@8700ft ...
Hi, 8700ft

Welcome to NGA.
I don't post often due to health issues.
My primary point was that a solution that works in one climate does not work in all climates.
In general, any product that contains any type of oil or fat leaves a residue on the leaf surface which in a hot and arid climate like mine, leads to burnt foliage because it cannot be washed off.
I am not a chemist, but did a little bit of research to respond to your post and am providing some links that may give you some better information.
Ingredients for castile soap:
Authentic castile soap is made of plant oils — coconut, hemp, sunflower seed, jojoba and olive. (Avoid brands with palm oil. That's devastating forests overseas where orangutans live.) Oils are mixed with an alkali — sodium hydroxide for solid soap and potassium hydroxide for liquid.
https://davidsuzuki.org/queen-...
Insecticidal soaps:
Soaps are made when the fatty acid portion of either plant or animal oils are joined with a strong alkali. They are potassium salts of fatty acids.
https://hgic.clemson.edu/facts...
Good article on insecticidal soap:
https://www.thespruce.com/how-...
Smiles,
Lyn