In the spring, the very first spores, spermatogonia, arise out of the debris on the ground and infects the young stem, distorting them and producing orange pustules. These pustules break open and infect the leaves. In the Summer, these darker orange spores called urediniospores spread through the wind. Eventually, in late August, the urediniospores and sori become speckled with black fascicles and dark resting spores called teliospores. The teliospores turn into aeciospores which are the spores that adhere to stems and leaves to overwinter. like all rusts, infects host tissue and feed on healthy cells, not able to survive on dead plant material, so must either alternate with a different, perennial host or produce a resting spore to pass the dormant season.
Only attack roses and pass the winter as resting spores.