Question
About this time of the year my roses are beautiful and blooming. In about two weeks
my stems will start loosing their leaves.
They get black spots on them, turn yellow
and fall off.
 What is the cure for this and what caused
this.
                     Di

Answer
Good morning, Di,

After a fair amount of testing, I want to recommend an alternative to Baking Soda for your fungus problems on Roses: Potassium Bicarbonate.

Used just like Baking Soda as a fungicide, Potassium Bicarbonate is sold in formulas at several Organic Retailers including one called Greensense (www.greensense.net/pti.html).  I mention Greensense because they also have a very nice Rose food that is gentle and very nutritious.  

For your Roses, that is.  

I thought you might like to see it.  

Be cautious when applying in full sun.  Better to spray early in the morning to minimize any possible burn.