Really the only ingredient needed is the Sodium Laurel Sulfate, or
Sodium Laureth Sulfate.

These ingredients are foaming agents, also known as surfactants. They
basicly make water "wetter". Water will normally pool on or fall off
insects due to the waxy layer on the outside of their exoskeleton. A
surfactant will allow the water to completely cover the bug and
actually soak into its' spiracles. This essentially drowns the bug.

I'm not sure if you can find a surfactant anywhere, but let me forewarn
you, a little goes a looooooooong way. One teaspoon of the stuff I use
will turn 3 gallons of water into 25 gallons of very dry foam.

I don't believe that a surfactant will harm plants... but someone
inform us. I'm curious about this.