If the insecticide passes this test, then I feel comfortable using it on the rest of my plants. Daylilies are a relatively disease free plant. Crown rot is the only daylily disease that I have had to deal with here in the Salt Lake area. This disease is limited primarily to the deep south and usually only affects a small number of my plants. However, it can kill a daylily in a matter of only a few days.
Daylilies multiply by sending up new fans right next to the old fans.
Dig up the entire clump and shake off the dirt. A garden fork works well for this. Separate the plants by either pulling them apart or cutting into individual plants with scissors or knife. When cutting apart a large root with more than one fan growing out of it, try and include an equal amount of root with each fan. Yes, I usually do.