I have tried spraying stuff on leaves and I end up losing plants for it. I like a nice systemic. When I spray plants I try to make sure it is a very windy day. I do a foliar spray twice a month now, but I add a little fungicide in and again, it has to be a windy day. I have certain cattleya that totally despise their leaves wet and for those I don't mist them with anything even on a windy day.