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The overall goals of the proposed research are to determine if there are any correlations between foodborne and plant pathogens in irrigation water used for produce crops; and to evaluate irrigation water decontamination methods for both foodborne and plant pathogens. The objectives of the proposed research are: <OL> <LI>Determine the ultraviolet light inactivation kinetics for plant (Phytophthora capsici, Pseudomonas syringae) and foodborne pathogens (E. coli O157:H7, Salmonella enterica) in different sources and qualities of irrigation water.<LI> Determine ultraviolet light exposure levels necessary to inactivate the most UV resistant pathogen <LI>Identify production capacities required for irrigation systems of varying sizes typical for small to large fruit and vegetable farms <LI> Develop updated training materials (GAPs and GMPs) that focus on irrigation water testing and treatment for fruit and vegetable growers. </OL>The proposed research will assist in the development of a surface water treatment system that controls both plant and human pathogens; ultimately enhancing the safety of produce for consumers while lowering the incidence of plant diseases and improving farm production efficiencies. Currently, chlorination is the only treatment method available for irrigation water and has severe environmental impacts due to repeated, long-term use and accumulation in the soil which renders the soil unsuitable for crops. Ultraviolet light does not alter the water or its composition when treated. The energy demands are also low and solar panels to power the UV processing unit are a possibility.
Non-Technical Summary: Irrigation water serves as a vector for both plant and foodborne pathogens. Microbiological surveys of New York State irrigation water (Bihn, Smart and Worobo) have shown the presence of important plant and foodborne pathogens. Due to different water sources, environmental conditions and location, the quality and safety of the irrigation water can vary dramatically. The presence of either plant or foodborne pathogens in irrigation water represents high risks associated with crop disease or consumer safety, respectively. Currently, there are not widely adopted treatment options for contaminated irrigation water. As a result, fruit and vegetable growers have to identify alternative irrigation sources (if possible) or not irrigate their crops. The proposed research will investigate the ultraviolet (UV) death kinetics of foodborne (E. coli O157:H7, Salmonella) and plant pathogens (Phytophthora, Pseudomonas) in irrigation water of varying sources and quality, when treated with ultraviolet light. A commercial UV processing unit used for unfiltered cider (CiderSure 3500) that is capable of continually adjusting for solids content and turbidity will be used to carry out the treatment. Irrigation water from ponds, streams, and irrigation ditches from 5 different locations in NY state will be used to determine any effects or differences in inactivation rates with the four pathogens. In addition, irrigation water from three different years and seasons (spring, summer, fall) will be tested for the presence of plant or foodborne pathogens prior to UV exposure and after UV exposure to determine overall decontamination efficiency. The results will provide the basis for target UV exposure levels to improve the safety of irrigation water. This will be the basis for the development of a large scale UV treatment system. <P> Approach: Two plant pathogens, Phytophthora capsici and Pseudomonas syringae, and two human pathogens E. coli O157:H7, Salmonella enterica will be used in this study. We will first determine the level of ultraviolet light necessary to inactivate each pathogen in clean, distilled water. Experiments will then be done with multiple different sources of irrigation water, adding known concentrations of each pathogen to the water, treating the water with UV light, and determining the level of pathogen remaining after treatment. This will be done using equipment available in the Worobo and Smart labs, and by plating treated water on selective media that enable the growth of each pathogen. Multiple strains of each pathogen will also be tested to determine if there is variation between strains. Because Phytophthora produces multiple spore types, each different spore type will be tested to determine inactivation kinetics. The next phase of the project will utilize irrigation water collected from five surface sources. Irrigation water will be collected and the level of each of the four pathogens prior to treatment determined by filter-concentrating and plating on selective media. The water will then be treated and again tested for the presence of each of the four pathogens. This will be done multiple times over the course of the season, and over several years. It is crucial to test the UV system at various times in the season and over multiple years because varying environmental conditions will impact the water quality and the pathogen population. While irrigation water is being sampled and tested, the production capacities for irrigation systems will be identified for the determination of flow rates required for UV inactivation or treatment systems to be used at the produce production level. The number of UV lamps, diameter of treatment chambers, and pump sizes will be determined based on the UV exposure required to achieve a 5-log reduction with the most resistant pathogen from both human and plant pathogens tested. Extension materials will be created and distributed during talks at regional meetings and as fact sheets that can be down-loaded from our website.