Hi
@xenacrockett and
I have dipped bare root daylily plants in a weak hydrogen peroxide mix (about 10%) after dividing them with no ill effect before repotting or returning them to the garden. I don't know if hydrogen peroxide dipping stops fungus gnats on daylilies, but that is just because we don't seem to get them here.
For leaf insects, like aphids (which I do get), I use a spray bottle of mild dishwashing liquid that is mixed with water (also about 10%) on the foliage and it not only kills the nymph aphids but does seem to also "down" the flying insects around them. I do need to periodically re-spray to catch successive cycles of hatching aphids, but it is quick and easy to do and I do not have to wash off the mild soap from the foliage. I suspect the flying ones are adult aphids, rather than gnats, but might be worth a try for the fungus gnats if the hydrogen peroxide dip does not provide lasting protection?
Love your avatar picture - what daylily is that?