Unless you have "grandfather rights" i.e. born before 31st december 1964, you are required to hold a Certificate of Competence for the application of pesticides.  NPTC is the awarding body for this and your certification starts with PA1 the Foundation Module called "Safe Handling of Chemicals".  This is followed by a practical application module like PA6 for Hand Held Application or PA2 for Tractor Mounted Application.