I use half strength dilute neems oil with a spoon of baking soda and a squirt of Dawn dish soap. It helps with aphids, but I am not sure if it helps black spot. I still had some last year, but less than the year before when I didn't spray. I always try fertilizer/sprays./whatever half strength and use them more often if needed. A couple of roses need something stronger this year.
Hope you continue to feel well, zuzu. I have asthma, triggered by mold or cigarette smoke, so I am also very careful with sprays. I majored in Chemical Engineering at Cornell, so I always research everything up before using it.
I wish I could grow lemon balm. I managed to get a few sad sprigs in a pot last year, but they didn't thrive.
