Are there any home-remedies for black spot on roses?

Answer 1

Here is a recipe that will work if you have caught it early on:
2tbs of cooking oil
2tbs of baking soda
mix well in one gallon of water

using a spray bottle mist all sides of leafs, besure and do this as all your watering early enough in the day that there will not be any moisture left on your plant by nightfall.
It is very important to remove any fallen leafs and debris around your plant, dispose of right away.
Remove (prune) as many infected leafs a practical
reduce the size of your bush, I usually would cut off the new blooms, by doing so you are giving your bush energy to heal instead of it using its energy to blossom.
You will need to spray every Day for a week to 10 days, and then weekly through out the season.
If it is possible remove the top layer of your soil, gently scraping as to not spread the dirt and dispose and replace with good fresh soil.
If you have caught it early enough this will work for you.
wish you well!
God Bless
Grandma

Answer 2

I spray them with daconil, its an anti-fungal you can get at home depot.
pull off any leaves that have spots on them and throw them in the trash, then spray the rest of the bushes.

Answer 3

poppy seeds