Search

Background and Aims: Eutypa and Botryosphaeria dieback are diseases that affect vineyards worldwide, reducing productivity and longevity. The ability of the causal pathogens Eutypa lata and Diplodia seriata to colonise grapevine canes was investigated in the search for resistance or tolerance to trunk diseases. Methods and Results: Visual assessments of 174 winegrape cultivars (Vitis vinifera) in a mature germplasm collection in the Barossa Valley in South Australia revealed substantial variation (0–98%) in severity of foliar symptoms and dieback. A selection of 18 cultivars representing those without symptoms or low (<10%) severity was compared with the susceptible cultivars Shiraz and Sauvignon Blanc. Inoculation of canes in situ in the vineyard and detached canes in the greenhouse, confirmed variability among cultivars for the extent of pathogen colonisation. Conclusions: Cultivars varied in susceptibility to colonisation by E. lata and D. seriata, with some differences between the two pathogens in terms of the ranking of cultivars. Muscadelle was most resistant to colonisation by both pathogens, and Sauvignonasse was the most susceptible. Significance of the Study: Knowledge of cultivar susceptibility to grapevine trunk diseases will assist in prioritisation of disease management strategies. Identification of cultivars with resistance could inform selection of planting material and may lead to improved breeding programs in the future. [ABSTRACT FROM AUTHOR]

Background and Aims: Angular leaf scorch (ALS), caused by the fungus Pseudopezicula tetraspora, is an exotic disease threat to the $45 billion Australian wine industry. Research was undertaken at the Cornell University New York State Agricultural Experiment Station in Geneva, NY, USA to develop contingency plans for the Australian wine industry in the event of an ALS incursion. Methods and Results: Evaluation of Vitis vinifera cultivars widely grown in Australia revealed that Riesling, Sauvignon Blanc, Cabernet Sauvignon and Pinot Noir have moderate to high susceptibility to infection by P. tetraspora. The fungicides trifloxystrobin, pyraclostrobin and tebuconazole were shown to be effective at controlling ALS. A drastic pruning eradication strategy was successfully validated for ALS, resulting in no disease recurrence within 3 years of the initial eradication protocol. Conclusions: Cultivars grown in Australia ranged in susceptibility to ALS. Fungicides available in Australia are effective and could be used to control ALS in the event of an incursion. The drastic pruning strategy will be included in the Australian Viticulture Industry Biosecurity Plan for potential implementation as part of an incursion response. Significance of the Study: This research contributes to the biosecurity capability of the Australian viticulture industry and to improved industry preparedness. It has the potential to reduce production losses and vineyard re‐establishment costs, while maintaining the competitive advantage conferred by freedom from exotic diseases. [ABSTRACT FROM AUTHOR]

Background and Aims: Grapevine trunk diseases, caused by fungal pathogens that infect pruning wounds, pose a major threat to the sustainability of vineyards throughout the world. Pruning wound protectants can control infection, but little is known about the optimal timing of application of protectants following pruning. In this study, the timing of fungicide application to pruning wounds was evaluated to assess curative and preventative effects. Methods and Results: To assess curative control, on the day of pruning, wounds were inoculated with ascospores of Eutypa lata or conidia of Neofusicoccum luteum followed 1, 3 or 6 days later by application of the fungicides tebuconazole, pyraclostrobin or fluazinam. To assess preventative control, fresh pruning wounds were treated with the same fungicides, then inoculated 1, 6 or 14 days later. The fungicides provided curative control of both pathogens for up to 6 days and preventative control of E. lata for up to 6 days and of N. luteum for up to 14 days. Conclusion: These results indicate that fungicides can provide control of trunk disease pathogens when applied up to 6 days after wound infection, and continue to protect wounds for up to 14 days after application. Significance of the Study: Current recommendations to protect grapevine pruning wounds from trunk disease pathogens are to apply protectants within 24 h of pruning. This study suggests that a single application of the fungicides tested 6 days after pruning may provide up to 3 weeks of wound protection, thereby offering improved flexibility in managing grapevine trunk disease. [ABSTRACT FROM AUTHOR]

Background and Aims: The trunk disease Eutypa dieback causes financial losses in grapegrowing. The influence of two pruning methods, namely cane and spur pruning, on the incidence and severity of Eutypa dieback in Shiraz grapevines was investigated as pruning wounds are a major point of entry for the causal agent Eutypa lata. Methods and Results: The surface area of pruning wounds in 11 Shiraz vineyards in the Barossa Valley was measured. The incidence of Eutypa dieback in all of those vineyards and disease severity in two vineyards were determined. The surface area of wounds exposed by cane pruning was 21–33% smaller than for spur pruning. The incidence of foliar symptoms and the severity of disease were 50 and 38% lower, respectively, in cane‐pruned than in spur‐pruned vines. For cane‐pruned vines, an increase in bud number retained was associated with a smaller increase in wound surface area than for spur‐pruned vines. Conclusions: The incidence and severity of Eutypa dieback were greatest where the total surface area was largest rather than the size of individual cuts exposed by pruning. Significance of the Study: Limiting the total surface area exposed by pruning in plantings of Shiraz vines is likely to reduce the incidence and severity of Eutypa dieback. [ABSTRACT FROM AUTHOR]