Figure 1.

Effect of nutrient broth against powdery mildew on grapevine leaves under field conditions. Powdery mildew severity (A) and incidence (B) was assessed on leaves of grapevine plants treated with water (Control), nutrient broth (NB) or sulfur (Sulfur), as standard fungicide, under field conditions in three different seasons (2010, 2011, and 2013). Treatments were applied weekly from the beginning of May to the middle of August. Disease severity and incidence were assessed weekly as percentage of adaxial leaf area covered by white sporulation and percentage of leaves showing symptoms by scoring 40 leaves per replicate, respectively. The mean severity and incidence scores of three replicates (eight plants each) are presented for each treatment. The temperature and rain during the seasons were recorded by a meteorological station (C). The dosage of NB was 5.0 g/l in 2010, and was reduced to 3.0 g/l in 2011 and 2013 to avoid phytotoxicity.