Phytotoxicity of Phosphonic (Phosphorous) Acid and Fosetyl-Al to the Host in Mycorrhizal Cultures on Maize

Phosphorous acid (0.1 g/pot) and fosetyl aluminium (0.148 g/ pot) applied as soil drenches before planting to control Pythium myriotylum in vesicular arbuscular mycorrhizal (VAM) cultures on maize decreased top DW and mycorrhizal root length. Percentage mycorrhizal root length was not significantly reduced indicating phytotoxicity but not fungitoxicity of the chemicals to VAM. Treated plants were stunted and rosetted with white, variegated streaking of the leaves symptomatic of phosphonate injury. Metalaxyl (0. 0125 g/pot as a soil drench or 0.0188 g/pot as granules) did not adversely affect plant growth or mycorrhizal root length and as a result metalaxyl granules are routinely used to inhibit Pythium contamination of the mycorrhizal cultures. This paper was presented at the Phosphonic (phosphorous) acid workshop held at the University of Queensland, Brisbane, Australia, on 3 Jul., 1989. Australasian Plant Pathology 19(4) 141 - 142 Full text doi:10.1071/APP9900141 © CSIRO 1990