Question
I live in Baltimore, MD, zone 6/7.  I've just pruned my knockout roses, and found alot of blackspots on the canes.  Some of them had small circles of brown in the center, a powdery substance.  Last spring they had small caterpillars.  Didn't notice black spot last year. Are these treatable? Thank you.

Answer
What you are seeing is the black spot spores which have overwintered on the rose canes. Usually you see this fungal problem on the leaves but you can also see it on the canes. Because it is on the canes, any leaves that have fallen on the ground will also have the fungus spores too. I would clean up all the leaves and burn them as that is the only way you can get rid of the problem when it has overwintered on the leaves. In regards to the canes, any fungicide for rose black spot, such as Funginex, will solve your problem for you. Just follow the directions on the label.