Question
I grow roses in containers in the SF Bay Area.  My biggest and most enduring problem is powdery mildew.  Last year I purchased Bayer's Advanced Garden All-in-One Rose & Flower Care (the systemic to be used as a soil drench, not the one to be used for spraying).  I diluted it to half the recommended strength and applied to two roses, with no discernable results (i.e., no damage to the rose but also no disease control), but it was late in the season. I want to apply full strength to all of the roses now, which is about a week or two before the usual onset of the mildew.  My concern is that the full strength may too much for established roses in containers, some of which are likely root bound.  Any suggestions/recommendations?  Spraying is out as it is too windy where I live and I am too close to my neighbors.  Thanks for any help.

Answer
As you know, mildew is caused by a climatic condition and because of that it lands on the rose leaves or anywhere else it can, and then the spores start to make mildew. I understand your problem of not spraying but the only way to get rid of the spores is to make sure they are totally covered with a solution and spraying is the only way to do that. Spraying a rose with 1 tablespoon of baking soda to a quart of water every 5 days, has proven to be very effective against mildew. You could even do it daily if needed without any damage. I know they say it is good for black spot too but alas it is not. Bayer products are not strong ones and people do report that they are not always effective because of that.If you are concerned then I would go to the next level of strength. The ingredient in it that would do any damage is the insecticide as his will be the strongest. Hope this helps.