From AHS FAQ:
Crown and Root Rots
Plant yellows and may collapse, leaves may pull out easily, affected tissue is often mushy and plant may die. Signs of a fungus may be visible, e.g. "shoestrings" for Armillaria rot, and "mustard seeds" for southern blight (Sclerotium rolfsii), otherwise exact diagnosis requires submission to a diagnostic laboratory
Foul smell may, or may not, be present
May involve a combination of factors such as nematodes, bulb mite or other pest damage, fungal and/or bacterial pathogens (disease causing agents), weather conditions, gardening practices, soil aeration and moisture conditions
Some cultivars may be more susceptible than others
Of particular concern in warmer climates but may also occur elsewhere
Ensure adequate soil aeration and drainage
Avoid or correct areas of poor air circulation
Avoid too much or too little water and don't over-estimate water needs in periods of high humidity (check soil moisture before watering)
Avoid over-fertilizing-Avoid over-amending with high water-retentive organic materials
Remember that high temperatures increase transplanting stress and try to avoid if possible
Don't plant too deep
Let wounds from dividing air-dry in the shade before re-planting
Remember that plants in pots are subject to more extreme root/crown temperatures (and therefore stress) than those in the ground
Treatment differs according to causative agent/s so get laboratory diagnosis of persistent rot problem
https://daylilies.org/daylilie...
To that last part, where a fungus is involved you need to know which one because different fungicides are appropriate for different pathogens. Thus what works for one person may not work for another.
