Sawflies

Berberis and sawfly

Comment from William Robinson

It is my intension to plant a hedge using evergreen Berberis shrubs
unfortunately I already have a Purple Berberis bush that has become
infested with the Saw fly. Is anyone able to advise me: are Evergreen Berberis resistant to this pest; what do I need to do prior to planting the evergreen berberis aand how can I get rid of sawfly organicaly?