Wash. Rev. Code § 15.58.240
The director may classify licenses to be issued under the provisions of this chapter. Such classifications may include but not be limited to agricultural crops, ornamentals, or noncrop land herbicides. If the licensee has a classified license the licensee shall be limited to practicing within these classifications. Each such classification shall be subject to separate testing procedures and requirements: PROVIDED, That no person shall be required to pay an additional license fee if the person desires to be licensed in one or all of the license classifications provided for by the director under the authority of this section. The director may charge examination fees established by the director by rule. The director may administer or contract with a public or private third-party entity to administer any or all parts of either the examination or the collection of examination fees, or both. Examinations administered by third-party entities must be the same as the examination that would otherwise be administered by the department. The department may direct that the applicant pay the fees to the third-party entity in accordance with department rules governing third-party examinations and fees. The director may renew any applicant's license under the classification for which the applicant is licensed, subject to reexamination or other recertification standards as determined by the director when deemed necessary because new knowledge or new classifications are required to carry out the responsibilities of the licensee.
RCW 15.58.240