A simple method for application of phosphorous acid to control Phytophthora diseases was developed. The proposed method involves measuring equal weight of phosphorous acid and potassium hydroxide and dissolving phosphorous acid in water before adding potassium hydroxide. The pH of the neutralized phosphorous acid solution (NPA) is 6.2-6.7. The NPA concentration at 5000 mg/L was effective in controlling tomato seedling blight caused by Phytophthora capsici when using soil drench method. For suppression of lily leaf and blossom blight caused by Phytophthora parasitica foliar application is much more effective than soil drench. However NPA concentrations exceeding 2000 mg/L were phytotoxic to young plant tissues. The best results were achieved by applying NPA at the rate of 1000 mg/L for 3 times at one week intervals. Applying NPA to mother lily plants also effectevely protected bulblets from infection by P. parasitica during storage periods.
Full Text