Submitted to: Plant Health Progress
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/11/2003
Publication Date: 3/11/2003
Citation: Copes, W.E., Chastagner, G.A., Hummel, R.L. 2003. Toxicity responses of herbaceous and woody ornamental plants to chlorine and hydrogen dioxides. Plant Health Progress. dol:1094/PHP-2003-0311-01-RS. Interpretive Summary: Hydrogen dioxide and chlorine dioxide are disinfectants registered for certain horticultural applications. Information about effective rates and strategies that would allow these disinfectants to be used to control pathogens on ornamental plants is limited. This study used different rates of these disinfectants believed to be effective for disease control to see if damage occurred on various ornamental plant species. Rates of hydrogen and chlorine dioxides that should control disease causing organisms did not damage most of the plant species tested. These results provide meaningful parameters that will allow research scientist to develop efficacy and spray strategies for these disinfectants. The use of these disinfectants in this manner will minimize use of fungicides while improving disease control.
Technical Abstract: To determine potential phytotoxicity problems associated with foliar applications, chlorine dioxide (ClO2), at 0, 5, 50, 100, and 1,000 ppm, and hydrogen dioxide (H2O2), at 0, 900, 2,700, 5,400, and 10,200 ppm, were sprayed five times at 3 day intervals on eight bedding plant and nine shrub species. Injury to leaves and flowers were rated using Horsfall-Barrett categories, with marketability being reduced if > 5 % surface area was affected. Mean ratings > 5% occurred with ClO2 at 5 and 20 ppm on none of the plants after 5 sprays; at 50 ppm on poppy after 4 sprays; at 100 ppm ClO2 on pansy after 3 sprays, on azalea, mountain laurel, and poppy after 4 sprays, and on a fern after 5 sprays; and at 1,000 ppm on all plants, including coleus, evolvulus, galium, English ivy, juniper, lilac, rhododendron and St. Johns-wort after 1 to 2 sprays. Mean ratings > 5% occurred with H2O2 at 900 ppm on coleus after 4 sprays; at 2,700 ppm on rhododendron leaves and candytuft flowers after 5 sprays; and at 5,400 and 10,200 ppm on the coleus, rhododendron and candytuft in fewer sprays. Rates of 5 and 50 ppm ClO2 and 900 and 2,700 ppm H2O2 did not damage most plants tested and will likely control most common pathogen propagules. Rates of 100 ppm ClO2 and 5,400 ppm H2O2 did not damage most plants tested if sprayed less than four consecutive times and should control some of the more chemical-tolerant pathogens.