Question
What is the best way to control or eliminate black spot on my roses without using chemicals? I heard/read that baking soda may help prevent it but... too late, my roses already have it.

Answer
I would use a systemic fingicide to rid the roses of leaf spots. Yes it is a "chemical" but so is baking soda. You can also try liquid sulfur-it is great for preventing leaf spots and should also control them depending on the extent of the problem. Try the sulfur first and if that does not help use the fungicide to control and the sulfur to prevent.