It depends, In the cooler months I mix Daconil and Propaconizole together in one spray tank and apply it twice a month. In warmer weather I rotate with either Immunox or Theophanate Methyl, or Propaconizole mixed with Dithane. Rotation is key so blackspot doesn't develop resistance. My spray period is March through October. If we go through a hot and dry period, I usually quit spraying for that time since the warm and dry weather naturally reduces disease. I don't spray my OGRs or Shrub roses and they do fine. This program is for picky hybrid teas, like Peace, Brandy, Papa Meilland. I can grow Mr. Lincoln or floribundas like Valentine without spraying but I love yellos and orange long stemmed HTs as well