Control of Cucumber Downy Mildew Using Resistant Cultivars and Organic Materials

Abstract

We selected eight resistant cultivars including 'Heukryongsamcheok', 'Heukgeumsolsamcheok' and 'Gangryeoksamcheok' showing high suppressive effect against cucumber downy mildew (CDM) through plastic film house and field trials in spring and autumn season in 2015. Of them, these three varieties, 'Heukryongsamcheok', 'Heukgeumsolsamcheok' and 'Gangryeoksamcheok' were used to evaluated suppressive effect against CDM by comparing disease severity (area under disease development progress curve, AUDPC) with those of three susceptible varieties under plastic film house condition. AUDPC of three resistant cultivars was in the range of 10.9 to 23.6, meanwhile those of three susceptible cultivars was in the range of 286.7 to 290.3. Consequently, we confirmed that cultivation of the selected resistant cultivars can reduce CDM in vivo. When disease severity (diseased leaf area) was investigated on a resistant cultivar ('Heukryongsamcheok') sprayed without any organic materials and susceptible cultivars sprayed single-, two times-and three times with Bordeaux mixture, sulfur-loess mixture and Kocide R (copper hydroxide), respectively, it was the lowest in the resistant cultivar plot compared to susceptible cultivar plots sprayed with any organic materials. In addition, we evaluated control effect of the selected resistant cultivar by comparing that of organic materials including lime sulfur mixture, Bordeaux mixture and garlic extract. As a result, Bordeaux mixture showed the highest control effect against CDM. AUDPC of Bordeaux mixture, resistant cultivar, lime sulfur, garlic extract and untreated control was 3.9, 10.6, 95.6, 24.9, and 258.7, respectively. Based on the above-mentioned results, we think that the resistant cultivars and Bordeaux mixture can be effectively used to control CDM as one of control measures under the farmhouse condition