I think there is more than one cleaning product called "Green Magic". If you want to know what's in this particular one you could ask the specific seller for the MSDS (Material Safety Data Sheet). As has been mentioned before, diluted dish soap was also relatively effective against daylily rust in a study:
http://www.uoguelph.ca/%7Ethsi...
I don't know how the costs of supermarket dish soap versus "Green Magic" compare per treatment. In the study above the dish soap results are shown in comparison with conventional fungicides.
