Organic Blackspot treatments
I found two organic ways to treat blackspot on roses...1 teaspoon baking soda, 1 quart warm water, few drops liquid soap spray in morning...the other is to mix a handfull of cornmeal into the soil at the base of question do they work and can I do both at the same time?
Submitted by ashfordheather

Hi, Well I've never heard of the cornmeal method, but doubt very much it would do anything. The other method might work, but I don't recommend mixing your own solutions because if you get the ration incorrect you can do more damage than good. Also, I don't know if it would work. I recommend two things for Black Spot. 1. Don't grow rose varieties that get the disease. There are many new varieties that have natural resistance. 2. Use a commercial rose fungicide. Black Spot is a fungicide so use a product that's designed professionally to combat the disease and follow label and application rates on the label.

Answered by doug.jimerson