Ulmus Minor Subsp. minor - Pests and Diseases

Pests and Diseases

Although the Smooth-leafed Elm is generally susceptible to Dutch elm disease, it is genetically a highly variable tree and it is possible some specimens survive in the UK owing to an innately high level of resistance (see Cultivation). Research currently (2009) in hand by Cemagref at Le Pepiniére forestiére de l’Etat, Guémené-Penfao, France, should confirm this. However, all Smooth-leafed Elm varieties are believed to have been introduced into Britain from central and southern Europe during the Bronze Age, and some, being beyond their natural climates and environments, may be growing slowly and thus producing smaller springwood vessels restrictive to the Ophiostoma fungus. Good performance in the field may also be owing to resistance to bark beetle feeding or breeding. Moreover, several types of this subspecies also have very pendulous twigs when mature, a factor which could also make them unattractive to foraging beetles. Of over twenty mature elms of various species, including hybrids and cultivars, in the elm collection of the Royal Botanic Garden Edinburgh in 1990, only four specimens survive in 2012: two of them are U. minor subsp. minor types with pendulous twigs (the other two are Ulmus glabra 'Exoniensis' and Ulmus pumila).

The subspecies has a moderate to high susceptibility to the elm leaf beetle Xanthogaleruca luteola, and a moderate susceptibility to Elm Yellows.