aSaid M. Kamel, bMohamed M.I. Afifi, aFathia S. El-shoraky, aMohamad M. El-Sawy( 2012). Fulvic Acid: A Tool For Controlling Powdery And Downy Mildews In Cucumber PlantsInt. J. Phytopathol. 03 (02) 2014. 101-108
Abstract: A greenhouse experiment was carried out on cucumber cultivar DP-164 during the seasons 2012-2013 to evaluate the efficacy of three concentrations of fulvic acid (FA) to control downy and powdery mildew diseases compared with the recommended fungicides and their effects on plant growth, chlorophyll content and yield of cucumber plants. Results revealed that all FA concentrations significantly reduced disease severity of both diseases. The highest reduction in disease severity of downy mildew was recorded using 75 ppm of FA, which was more effective than the recommended fungicide. The significant effect of inhibition of powdery mildew diseases increased gradually with increased FA concentration. At the same time, the reduction of diseases severity was greater than or equal to the recommended fungicides. Foliar application of FA concentrations and Ridomil fungicide increased significantly all morphological characters. Sumi-8 fungicide increased the morphological characters except plant height, dry weight/ plant and leaves number/ plant. The yield components (weight of fruits and mean of fruit weight /plant) recorded the same values with all FA concentrations. Fulvic acid had direct effect on soil microbiology by increasing plant exudates, which enhanced the activity of microorganism. Fulvic acid at 150ppm showed the highest increase in dehydrogenase and nitrogenase activity. This study revealed that the foliar application of FA improved plant growth and yield quantity and quality as well as controlling powdery and downy mildews of cucumber plants. Additionally, FA has the advantage as effective and environmental friendly agent.
Keywords: (Control, humic substance, Podosphaera fusca, Pseudoperonospora cubensis. )
