Studies on the effect of water and temperature stress on grapevines inoculated with Eutypa lata

Three independent studies were conducted in Australia and Spain to examine the effect of water and temperature stress on the development of Eutypa dieback in grapevines. In Adelaide, South Australia, 'Red Grenache' vines in pots were inoculated with Eutypa lata and subjected to various temperature and soil water regimes, then assessed for foliar symptoms, wood staining and colonization by the fungus. Vines subjected to a combination of heat or cold plus low or high soil moisture displayed more severe foliar symptoms, the most severe occurring on vines subjected to the hottest (30°C) and wettest (20–40% soil water content) conditions. Wood staining was not related to foliar symptom severity or to the temperature and moisture combination. Furthermore, there was no relationship between staining and mycelial growth, indicating that staining may not be an accurate reflection of the spread of E. lata. In Cabrils, Spain, 'Tempranillo' vines were subjected to water stress in pots and showed a significant reduction in shoot diameter growth, stomatal conductance and leaf water potential. Inoculation with E. lata also decreased the leaf water potential of stressed vines. Wood staining in inoculated vines was similar irrespective of watering treatment. Further investigations are needed to elucidate the relationship between stress and growth of E. lata in infected vines. Field experiments in two climatically different regions (Barossa Valley and Riverland) of South Australia suggested that water-stressed vines in a warm, dry environment may be more susceptible to infection of pruning wounds by E. lata than vines receiving standard watering.