Hello,

The best thing to do this fall to control black spot include good sanitation (pick up and dispose of any plant material infected with the fungus), proper pruning to ensure good air movement through the canopy.  
Be sure to disinfect pruners between cuttings.   Ethanol or isopropyl alcohol are ideal for sanitizing pruning equipment because blades can simply be wiped or dipped into disinfectant without a prolonged soak.  
In the spring water so that the length of time foliage remains wet is reduced. Use drip irrigation to reduce the length of time that foliage is wet.
When black spot severity is high, use fungicides to control. Fungicides will be most effective if used preventatively, since the pathogen is known to
change rapidly.  All fungicides work best if used preventatively, before pathogen infection. They will be less effective if infection is established and even less effective if infection is well established.  Please read and follow manufacture directions when using any fungicides.

Hope this information helps.

Thank you for using Ask Extension.

Pam
MSUE Master Gardener