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Towards a decision-support tool for identifying and mitigating on-farm risks to food safety

Karp, Daniel; Scow, Kate; Jeffery Mcgarvey
University of California - Davis
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Despite ongoing efforts to prevent fecal contamination, fresh produce is a leading cause of foodborne illness (Painter et al. 2013). While widely accepted GAPs (LGMA, 2013) aim to reduce the transmission of foodborne pathogens to produce, growers continue to lack the ability to predict when their crops are at highest food-safety risk as well as effective strategies to mitigate those risks. Moreover, existing practices can be costly and ineffective. For example, our prior research found that, despite widespread implementation (Karp et al. 2015a; Baur et al. 2016), removing non-crop vegetation did not reduce pathogen prevalence on California farms (Karp et al. 2015). Similarly, many growers are replacing compost with synthetic fertilizers or heat-treated manures (Baur et al. 2016), but we also discovered strong relationships between soil organic matter, microbial diversity, and natural pathogen suppression. More generally, while evidence is accumulating regarding the efficacy of many food-safety practices, conclusions are often hidden behind academic paywalls and communicated in forms inaccessible to growers. Our goals are two-fold. First, we seek to synthesize existing literature to develop data-driven, pre-harvest, decision-support tools to help growers predict and mitigate risks associated with foodborne pathogens. Second, we seek to explore novel methods for suppressing foodborne pathogens. Specifically, we will study how soil amendments and management history affect the community dynamics of feces-feeding soil bacteria in order to harness their activity to suppress pathogens. To do so, we will formally review studies that assess how farming practices and surrounding landscapes effect pathogen occurrence or suppression. Rather than committing to a traditional meta-analysis (a sufficient number of studies may not exist for this approach), we will implement a systematic framework for reviewing the efficacy of on-farm practices in which studies are collected, summarized, and then scored by a team of experts (CE, 2018; Dicks et al., 2010). Our experts will include an academic and grower advisory panel so that we can holistically compile information about the cost, feasibility, and efficacy of each practice. Working with our grower partners, we will then synthesize our findings into a web-based, decision-support tool that allows farmers to easily explore the evidence underlying current food-safety practices. To identify novel food-safety practices (Objective 2), we will utilize a 23-year soil experiment to manipulate microbial communities from soils with three distinct management histories: conventional, organic, and mixed (conventional with cover crops). In the lab, we will amend soils of each type with composted manure. We will then monitor changes in microbial communities and pathogen suppression over time, identifying the most effective pathogen-suppression bacteria. Finally, we will leverage existing data to explore how surrounding landscape composition affects soil-based pathogen-suppression. Growers, industry, and conservation organizations have expressed strong interest in making more informed decisions about on-farm practices to improve produce safety without comprising environmental health. By combining literature syntheses and existing data with lab and field experiments, this project will provide growers with both new strategies for mitigating pathogen prevalence and an effective tool to assist growers in navigating decisions regarding the food safety/conservation "stale-mate."

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Natural Toxins
Bacterial Pathogens