trouble rooting camellias
The trouble we are having is the cuttings drop leaves and die before rooting. We are in proper medium of sand/peat moss. The rootings die off by variety and the ones next to them are healthy. Strange how a certain variety drops leaves - does not callus but the ones next to them remain viable. We theorize that an systemic insectice (ie: cygon) may have been used.
Many volumes have been written and countless have been spent in honing the process of rooting woody ornamentals. There are as many theories and opinions of the process as there are people doing it. A lot of times, it's pure luck, sometimes, it is trial and error, but always success is a "good thing". I don't think an insecticide would have a great deal to do with root development.
Plant material, media, humidity, hormone and temperature are the 5 most important variables in woody propagation. This link might help: https://www.gardeningknowhow.com/garden-how-to/projects/rooting-plant-cuttings.htm