Q.sego palm
How can I make an Horticultural soap?
I’ve been treating my sego palm for about a year and it gets quite expensive.
I have now trimmed all the palms off. It has scale and the white residue.
Appreciate your help.
Paul

Here are some recipes for horticultural soap:
https://www.gardeningknowhow.com/plant-problems/pests/pesticides/homemade-soap-spray.htm
These articles will provide information about scale bugs on sago palms and other control methods:
https://www.gardeningknowhow.com/ornamental/trees/sago-palm/sago-palm-pests-and-disease.htm
http://edis.ifas.ufl.edu/in253
http://extentopubs.tamu.edu/eee_00038.html