M.R. Ayres

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.

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.