The pyrethrum has worked great.
After initially soaking the top soil, I re-spray @ weekly. I have also moved to sunshine mix 70%, 30% potting mix, and the top 2" sunshine mix. I also put sunshine mix on the very bottom where the drain holes are.
98% better, and keeping a couple sticky traps out.
I still like a bit of potting soil in the mix. I keep reading about air at the roots and clear plastic cups.
In what I have known about growing, air is bad. It promotes fungus and disease, seeds, plants, and transplanting anything in the garden. On sensitive plants, the roots do not like light. They will brown and slow growth.
I do not see the need for clear cups as my success rate, other than the gnat plague, is well over 90%, roots and growth. I know some will not, but I'm starting to think my method or growing environment may be better, or people are too impatient or the cutting was not viable in the first place.
Most of my cuttings have been fresh, or having just gone dormant, and first year growth which I think helps too