First report of the telial stage of Japanese apple rust on Juniperus chinensis in North America and the aecial stage on Malus domestica.
Following a report in April 2009 of the presence of Gymnosporangium yamadae on crabapple (Malus toringo) in Wilmington, Delaware, USA, a study was conducted to confirm and document the pathogen. During April 2009 site visit, ornamental Juniperus chinensis were observed near the original crabapples. On 7 May 2009, telial galls were collected from the ornamental J. chinensis at the Wilmington site. The telia were confirmed to be G. yamadae by morphometric analysis and molecular data. On 4 August 2009, leaves of M. domestica at the University of Delaware in Newark were confirmed to have G. yamadae infection. Identification was made on the morphological presence of unique roestelioid aecia with long cornulated peridia that lacerate along the sides. This is thought to be the first report of the telial stage of G. yamadae in North America and the first report of this pathogen on M. domestica in the USA.