We too have had an ongoing battle with scale in the Southern Tablelands NSW. We have used Eco Oil from Organic Crop Protectants with concentrated Garlic and Pybo (Pyrethrum) which seemed to be effective. However diligence is the key factor. You can only have success getting them in the wriggler stage so several sprays spaced about 2 weeks apart in sep/oct, dec/jan and feb/march could be necessary. We thought we had beaten the buggers this year but got a late outbreak in april. It's an onerous task which I think we will have forever. You can't beat them only minimalise them. Good luck.