Sensitivity of Australian isolates of Plasmopara viticola to acylanaline fungicides

Abstract

A floating leaf disk technique was used to test the sensitivity of Australian isolates of Plasmopara viticola to 4 acylanaline fungicides, phosethyl-A1 and phosphorous acid. Sporulation of all 15 isolates was completely inhibited by 1 mg/L of metalaxyl. Benalaxyl, oxadixyl and ofurace at 10 mg/L and phosethyl-A1 and phosphorous acid at 100 mg/L also completely inhibited sporulation of each of the isolates tested for each fungicide. These results indicate that acylanaline insensitive isolates of P. viticola are either not present or are not widely distributed in grape growing areas of Australia. Cultures of selected P. viticola isolates have been established on tissue-cultured grapevines. Sporangia from these cultures can be used as standards for future fungicide sensitivity testing.