Question
Hi
I read one of the other questions about fine white powder-looking stuff on mini roses and I have the same thing on my outdoor mini roses. I understand it is a fungal infection; my question is what will happen to the plant if left untreated?
Thank you
MJ

Answer
The disease is powdery mildew and if left untreated it will reduce the flower quality greatly.  Over years, it will weaken the plant until it just barely survives.  Use the one tablespoon baking soda and one tablespoon cooking oil in a gallon of water and treat the plants every 4-5 days.  This should help a lot.  Good Luck.