Ailanthus glandulosa is an introduced tree species in Greece used as ornamental and is considered resistant to both fungal and insect attacks. However, since 1992, a great number of A. glandulosa plants of different ages and in different parts of northern Greece have been dying. The phenomenon appeared either in single trees or in groups, and the number of affected plants increased from year to year. The symptoms were characteristic of a wilt disease. Dieback started on one or more branches and gradually spread, or whole trees were affected from the beginning. Death may occur during spring when trees do not resume their activity or later in the summer. Leaves wilt, turn yellow and fall in a short time. Trees may die in 1 to 3 years depending on their age. In cross sections of branches a continuous discoloured ring or arc was present in the outermost sapwood. Isolations made from dying trees from 25 different locations have yielded V. dahliae, a pathogen known to cause vascular wilt on many plant hosts, including Ailanthus (1). Isolations made from healthy trees did not yield the fungus. Abundant mycelium developed in the host vessels of infected trees; the hyphae were cylindrical, hyaline, and septate. On malt agar fungal cultures developed quickly and were initially a whitish to cream color that later turned black due to the formation of microsclerotia. In culture, microsclerotia started to form centrally and were dark brown to black, consisting of swollen globular cells that formed irregular masses variable in shape. The fungus also produced abundant verticillate conidiophores with phialides and conidia. This is a first report of Verticillium wilt on A. glandulosa in Greece.
Reference: (1) G. Arnaud et al. Rev. Pathol. Veg. Entomol. Agric. Fr. 17:227, 1930.