Phytoplasma diseases of trees and shrubs of urban areas in Europe

In Europe, phytoplasmas cause severe yellows, witches'-broom and decline diseases of trees and shrubs grown in urban areas. Spanish broom (Spartium junceum) is affected by the spartium witches'-broom disease which is associated with phytoplasmas,of the apple proliferation (AP) and elm yellows (EY) groups. Broom (Sarothamnus scoparius) and buckthorn (Rhamnus catharticus) are affected by lethal witches'-broom diseases whose causal agents are distinct members of the AP group. An important disease of elm (Ulmus minor and others) is elm yellows, which is caused by the EY phytoplasma. Alder (Alnus glutinosa and others) and eucalyptus (Eucalyptus spp.) are affected by alder yellows and eucalyptus little-leaf disease, respectively, both induced by phytoplasmas closely related to the EY agent. Yellows diseases associated with phytoplasmas of the aster yellows group affect several species of poplar including Populus nigra 'Italica', P. alba, and P. tremula. Ornamental apples (Malus spp.) and flowering cherry (Prunus serrulata) are affected by apple proliferation and European stone fruit yellows, respectively. Other trees and shrubs affected by phytoplasmoses include black locust (Robinia pseudoacacia), hazel (Corylus maxima and C. colurna), northern red oak (Quercus rubra), hawthorn (Crataegus monogina) and weeping-willow (Salix babylonica). However, the identity of the phytoplasmas infecting these species has never been determined.