Phosphorous acid treatments control Phytophthora diseases in Australia1

Abstract

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.