less attractive to the beetle than the Field elm. Moreover, once the tree is dying, its bark is quickly colonized by the fungus Phoma, which radically reduces the amount of bark available for the beetle to breed on. The tree usually succumbs to disease a few years after achieving sexual maturity.

In 1998, over 700 healthy, mature trees were discovered on the upper slopes of Mount Šimonka in Slovakia, but it is now believed they had survived courtesy of their isolation from disease-carrying beetles rather than any innate resistance; 50 clones of these trees were presented to HRH The Prince of Wales for planting at his Highgrove Estate, and at Clapham, Yorkshire . Indeed, DNA analysis by Cemagref (now Irstea) in France has determined the genetic diversity within the species is very limited, making the chances of a resistant tree evolving rather remote. Nevertheless, the spread of Dutch elm disease to Scotland has revealed a number of Wych elms apparently surviving there unscathed, prompting the Royal Botanic Garden Edinburgh to clone the trees and inoculate them with the fungus to determine any innate resistance.

In trials conducted in Italy, the tree was found to have a slight to moderate susceptibility to elm yellows, and a high susceptibility to the elm leaf beetle Xanthogaleruca luteola .