Where to buy mancozeb? And use frequency

Insects & Diseases
1

I have one rose plant (of 8) with black spot. The rose is over 100 years old and we want to keep it as healthy as possible. A nursery told us today to use mancozeb, then a week later Propiconazole, repeat the two steps one more round a week apart, then half strength propiconazole every 3 weeks.

  1. does this sound right?

  2. I can’t find anything but 6pound bags of dry mancozeb. Where do you all find it? No where local comes up in searches (around Nashville, TN)