Effects of Potassium Silicate in Controlling Powdery Mildew and Downy Mildew of Japanese Cucumber under Plastic House and Farmer’s Field Conditions

Abstract

This experiment had its objectives in testing the efficiency of potassium silicate for controlling of powdery mildew and downy mildew under plastic house condition and farmer’s field condition. The test for spraying frequency of potassium silicate in controlling powdery mildew and downy mildew under plastic house condition were done in Japanese cucumber cv. Pretty swallow 279 by comprising of spraying frequency at once a week and twice a week. Analysis of percent disease index (% DI) were done in data collection after transplanting for 6 weeks. It was found that the spraying frequency at once a week and twice a week gave non significantly difference in percent disease index. Both of spraying frequencies could greatly reduce the percent disease index when compared with pain water spraying as control treatment in both powdery mildew and downy mildew trials. The disease index in the spraying frequency at once a week, twice a week and control treatment were 51.9, 48.4 and 64.6%, respectively for downy mildew, and 39.6, 35.9 and 57.3%, respectively for powdery mildew. The marketable yields of cv. Pretty swallow 279 were increased with significantly difference in both spraying frequencies when compared with control treatment. There was no significantly difference for the yields in the spraying frequency at once a week compared with spraying frequency at twice a week. Marketable yields in the spraying frequency at once a week, twice a week and control treatment were 6.8, 6.5 and 4.9 Kg/ Sq.m., respectively. The test under farmer’s filed condition comprised of 3 treatments i.e. 1. fungicides alternated with bio-fungicide (Bacillus subtilis) 2. potassium silicate  alternated with fungicides and bio-fungicide 3. potassium silicate entire growing season. It was found that all of the treatments gave non significantly different results in both percent disease index and marketable yields. The percent disease index in the treatment 1, 2 and 3 at 5 weeks after transplanting were 41.5, 35.9 and 43.5 %, respectively. The marketable yield of cv. Robato in the treatment 1, 2 and 3 were 8.5, 8.2 และ 7.9 Kg/ Sq.m., respectively. Potassium silicate could reduce fungicide spraying frequencies for downy mildew in farmer’s field condition