Relatedness of Mycoplasmalike Organisms Associated with Ash Yellows and Lilac Witches'-Broom

The mycoplasmal diseases ash yellows (AshY) and lilac witches'-broom (LWB) were diagnosed on the basis of symptoms and the DAPI (4',6-diamidino-2-phenylindole.2HCl) fluorescence test in 12 taxa of Fraxinus and 35 taxa of Syringa, respectively, at the Arnold Arboretum, Jamaica Plain, MA. AshY and LWB also occurred together in other arboreta in the United States and Canada. Ash mycoplasmalike organisms (MLOs) were transmitted to lilacs, and lilac MLOs were transmitted to ash by dodder (Cuscuta spp.)