4.2. Experimental Vineyards and Location

Five field trials were conducted from 2018 to 2020 with the powdery mildew susceptible grape cultivars: ‘Cabernet Sauvignon’ (trial 1; 2018), ‘Chardonnay’ (trials 2 and 3; 2019 ‘Riesling’ (trial 4; 2020), and ‘Carignan’ (trial 5; 2020). Vineyards were located in the Golan, Upper Galilee, and Judean foothills regions of Israel (Table 6). Field trails 1–3 and field trials 4 and 5 represent different research questions. The efficacy of the nutrients in field trials 1–3 were compared to highly effective synthetic reference fungicide (Abir) and to an effective commonly used organic product (Heliosulfur). In trials 4 and 5, the efficacy of mixtures of nutrient plus fungicide was tested compared to nutrients or fungicide alone. Therefore, in order to demonstrate the enhanced effect of adding nutrients to the mixture, in trials 4–5, we used Folicur, which is considered a fungicide with moderate effect against grape powdery mildew in Israel. In addition, resistant isolates of E. necator to Folicur were reported in Israel [100], therefore emphasizing the need for additional control measures against grape powdery mildew.

Field trials conducted to assess the efficacy of nutrients and fungicides against E. necator.

¹ Fertilizers were applied with the nonionic surfactant Triton X100 at 0.025%. ² Date of bloom: BBCH-61 = Beginning of flowering: 10% of flowerhoods fallen. ³ BBCH-13 = 3rd leaves unfolded, BBCH-15 = 5th leaves unfolded, BBCH-77 = Berries beginning to touch, BBCH-79 = Majority of berries touching. ⁴ TM = Tank Mixture. ⁵ Alt = Alternating applications of Top KP+ (1%) plus TruPhos (0.25%), Folicur (0.02%), Top KP+ (1%) plus TruPhos (0.25%), etc.