Submitted to: Southern Nursery Association Research Conference
Publication Type: Proceedings
Publication Acceptance Date: 6/1/2001
Publication Date: 6/1/2002
Citation: Copes, W.E. 2002. Influence of select inorganic elements and ph on the fungicidal activity of chlorine dioxide in water. Southern Nursery Association Research Conference Proceedings. 46:282-284 Interpretive Summary: Ornamental plant producers need disinfectants to prevent the spread of disease through recycled water. Many of the disinfectants commonly used to treat benches and tools would damage plants if used to treat irrigation water. Chlorine dioxide is a disinfectant that has potential for treating large quantities of irrigation water in ornamental plant production systems. This study showed pH, water hardness, and nutrient leachates may dilute the effectiveness of chlorine dioxide. Rates needed to overcome these negative effects were determined. This information will lead to further studies and should be beneficial to other scientist, extension agents, ornamental plant producers, and any plant commodity group that will use chlorine dioxide.
Technical Abstract: Chlorine dioxide (ClO2) can be used to control pathogen propagules in irrigation water and on production surfaces wetted within a sprinkler zone. To determine to what degree soluble inorganic ions and pH of water can effect ClO2 activity, various concentrations of ClO2 were mixed with various concentrations of ammonium (NH4), nitrate (NO3), copper (Cu), iron (Fe), manganese (Mn), zinc (Zn), and synthetic hard water (sHW) at different pH levels. After 10 minutes of mixing, spores of Botrytis cinerea, Fusarium oxysporum, and Thielaviopsis basicola were exposed to resultant ClO2 doses for 30 seconds; then suspensions poured through filter paper disks. Disks were flushed with water and plated on 50 percent potato dextrose agar. Germination was quantified at 1 and 3 days. Water amendments significantly affected ClO2 activity similarly for all species. ClO2 activity was unaffected by NH4, NO3, Cu, Zn, and pH 4; slightly reduced by pH levels 5 to 6; moderately reduced by Fe and sHW, and pH levels 7 to 8; highly reduced by Mn; and severely reduced by pH 9 and 10. However, the lethal dose of ClO2 differed by species and propagule type. Ranges of 1 to 9 ug ClO2/ml water were needed to kill greater than 95 percent of conidia of F. oxysporum f. sp. narcissi and endoconidia of C. basicola, 5 to 20 ug/ml to kill conidia of B. cinerea, and 46 to 70 ug/ml to kill aleuriospores of T. basicola. Probit analysis was used to predicted dose and fiducial limits to achieve 95 percent mortality dependent on concentrations of independent variables.