There are three systems for registering pesticides in Pakistan - Form 17, Form 16, and Form 1. Form 17 allows registration of new pesticides without trials, while Form 16 allows registration of certain pre-approved pesticides without trials. Form 1 requires trials and is the only system that allows registration of any pesticide. The document outlines the requirements and process for registration under each form. Registration certificates must be renewed every three years by submitting the prescribed form and payment of fees.