Ascospores of grape powdery mildew (Erysiphe necator Schw.) play a crucial role in the disease onset in spring in many vine-growing areas. We investigated the physiological maturation of chasmothecia and the time of the first potential ascospore release in three grape-growing areas in Austria by providing standardized conditions for ascospore release in the laboratory and excluding the environmental influence for the release itself. In the overwintering season 2017/2018, the potential ascospore release started in March 2018 in all three investigated wine-growing areas, while in 2018/19, the potential ascospore release was already possible in autumn 2018. Autumn 2018 was characterized by higher temperatures than autumn 2017. We related accumulated degree days (base 8 °C) after chasmothecia formation with the time of first potential chasmothecia dehiscence and found that more than 480 degree days are necessary to reach physiological maturity of chasmothecia. Temperature significantly influenced the dynamics of the potential of ascospore release. More than 50% of the total potential of ascospore release occurred before bud break in both years. Furthermore, weather factors affecting the actual ascospore release in the field were studied. Precipitation and leaf wetness showed a significant positive correlation with ascospore release in the vineyard. In contrast to the potential release, only a small percentage of actual release in the field occurred before bud break, while 84 and 95% of total trapped ascospores were found between bud break and flowering in 2018 and 2019, respectively. Our results reveal that the potential release and actual release have to be combined to predict ascospore release in spring.

葡萄白粉病的子囊孢子（Erysiphe necator在许多葡萄藤生长地区的春季发病中起着至关重要的作用。我们通过为实验室中的子囊孢子释放提供标准化条件，并排除释放过程本身的环境影响，研究了奥地利的三个葡萄种植区的Chasmothecia的生理成熟和首次潜在的子囊孢子释放的时间。在2017/2018越冬季节，所有被调查的三个葡萄酒产区的潜在子囊孢子释放始于2018年3月，而2018/19的潜在子囊孢子释放已于2018年秋季开始.2018年秋季的特征是温度高于2017年秋季。我们将羊皮形成后的累积度数天（以8°C为基准）与首次潜在的羊皮形成性裂开的时间相关联，发现要达到羊皮形成的生理成熟度，需要超过480度日。温度显着影响了子囊孢子释放潜力的动力学。两年中，超过50％的子囊孢子释放潜能发生在芽破裂之前。此外，研究了影响田间实际孢子释放的天气因素。降水和叶片湿度与葡萄园中子囊孢子的释放呈显着正相关。与潜在释放相反，在田间实际释放的一小部分发生在芽破裂前，而在2018年和2019年之间，在芽破裂和开花之间发现了84％和95％的被捕获子囊孢子，分别。我们的结果表明潜在的释放和实际释放必须结合起来以预测春季子囊孢的释放。