Poplar rusts in Australia with comments on potential conifer rusts.

Melampsora medusae Thüm. and M. larici-populina Kleb. are the most popular conifer rusts, that have been found in Australia. M. medusae and M. larici-populina differ in the size, shape and wall echinulation of the urediniospores, in the apical wall thickness of their uredinial paraphyses, in the position of the telia on the host leaf, and in their host range. M. medusae has the widest host range, but it occurs mainly on Populus deltoides clones and hybrids. M. larici populina occurs mainly on P. nigra var. italica.