Mo. Rev. Stat. § 281.080: Exemptions.

The provisions of sections 281.010 to 281.115 relating to licenses and requirements for their issuance shall not apply to:

(1) Veterinarians using pesticides on animals during the normal course of veterinary practice, as long as he is not regularly engaged in the business of using pesticides for hire amounting to a principal or regular occupation or does not publicly hold himself out as a pesticide applicator;

(2) Doctors of medicine or doctors of osteopathy using or prescribing pesticides in the practice of medicine;

(3) Government and private research personnel using pesticides under laboratory type conditions.