A few years ago there was an ongoing rust survey created by an AHS member and it was interesting to see how, for some cultivars, the ratings for them in different gardens varied. They could be all over the map for the same cultivar, resistant, susceptible, somewhere in between (there were five grades if I recall correctly). Some cultivars were more consistent. As Polymerous said, microclimates can make a big difference even within a garden, move a daylily from one spot to another and its apparent resistance/susceptibility changes. Now we also know there are different strains. Some can also take a lot longer to show any visible rust. So in the NGA database I would place more weight on a shows susceptibility rating than a shows resistance one, because low rust or lack of rust can merely be the result of environmental factors. In the NGA ratings anyone can come along and change shows susceptibility to shows resistance. On the AHS associated survey a cultivar was not shown on the list of rated cultivars until there were at least three reports from three different gardens. I'd rather it had been at least five but with so many daylily cultivars out there and everyone growing a different mix it would have meant very few cultivars were rated. Unfortunately due to technical issues the AHS-associated survey no longer exists.
