They enlarge to form reddish brown angular spots visible on lower and upper leaf surfaces approximately 0.5 cm - 1 cm in diameter.
Leaves are the only plant part affected.
When disease is severe, yellowing and defoliation can occur in late summer and early autumn. New leaves then produced by the tree are at risk from damage by frost. Fruiting structures can be seen within the spots on the undersides of the leaves. Only the uredinial stage is known in the U.S. Uredinia are initially cream to salmon color later turning yellow. Uredospores are cream to white in color and are produced in short chains.