Question
 I grow roses in containers in the SF Bay Area.  With the climatic conditions prevalent in my 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 roses 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 be too much for established roses in containers, some of which are likely root bound. Do you have any experience or info on whether this product can safely be used at full strength for container roses?  Any other 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
The All-in-one, is a very good product, if is used right. I use it on my roses. But, there are many other things, that you must do, as well, to prevent mildew.
If your roses are root bound, they are not healthy. Either do a root pruning, and then plant in fresh soil, or pot up to a larger pot with fresh soil.
Take great care in pruning. This is very important. Carefully take off any infected parts. Shape the plants in the vase, taking out all of the limbs in the center, all of the old wood, and any small limbs. Leaving only 5 good, healthy, canes. This will give good air circulation, and a stronger plant. Clean your pruners after each plant, with alcohol, or bleach, so the disease does not spread. Dispose of the diseased, pruned branches carefully.

MOST IMPORTANT. . . Water very carefully. If your plants are allowed to dry too much, or are too wet, to the point that they are unhealthy, this is the most common cause of powdery mildew. A plant under stress, is not able to fend off the disease. Be careful not to splash water on the leaves. Keep the leaves as dry as possible.

You are right, about the Pacific coast climate, being another factor in the equation. Not much can be done about that. And since spraying with sulfur isn't an option, then the systemic is the only other choice.
Yes, apply the FULL dose. One cap full to each plant, (I use the granules)for full sized roses, every two weeks as long as they have new growth. "Read the label instructions" As soon as they begin to go dormant, stop the application. Work the granules into the top two inches of the soil, or for the liquid, add to water, per instruction. (There should be two inches of loose soil on top of the roots) Make sure it is applied evenly. Then, water in. It will take several, continuous applications, all summer, to see results. You will need to do this every year.

If you notice drooping new growth, with burnt leaves, then you have some damaged roots. Discontinue the application. Give the plant time to heal itself, before you continue.

bakerplanter