Pathogenicity of Xylella fastidiosa in American Elm and Failure of Reciprocal Transmission Between Strains from Elm and Sycamore. J. L. Sherald, Plant Pathologist, Center for Urban Ecology, National Park Service, 1100 Ohio Drive S.W., Washington, DC 20242. . Plant Dis. 77:190-193. Accepted for publication 15 October 1992. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1993. DOI: 10.1094/PD-77-0190.

Pathogenicity of Xylella fastidiosa was demonstrated in American elm seedlings. Ten 4-mo-old seedlings were stem-inoculated with a pure culture of X. fastidiosa obtained from a naturally infected elm. One year after inoculation, all inoculated seedlings developed leaf scorch symptoms characteristic of naturally infected trees. X. fastidiosa was isolated from six inoculated seedlings but not from 10 symptomless control seedlings. Isolates of X. fastidiosa obtained from a naturally infected elm and a previously inoculated sycamore were pathogenic in seedlings of elm and sycamore, respectively, but not in reciprocal hosts.