Hi Ya'll. I planted my new roses in early May and started a regime of spraying every two weeks with a mixture of potassium bicarbonate ( works much better than baking soda ) mixed with chitosan and dish soap. I did this for over two months and had no black spot at all on plants that tend to get black spot. Then I stopped and wow, the BS came on, especially, on Jacqueline du pre and Firefighter.
I wanted to pass this info on to all of you who battle black spot, mildew ( had none this year ) as a mixture that really works. I stopped spraying in early August ( on purpose ) and did spray with copper spray or baking soda mixture, which, did little to prevent disease. As you can see the first mixture worked far better.
Hope this is helpful to you rose lovers.
