Powdery mildew on roses

I'm not sure whether it's mildew or possibly red spider but both are caused by dryness at the root, especially in hot weather. Also, remove and destroy any infected leaves that drop off. Hope this helps

I'm afraid the organic method is not all that effective against this fungal problem. It's also very contagious! Since your plants are miniature I wonder if they are indoors and possibly infecting other plants. The fungus loves dry soil and moist air. If you change these conditions you will make the conditions less conducive for the fungus. Remove infected leaves.

The best general rose spray is called Roseclear3 but you will need to use it regularly through the summer. It's very good against rust but it also contains chemicals which whitefly loathe so you could use it against these and it will be more effective than many of the so-called white fly killers.

Hi Andrewr: you're right it might possibly be red spiders, I saw some of them last summer...I do remove the infected leaves and try to increase circulation of air...do you think watering more would help?

Hi Muddywellies: It is very contagious, even though I have separated all my roses now...I used to have them all together which made the problem worse...they're outside, and I try to keep the soil moist but it's difficult with the Houston climate...I might succumb and try Roseclear3 if I can find it here, but I'd rather try something organic, yup, I know it might not be possible, but...a dream is a dream. No wonder it's so prevalent now, it gets hot during the day, but at night it cools off quite a bit, and of course the air is moist...this is a city where 80-90% humidity is not uncommon! Thanks for the advice.