Spores from D. ampelina isolate Nita001 were produced according to Travadon et al. (2013) from an isolate originally collected in June 2015 from leaf spots on ‘Cabernet Sauvignon’ in Winchester, Virginia. The spore suspension was adjusted with sterile water to 1 × 106 conidia ml−1 and was sprayed until runoff on the leaves and stems of plants using an atomizer (Mondi Mist & Spray Deluxe Tank Sprayer, Hydroframs, USA). Non-inoculated plants were sprayed in the same way, but with sterile water instead. Infection was encouraged by covering each tray with a dome (XL High Dome Propagator, Garland Products, England), maintaining greenhouse conditions at 20 °C and continuous light for 24 h. After this 24-h wetting period, domes were removed from each tray.