I just impulsively bought a Double Delight rose and have since been learning online that it's a terrible blackspot magnet. I've also heard that fungicide sprays are not available in Canada. (I'm in Courtenay, BC) But I do have Safer's sulphur dust. Has anyone had good results with this? How do I use it? How often do I reapply it? And does it work better as a dusting, or dissolved in water and sprayed? The outlook is that our summer is likely to be hot and dry, so I'm hoping blackspot and mildew may be less of a problem than usual.