There are several good recipes for powdery mildew here and on the web. There's a good one that I have used on Garden Web that you can find just by searching which is baking soda, dish soap and water.

I bought a couple of roses from Rite Aid around Mother's Day. They both had powdery mildew so when I got them home I star washing them with water, used the baking soda mixture referenced above, transplanted them into bigger pots with good sun and air circulation and the problem went away in short order.

Then again some roses are PM magnets. I might be chucking one of my new ones this year soon for that reason. But I'm sure someone will chime in with the exact recipe you need to try and fight it.

Hope this helps.

Kate

Hi Julie, lots of roses have powdery mildew in spring, it clears up when summer arrives (and I think it arrived this week!). The milk/water solution works well but you need to reapply after rain. Washing the foliage is good too, in the morning give your rose a bath with the garden hose to remove fungal spores then after it drip dries a bit treat it with the milk again. I wouldn't use the dish soap recipe now because the weather is too hot (I know folks who've burned the foliage with dish soap, you only need maybe a drop of soap and they add too much).