Grapevine Yellows, a Widespread, Apparently New Disease in Australia. P. A. Magarey, Department of Agriculture, Loxton, South Australia 5333. M. F. Wachtel, Department of Agriculture, Loxton, South Australia 5333. Plant Dis. 70:694. Accepted for publication 17 March 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-694d.
A yellows disease of Vitis vinifera L., first observed in 1975, occurs in all major viticultural regions of Australia. Symptoms are nearly identical to the disease flavescence dorée in France and include yellow and downward curled leaves that fall prematurely. Shoots are stunted and unlignified. Any time from flowering, bunches may shrivel and fall. Disease incidence is highest in the warmer, inland regions and on the cultivars Chardonnay and Riesling, although De Chaunac is also affected. Oxytetracycline hydrochloride (0.05 g a.i. per vine), pressure-injected into dormant vines, reduced the incidence of symptoms in the next year by 97% (P <0.001) and remained effective for five seasons. Doses as low as 0.005 g a.i. per vine also were effective (P <0.05), but penicillin (0.7 g a.i. per vine) was not. Phloem cells from symptomatic shoots and petioles fluoresced strongly with epifluorescent microscopy. Pathogenicity by a mycoplasmalike organism is suggested. Preliminary electron microscopy and graft transmission studies have been unsuccessful, but no other pathogen has been implicated. Further studies are needed to resolve etiology. The name “Australian grapevine yellows” is proposed for this newly reported member of the grapevine yellows group.