Ozone (o3) efficacy on reduction of phytophthora capsici in recirculated horticultural irrigation water

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Title: Ozone (o3) efficacy on reduction of phytophthora capsici in recirculated horticultural irrigation water
Author: McDonald, Garry Vernon
Abstract: 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 .
URI: http : / /hdl .handle .net /1969 .1 /ETD -TAMU -1328
Date: 2009-05-15

Citation

Ozone (o3) efficacy on reduction of phytophthora capsici in recirculated horticultural irrigation water. Available electronically from http : / /hdl .handle .net /1969 .1 /ETD -TAMU -1328 .

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