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.

Sounds interesting, Patricia, can you please tell us the recipe? ie what proportion in a gallon of water. Also, what is chitosan, and where do you get it? I couldn't find it in a search as regards gardening, it seems to be some sort of medical supplement. Also, where do you get the potassium bicarbonate? Thanks!!

ParisRoseLady said: Sounds interesting, Patricia, can you please tell us the recipe? ie what proportion in a gallon of water. Also, what is chitosan, and where do you get it? I couldn't find it in a search as regards gardening, it seems to be some sort of medical supplement. Also, where do you get the potassium bicarbonate? Thanks!!

Got both chitosan and PB online, they are food grade. I guess some people take these for some reason.
Here is the chitosan.........................
https://www.amazon.com/dp/B01MTO38EL/

Potassium Bicarbonate link:

https://www.amazon.com/dp/B01MTO38EL/

Claire, I use only a quart of water because I don't have that many roses. I use one teaspoon PB to half teaspoon chitosan and just a squirt or two of Dawn dish liquid...mix by swirling around and it's ready to go. So, for a gallon, times four. I was amazed at how well it worked when I did my experiment with it. Next spring I'll use it through the entire warm season because this area is black spot alley.

Here is the way I found out this info. A rose nursery in Canada has cool, informative videos concerning roses and gardening in general. And he does give the ratios for a gallon which may be more correct than mine.

I have tried to change the links to the proper sites several times and they keep coming up as the chitosan. I'll put the video on another post because something is wrong with this post.

Patricia, all your links go to the Amazon chitosan listing, I think you cut and pasted the same one?!

ParisRoseLady said: Patricia, all your links go to the Amazon chitosan listing, I think you cut and pasted the same one?!

Oops. So sorry. BTW, here is what chitosan is.
https://www.webmd.com/vitamins...

Try this one...............

https://www.amazon.com/potassi...

Here is the link ( I hope ) for the video that explains about the above mixture and how to use it.

https://www.youtube.com/watch?...

LittleAnnie said: Oops. So sorry. BTW, here is what chitosan is.
https://www.webmd.com/vitamins...

Try this one...............

https://www.amazon.com/potassi...

I got the food grade of both of these simply because I thought it must be cleaner than the garden versions. They work.

Here is the link how to use it, from min 5:

https://www.youtube.com/watch?...

Patricia, thank you! It might be interesting how it works in rainy season.

Elena999 said: Here is the link how to use it, from min 5:

https://www.youtube.com/watch?...

Patricia, thank you! It might be interesting how it works in rainy season.

You're welcome, Elena. I hope it works for those who try it like it did for me. I went from no BS to lots of it when I switched to the other fungicides and I switched on purpose to see if it was really helping or if the lack of black spot was because of the Canadian fires making the air too polluted for fungal diseases.