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Plant Pathology

Department of Plant Pathology


Water Treatment for Plant Health and Food Safety

Water Treatment Strategies for Plant Health and Food Safety

Extension scientists help growers improve surface irrigation water sanitation methods to reduce plant and human pathogen contamination of fresh produce.


Fresh produce has been implicated in several recent outbreaks of human diseases caused by hemorrhagic E. coli, Salmonella spp. and other foodborne pathogens. Marketing agreements, as well as a new FDA law, are being implemented in order to reduce the risk of contamination of fresh fruit and vegetables by human pathogens.  Vegetable growers in Ohio are being proactive in meeting new requirements; however, there are gaps in understanding the means by which produce becomes contaminated and how contamination can best be prevented.  Irrigation water is a possible source of contamination by human and plant pathogens, but there are no standards for cleanliness for irrigation water or sanitation guidelines.


OSU Extension plant pathologists worked directly with vegetable growers in Ohio to test and determine the levels of contamination of surface irrigation water sources by human and plant pathogens, and the efficacy of commonly used combination fast filtration and chlorine-based treatments in reducing populations of these microbes in water.


In Ohio, Phytophthora capsici is a major limiting factor in the production of pepper, cucumber, winter and summer squash and pumpkin.  We found that P. capsici was present in all ponds and canals used for irrigation water in a major vegetable growing region of Ohio.  We determined that neither chlorine gas nor chlorine dioxide coupled with rapid sand filtration systems were consistently effective in reducing generic E. coli and coliforms in irrigation water to below Ohio recreational water standards.  Further, neither was highly effective in killing Phytophthora capsici zoospores or sporangia.  Based on the studies, an improved multiple barrier sanitation system utilizing chlorine and rapid sand filtration was proposed.  Growers are using OSU Extension resources to modify their current chlorine treatment/sand filtration systems for irrigation water treatment to reduce human and plant pathogen populations, therefore reducing the risks of produce contamination.

Sally A. Miller and Melanie L. L. Ivey, OSU Extension and Department of Plant Pathology

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