I'm pretty sure Aureobasidium microstictum is not an obligate parasite. I haven't had time to re-read the first research on it from Japan but I believe they were able to grow it in culture which would have pretty much ruled out its being an obligate parasite. A necrotrophic pathogen would be the opposite of a biotroph (and also that new Botrytis is considered to be a potential endophyte, just to complicate matters). If we're going with the term obligate parasite then the other categories would be facultative saprophyte, facultative parasite, and saprophyte (the latter is not disease causing). I believe Botrytis cinerea would be considered a facultative parasite. Nutrient effects on Botrytis species are described in the Datnoff book, there are several mentions in the index. If I have time in the next few days I'll look up which nutrients have an effect (although whether that would extrapolate to the new one on daylily I don't know).
Collecephalus hemerocalli is an old name for Aureobasidium microstictum. See the AHS daylily dictionary leaf streak page for other old names:
http://www.daylilies.org/ahs_d...
Myzus hemerocallis is not the only aphid species that affects daylilies, ditto for Frankliniella (not the only thrips genus that has been reported on daylilies). You can get more info on these also from the AHS daylily dictionary.
The bulb mite, Rhizoglyphus echinopus (also R. robini in my case), has been proposed as possibly involved in spring sickness, but has not been implicated in leaf streak. Having said that, anything that damages foliage, including weather, thrips and other pests etc. could potentially create an entry for the leaf streak fungus, which is believed to need some injury before it can infect the plant.
Summer dormancy is more likely related to drought and/or high temperatures I would say.
