I know AZ is not the place to test sprays that fight fungus, but I was surprised at how effective Green Cure (potassium bicarbonate) as a dip was on young roses with cercospora that rode in on new plants. So far except for that, I've spotted no spots of fungus of any kind on my roses.
Other sprays include Freeze-Pruf to prevent freeze damage - (which works especially well in the summer !), a magic repellant spray whose name I totally forget to stop furry nibblers from taking all the new foliage off roses, and Messenger to stimulate growth - once the foliage is old enough not to be very threatened by small animals.
Just read a book on growing big tomatoes and one champion grower advocates spraying with powdered milk. That made sense to me in context with another piece I read recently about cultivating friendly bacteria that gobble up or out-compete bad ones and fungi. It also acts as a foliar source for minerals for the tomatoes. Thinking of trying it on roses, too.
