Hybrid Rugosa cultivars are very resistant to blackspot and powdery mildew in comparison to other rose cultivars. Leaf spots can occur but are not common. Rust was the most common disease problem of the group. Agnes , Blanc Double de Coubert , Delicata , Grootendorst Supreme , Pink Grootendorst , and Sir Thomas Lipton were also very healthy with only light infections of leaf spots or rust. There are no identifiable trends in disease resistance among the Shrub Roses, probably due to the heterogeneous genetic backgrounds of this group.
Diseases do occur, particularily blackspot and leaf spots.
Although the summers of 1990 and 1992 provided excellent conditions for disease development, most infections on the Shrub Roses were slight to moderate. Applejack and Summer Wind were disease-free in 1990 and 1992. Bonica , Carefree Beauty , Chamcook , Champlain , Golden Wings , Haidee , John Franklin , Lillian Gibson , and Prairie Wren were also very healthy. Species Roses, like the Shrub Roses, usually have slight to moderate levels of disease incidence. Rosa arkansana and R. rugosa kamtchatica can be noted for their high susceptibility to powdery mildew, and severe infections of blackspot were seen on R. canina , R. foetida , R. foetida bicolor , R. glauca , and R. woodsii in either or both of the years 1990 and 1992.