Microorganisms that cause plant disease have been isolated in recirculated
irrigation water and increase the risks of disease incidence in horticultural operations.
Ozone is an effective oxidizer used to disinfect drinking water supplies and treat
industrial wastewater. The objective of this research was to investigate using ozone gas
as part of a strategy to reduce the incidence of Phytophthora deBary in recirculated
irrigation water. An isolate of Phytophthora capsici Leonian was cultured to induce
sporulation. Spore dilutions were placed in aliquots of reverse osmosis water and
bubbled with ozone gas (O3) to concentrations of 0 to 1.5 mg·L-1. Ozonated samples
were plated and observed for colony forming units.
Increasing ozone concentrations reduced the number of colony forming units to 0
at 1.5 mg· L-1 03. Turbidity effects on efficacy on Phytophthora capsici were tested using
bentonite clay at 0 to 2.0 nephelometric turbidity units and ozone concentrations of 0 to
1.5 mg· L-1. Increasing bentonite did not affect the efficacy of increasing ozone
concentrations on reducing colony formation to 0 at 1.5 mg·L-1 O3. Bioassays using
Phytophthora capsici on Capsicum annuum L. seedlings confirmed apparent
pathogenicity. Reverse osmosis water, containing a soluble fertilizer at 0 to 300 mg· L-1
N, was ozonated to concentrations of 0 to 1.5 mg·L-1 O3 and used to irrigate
Chrysanthemum x morifolium T. de Romatuelle. Increasing ozone concentrations did not
interact with increasing fertilizer levels to affect the final growth parameters.
Chrysanthemum exposed to ozone gas concentrations of 0.5 to 1.5 mg·L-1 showed
symptomatic ozone damage. Complete soluble fertilizer solutions with micronutrients were ozonated from 0 to 1.5 mg·L-1 O3 and analysed for nutrient content. Increasing
ozone levels did not interact with fertilizers to affect macronutrients. Increasing ozone
interacted with iron at a high fertilizer level. Ozone did not affect the efficacy of
paclobutralzol in controlling growth in Viola x wittrockiana. Ozone was effective in
controlling Phytophthora capsici in recirculated irrigation water with minimum impact
on plant growth. Adjustments in fertility regiemes may be needed to counteract the
oxidizing affect of ozone on micronutrients.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-1328 |
| Date | 15 May 2009 |
| Creators | McDonald, Garry Vernon |
| Contributors | Arnold, Michael A., Wilkerson, Don C. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | electronic, application/pdf, born digital |
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