Sub-objective 1.1. Evaluate microbiological indicators and pathogens (bacteria, viruses and protozoa) in irrigation water both pre- and post-treatment to assess performance of commercially available water sanitizers and pesticide application devices currently used by industry and to provide recommendations towards treatment efficacy and method validation.

Methods:

• Evaluation of water treatment procedure used by industry across the US; including chemical (chlorine, peroxyacetic acid) and physical (UV light) systems using laboratory and field experimentation.
• Evaluation of efficacy of each water treatment method in reducing indicator organisms (i.e. total coliform bacteria, generic E. coli), and pathogens (STEC, Salmonella, Legionella, Cryptosporidium spp., human norovirus/hepatitis A virus), under a range of conditions (i.e., turbidity, temperature, pH, and salinity) representative of a given region.
• Research teams from diverse produce growing regions will follow recently developed US EPA/FDA Agricultural Water Treatment Validation Protocol to assess sanitizer efficacy.
• Following bench-top studies, in-field treatments will evaluate efficacy on agricultural waters under real-world conditions (e.g., flow rate, PSI, etc.).
• Water treatments will be applied in the field to produce plots during multiple growing seasons in region-specific manners (i.e., furrow, drip, overhead, etc.).

 Expected Outcomes:

• Determination of mean log reduction for all indicator/pathogen and treatment combinations.
• Scientific validation of in-field water treatments, with corresponding information on monitoring procedures required to ensure water of adequate sanitary quality for its intended use and/or meet the relevant microbial criteria.

Sub-objective 1.2. Compare survival of E. coli and other select indictor organisms on leaves and fruits post-treatment to provide information for risk assessment and modeling.

Methods:

• Crops grown outdoors in at least two regions of the country.
• Crop leaves and fruits will be sprayed with treated water containing various initial concentrations of generic E. coli as well as other human health organism surrogates, and populations will be enumerated from samples for up to 21 d over the course of two seasons.
• Collection of meteorological data concurrently to assess climate factors and potential re-growth after rainfall events.
• Greenhouse studies will be performed using crop and region-specific practices to evaluate pathogen survival on crops post treatment.

Expected Outcomes:

• Provide information currently lacking related to microbial survival post-treatment.
• Relationships between organisms (pathogen and surrogate) survival can be used to predict survival in the field.
• Provide scientific justification for treated water use during the 21 d before harvest based on the current LGMA requirement.