CROP DISEASE CONTROL BY SPRAYING ELECTROLYZED STRONG ACID WATER IN PROTECTED CULTIVATION

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Effects were investigated of spraying electrolyzed strong acid water (ESAW ; pH : 2.8, free effective chlorine concentration (ECC) : 32 ppm, oxidation-reduction potential (ORP) : 1120 mV), which was obtained by electrolysis of a NaCl dilute water solution, on the incidence of powdery mildew and downy mildew on/in leaves of cucumber grown in a plastic house. Different amounts of the ESAW or well water were sprayd onto the leaves once every third or fourth day. The incidence of powdery mildew on cucumber leaves was significantly reduced on day 11 by spraying 1 and 2l of ESAW per plant compared with control (no spray) ; and spraying 4l of that compared with well water and control. The incidence of downy mildew was controlled for 25 days by spraying the ESAW regardless of the amount sprayd and was delayd more than 10 days against well water and more than 7 days against control. However, spraying the ESAW caused a leaf-burn-like physiological disorder in some leaves after day 15 and the per … More centage reached around 50% on day 25 regardless of the amount sprayd. These results indicate that ESAW can be used for controlling some crop diseases and can be then a viable alternative for some agricultural chemicals or be effective in reducing application amounts and/or frequencies of some agricultural chemicals although there remains the problem of a leaf-burn-like physiological disorder.Effects of spraying waters with different pHs and ECCs on the disease severity of powdery mildew and gray mold, and on the incidence of a leaf-burn-like physiological disorder were also investigated as a fundamental research to clarify the main factor controlling crop diseases by ESAW.pH-regulated water, ECC-regulated water, or distillled water was sprayd at intervals of 3 or 4 days on leaves of tomato grown in a plastic house. A statistical analysis of the results showed that main effects of pHs lower than 2.7 and ECC more than 20ppm were significant individually, and that there was a positive interaction between the two factors on the control of powdery mildew oll tomato leaves. However, there were no significant differences in the disease severity of gray mold among all the regulated waters sprayd and control. The leaf-burn-like physiological disorder was observed in some leaves with all the regulated waters with ECCs of more than 20 ppm or with pHs of less than 2.7. Less