The spread of Eutypa lata within grapevines - implications for management of eutypa dieback

Abstract

Although the expression of foliar symptoms of eutypa dieback influenced by grapevine cultivar and isolates of *Eutypa lata*, there are no reports documenting their effect on the distribution of *E. lata* in grapevine wood. We developed a bioassay which allows rapid induction of the foliar symptoms of eutypa dieback in vines in a shadehouse. Here, we used the bioassay to assess the ability of different isolates of *E. lata* to induce foliar symptoms and colonise inoculated vines. This study revealed that the virulence of the pathogen varies among isolates of *E. lata* and the cultivar grapevine inoculated, and indicated that the severity of foliar symptoms may not be related to the rate of spread of the fungus in the vine. It also showed that the staining of wood typically associated with eutypa dieback may not correlate with the presence of the fungus, and that *E. lata* grows to 75 mm in advance of the stain. We also conducted a field trial to assess the spread and extent of staining induced by *E. lata* in mature vines of eight cultivars, which enabled comparison between young vines in the shadehouse and mature vines in the field. Information from this study will help to optimise management strategies for maintaining productivity of grapevines with eutypa dieback, thus reducing the economic impact of disease.