For everyone, licensed or not, here is the FIFRA definitions page: TITLE 7 > CHAPTER 6 > SUBCHAPTER II > Sec. 136
Scroll down to the definitions for "pest" and "pesticide" and read and understand. Every state pesticide regulatory legislation I have read uses similar definition.
Now if you understand them, answer this question: If I find that my dog's urine kills dandelions, do I need a license to hire out my dog to kill weeds? In states I've checked, yes. BUT
, I can only use him if he has a legal pesticide label on him.
And for someone to use salt on lawns? Salt is more toxic to humans and most other life than most lawn care chemicals.