Question
I was interested to read a recipe based on what was called baking soda. Being british I dont know if baking powder or bicarbonate of soda was meant!
Apparently 3 tsp of "baking soda in a bucket of water together with one tsp washing up liquid does the trick.
Can you clarify what ismeant by "baking soda" please?

Answer
Alas, if only it was that simple. Black spot fungal spores are in the air and when it rains, they fall onto the rose leaves and start their life cycle. Spraying the rose leaves with bicarbonate of soda just makes the leaves less attractive to the spores. The amount is 1 tablespoon of bicarbonate of soda to 1 quart of water. The washing liquid is just used as a sticker and really isn't necessary. This spray must be used before you see any evidence of the disease. Once it becomes mould or black spots, it is too late. Good success has been had by using a sulphur and dormant oil spray before the roses bud out. This kills any spores that have overwintered. If the roses have leafed out, then you can use the summer strength spray which will have the instructions on the package.