What is a good test for whether a daylily has hidden rust?
There is no quick test. A fairly safe, slow test would be to bag the plant in a plastic bag in the shade for several months, maintaining the temperature, moisture, and high humidity needed for spore production. The optimal conditions (heat, humidity, etc.) for revealing or concealing infection are not yet known. However, apparently fungicide applications and/or summer heat can conceal infections for months. This is possibly how rust recently evaded Australian quarantine.
