Definition of elm yellows
: a usually fatal disease of North American elms (such as the American elm) that is characterized by yellowish, often black-flecked discoloration and degeneration of the phloem and that results in death of the root system followed by wilting, yellowing, and loss of leaves
Note:
Elm yellows is caused by a phytoplasma transmitted by a leafhopper (especially Scaphoideus luteolus).
— called also
phloem necrosis 
