Studies on the infestation by Eutypa lata of grapevine spring wounds

Natural infestation and controlled inoculations of grapevine (mostly on the cultivar 'Cabernet Sauvignon'), were conducted in Bordeaux vineyards from 1998 to 2004 to evaluate the susceptibility to E. lata of spring wounds caused by the removal of either excess buds or excess suckers. Natural infestation was assessed across a range of sites to quantify and compare the relative risk of spring and winter pruning wounds to contamination by E. lata . Infestation caused by inoculation of wounds was examined in one site using either 100 (lower inoculum density) or 1000 (higher inoculum density) ascospores per wound. Wounds were allowed to incubate at the wound site for either two weeks or one year before isolations. For natural colonisation of wounds, a low level of infestation of spring wounds (average 2.1 %) was detected, less than those for winter pruning wounds (average 13 %). A similar trend was detected in trials involving inoculation of spring and winter pruning wounds despite infestation with identical levels of inoculum. No difference in recovery rates of E. lata was found between spring wounds caused by the removal of buds or suckers. A longer incubation period significantly increased the mean efficiency of recovery. We conclude that spring wounds may pose a significant risk to the colonisation of grapevine by the pathogen E. lata , albeit less than that of winter pruning wounds, suggesting a secondary role in the epidemiology of Eutypa dieback.