mine does not get mildew. its been getting the brown spots. but been spraying with the liquid copper. I have had this plant going on 12 years. first I tucked it near the lilac tree as I had moved it from an original location where it would have died---too much wet soil. So it stayed in a very shady area totally not tended to at all but survived. Finally I arranged the spot its in now, so this is its 2 years in the new spot, and growing like gang busters, it gets some sun, not harsh direct with dappled shade during the day as the sun moves. Giving me lots of blooms, and new canes. Seems happy except for the brown spots, but they just started so I have been spraying. And yes, not one thorn on it.