Powdery mildew is that annoying white fuzzy fungal pest that affects rose gardeners everywhere. Constant vigilance is necessary to deter this annoying foe from your rose garden. Don't fear, there are a variety of ways you can keep powdery mildew under control.
Many garden plants can actually be affected by powdery mildew, not just roses. The control methods I've listed work for all garden plants, so feel free to use these tips on everything from your crepe myrtles to your roses. The first step is to select disease resistant plants. If you choose a rose that is resistant to powdery mildew to begin with your chances of encountering this fungus will be greatly reduced.
The next step is to plant your roses in full sun. Roses need at least 6-8 hours of full sun each day, preferably morning sun. Planting your roses in a partial sun area or an area without full sun is only asking for powdery mildew as well as a ton of other disease issues.
Your roses should also have plenty of air circulation around each plant. At the time of planting be sure to consider the full size of the roses you're planting as well as the ones in the garden that haven't yet reached their mature size. Nothing is more annoying than having roses so close together that they're not only hard to prune, but are also unable to keep their leaves dry since they're shading each other out.
You should try not to fertilize excessively. Powdery mildew prefers to grow mainly on new tender growth. If you encourage too much new growth you'll only be giving the powdery mildew more of it's favorite snack.
After you've completed the above steps and you're still having a powdery mildew issue, you should first try and trim off as much of the effected plant as possible without causing damage to your rose. Next choose either an organic or chemical fungicide to treat your roses with. Whatever you use to treat black spot also usually works on powdery mildew. If you would like to make your own spray, add one or two tablespoons of baking soda to one gallon of water and then the amount of insecticidal soap recommended on the label for one gallon of spray.
Your roses will need to be examined and sprayed once every one to two weeks until your problem seems to be under control. Vigilance is the key for controlling powdery mildew. Powdery mildew can overwinter on your plants so a true cure is often difficult to find.
Your best bet for future powdery mildew control is to select disease resistant roses. Then ensure they get the full morning sun they need. If you follow those two rules you should never suffer the death of a rose from powdery mildew.

