Infected young green shoots may also exhibit long, narrow, orange pustules. The stem lesions may cause twisting of the shoot and destruction of buds.
Spores form on fallen infected leaves in early spring.
Spring infections form minute yellow cups of spores on the undersides of rose leaves. The spores become orange in reddish orange cups by summer. These spores repeatedly reinfect the rose. By late fall, the spores are black. These black spores overwinter on fallen leaves and form microscopic, colorless spores that infect leaves in spring.