Cultivar susceptibility and control of angular leaf scorch in grapevine

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.