It might be a good idea. Find out, if you can every hear back from your county agent (ours in L.A. County has what amounts to a FAQ on voicemail!), if perhaps using some liquid fungicide, such as Funginex or Neem oil might help. I find Neem oil to be very beneficial in combating fungus on roses, FWI. Just a thought. Would never want to suggest anything that might do violence to your plants(s). Ron