This document discusses phosphonate injection for controlling Phytophthora cinnamomi (Pc) in avocado trees. It provides details on: 1) The development of phosphonate injection technology in the 1980s. 2) How injection protects roots by accumulating phosphonate which controls Pc invasion. 3) Recommendations that February/March is the best time for a single annual injection in New Zealand to achieve over 6 months of root protection.