Observations on some pythiaceous fungi associated with grapevine decline in South Australia

Abstract

A grapevine decline that causes considerable loss in grape production in South Australia was studied over a 2-year period. Isolations from soil and roots yielded various Pythium spp., mainly P. ultitnum, P. irregulare, and P. aphanidermatum. Five Pythium spp. were pathogenic to young grapevines in a glasshouse test. In thc field, however, disease incidence was not correlated with numbers of Pythium propagules in soil. Other soil fungi and root-feeding nematodes are also present, and it is suggested that the grapevine decline should be considered as a disease complex.