Control of phytophthora root rot of avocado with phosphorus acid

Abstract

Phytophthora root rot of avocado and Persea indica caused by Phytophthora cinnamomi was controlled by spraying or drenching with phosphorous acid Dartiallv neutralised with potassium hydroxide, or with phosethyl Al. Phosphoric acid drenches increased phytophthora root rot in avocado, whereas dolomitic limestone, gypsum or diammonium phosphate did not affect disease incidence. A twenty per cent solution of partially neutralised phosphorous acid when injected into the trunks of seven-year-old trees affected by phytophthora root rot permitted rapid recovery of trees over a 12 month period. Injections with phosethyl Al (Experimental formulation 2008), and a ten per cent solution of phosphorous acid, and soil applications of metalaxyl gave slower remission of disease symptoms.