One more on fungus and I'll stop, I promise

We have had very bad infestations(?) of powdery mildew in the last two years. This stuff infects our dogwoods (very badly), magnolias, blackeyed susans, apples, mountain azaleas and many other plants I can't remember now. The dogwoods were so badly infected that the leaves drooped, turned prematurely yellow and dropped off the trees. I've been spraying with elemental sulphur the least toxic fungicide and the bonus is it also helps to acidify the soil. But I have to spray every week if it rains and it's a real chore to have to do that. Has anyone else had problems with this and what do you do to correct the situation? This year we've raked all the leaves around the affected plants and I will do pre-emergent spraying of the sulphur. If that doesn't work I'll try some of the oil sprays although I'm not very keen on doing so.

The darned thing is that almost all the affected plants are in full sun and not densely planted so they get lots of air and are not in dampish conditions at all.