Final answer:
Private applicators generally must retake exams every three years to maintain certification, with regulations varying by state in line with federal guidelines.
Step-by-step explanation:
After obtaining initial certification, private applicators must retake exams every three years to maintain certification, which is generally true. Certification requirements, including the frequency of examination, are primarily regulated by individual states in accordance with the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) administered by the Environmental Protection Agency (EPA). Though there may be some variation in how often certification must be renewed, most states require private applicators to participate in continuing education and re-examinations regularly to ensure compliance with updated regulations and safe application practices.