Here is a picture I submitted for the database which I think is a great example of blackspot. One of my few HTs. I do spray every two weeks but quit for the year back in September. But the Fall has been warm and wet. Most of my roses not quite this desease prone but eventually this would happen to them all if I never sprayed.
Also here is an exaple of the spotted blooms one gets around here if one doesn't spray. I don't see this in summer as the fungicide takes care of keeping the blooms clean.
