I couldn't resist buying three miniature roses from WalMart in early February. The two white ones have a lot of white, powdery stuff on the leaves; the red one has some. From reading several threads on powdery mildew from this forum, I bought a fungicide. My question is, can I spray the plants outside and bring them back in?

I have them indoors and am hoping to keep them alive and well until spring when I plan to plant them outside. I cut the blossoms off when dry and they both have a lot of new growth coming out. I really want to save these pretty ones!