Karen
The University of Guelph trials found that 1% dishwashing detergent was effective in stopping spores developing on leaves but think a systemic spray is needed as well to kill the mycelium inside the leaf. However, stopping the spores and spread is nice if the infected leaves are removed by hand. I can't find the original place where I read about people using Dawn but it has been mentioned in a number of NGA threads about rust. I recall that they used the 'plain' Dawn and not some kind which is also anti-bacterial or something similarly distinguishing. We don't have Dawn dishwashing liquid here. But I know that Glen I has sprayed using a detergent.
I noticed that Botanical Gardens of Auckland NZ article said that the older leaves of CADE STEWART were susceptible. I guess one might despair and banish plants that get rust on the young leaves. In fact I have had some seedlings that got rust, die right back, but then revive and grow bigger. However, I think it makes plants vulnerable to die from other causes.
Frank. I love the 'mums.
