Phosphorous acid treatments control Phytophthora diseases in Australia.

Treatments with a partially neutralized formulation of phosphorous acid containing potassium phosphite were assessed for control of Phytophthora diseases in subtropical and temperate crops in Australia. In Queensland, trunk injections of phosphite (10% solution) controlled severe root rot (Phytophthora cinnamomi) of avocado trees and resulted in the recovery of trees. Single pre-harvest sprays (2.5 kg ha-1) of phosphite controlled root and heart rot (P. cinnamomi) of pineapples. Foliar sprays of phosphite (64 g per tree) controlled root rot (P. nicotianae var. parasitica) and trunk canker (P. citrophthora) of mandarin trees. In Victoria, a foliar spray of phosphite (300 g ha-1) reduced root rot (P. clandestina) of subterranean clover and increased dry matter by 1.96 to 5.11 t ha-1. Trunk injections of phosphite (10% solution) controlled trunk rot (P. cactorum) of peach trees and foliar sprays (10 kg ha-1) reduced severity of root rot (P. nicotianae var. nicotianae) of tomatoes.