The original daylily rust research that tested dishwashing liquid (probably lemon "flavour", agree not antimicrobial) used it at 1% which I think works out at more than two teaspoons per gallon (I did work it out somewhere in an ATP thread I think, don't remember where). Maybe better to dilute it by percent, especially if Australia is the same as here in Canada where a gallon is not the same as a US gallon. Does it work for rust at a lower concentration than 1% - don't know so it will be interesting to see your results Becky.
