Short-term Effects of Remedial Surgery to Restore Productivity to <em>Eutypa lata</em> Infected Vines

Abstract

Eutypa dieback, caused by the wood infecting fungus Eutypa lata, causes a gradual decline in vineyard production. Many growers renew infected vines by removing infected wood. Here we report on the short-term effects of the procedure on 28-year-old own-rooted Shiraz vines. In spring 1999, all vines in six adjacent rows were examined for foliar symptoms of Eutypa dieback. The following winter, cuts were made through both cordons and the trunk of each vine to determine the extent of wood discolouration, a symptom of E. lata infection. Foliar symptoms were recorded on 35% of the 141 vines, yet discoloured wood was observed in all cuts made through the cordons and in 71% of cuts made through the trunk. However, no association was found between the foliar symptoms observed in the spring prior to surgery and the extent of wood discolouration, i.e. discolouration that was visible on the cut surface of the trunk (P=0.20). Furthermore, discoloured wood remaining in the trunk had no effect on the production of watershoots (P=0.74), which were produced by 63% of vines in 2000. When re-examined in spring 2001 and 2002, watershoots were observed on 61 and 76% of vines respectively. As in the previous year, no association was observed between the discoloured wood remaining in the trunk and the production of watershoots (P=1.00 in 2001, P=0.21 in 2002). Foliar symptoms were not observed in 2000, 2001 nor in 2002. Infection with E. lata was confirmed by isolation of the pathogen from 92% of discoloured wood samples taken from 14 vines.