Question
Is powdery mildew curable?  We have used fungicides, Plant Sheild, Cease, etc.  We thought we were rid of it but it comes back every Spring with a vengeance.  We even had an Arborist spray.  It has spread to two large trees (Chitalpas) & almost every rose  (have about 150 of different varieties) in our one acre park-like yard.  I am afraid we will lose our entire new landscaped yard.  It was re-landscaped about two years ago (at great expense).  Should we tear all the roses out?!?  If we do that & plant new ones, will the new ones just get it too?  I'm at my wits end!  I'm hoping you will help.

Answer
Dear Dee Dee, I am so glad that you asked me this question because I can definitely help you.  True, powdery mildew is a fungus, but I've never had much luck using just fungicides on this either.  Your absolute best bet is to spray with a horticultural oil (SunSpray is my favorite and it comes in a convenient handy bottle that attaches to your hose.)  Spray the entire plants with the SunSpray on a sunny day and within a few hours the oil will dry and cause the powdery mildew to start flaking off.  Now since you have such a bad problem, you might want to add some fungicide to the oil. (You can spray them together.)  The recommended fungicides for powdery mildew will contain funginex, benomyl, or triforine, although there may be newer formulas, but they should specify powdery mildew and roses.  Now, also be sure to avoid getting the leaves wet during the day.  I am assuming with your landscape description that you probably have a sprinkler system, so set the watering to early morning to avoid keeping the foliage wet.  DO NOT water at night as the leaves will stay damp overnight and the mildew loves that.  One other thing is to keep a watch for aphids and other pests as they will transmit the fungus.  I am positive that you will have success.  Spray once a week for several weeks, and please write me back if you have any concerns or additional problems with this.  I absolutely adore roses and I can't stand the thought of so many beautiful roses not blooming and making us happy.  Now just to warn you, it will keep trying to come back because you have a lot of the fungus in your area, but you will now be able to stay one step ahead of it. Good luck, Melissa